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SAFETY
/A -A
-A _____ L *-
SERIES
No. 19
The Management of
Radioactive Wastes Produced by
Radioisotope Users
Technical Addendum
INTERNATIONAL ATOMIC ENERGY AGENCY
VIENNA, 1966
THE M A N A G E M E N T OF
R A D IO IS O TO PE W A STE S P R O D U C E D B Y
R A D IO IS O TO PE USERS
TECHNICAL ADDENDUM
The follow ing States are Members o f the International A tom ic Energy Agency:
AFGHANISTAN
ALBANIA
FEDERAL REPUBLIC OF
GERMANY
NICARAGUA
NIGERIA
ALGERIA
GABON
ARGENTINA
GHANA
AUSTRALIA
GREECE
PANAMA
AUSTRIA
GUATEMALA
PARAGUAY
BELGIUM
HAITI
PERU
BOLIVIA
HOLY SEE
BRAZIL
HONDURAS
PHILIPPINES
POLAND
NORWAY
PAKISTAN
BULGARIA
HUNGARY
PORTUGAL
BURMA
ICELAND
ROMANIA
BYELORUSSIAN SOVIET
SOCIALIST REPUBLIC
SAUDI ARABIA
. INDIA
INDONESIA
CAMBODIA
IRAN
CAMEROON
IRAQ .
SENEGAL
SOUTH AFRICA
, SPAIN
CANADA
ISRAEL
SUDAN
CEYLON
ITALY
SWEDEN
CHILE
IVORY COAST
SWITZERLAND
CHINA
JAMAICA
SYRIA
COLOMBIA
JAPAN ’ '
THAILAND
CONGO. DEMOCRATIC
KENYA
TUNISIA
REPUBLIC OF KOREA
TURKEY
COSTA RICA
KUWAIT
UKRAINIAN SOVIET SOCIALIST
CUBA
LEBANON
CYPRUS
LIBERIA
CZECHOSLOVAK SOCIALIST
LIBYA
REPUBLIC OF
REPUBLIC
UNION OF SOVIET SOCIALIST
REPUBLICS
LUXEMBOURG
UNITED ARAB REPUBLIC
DENMARK
MADAGASCAR
UNITED KINGDOM OF GREAT
DOMINICAN REPUBLIC
MALI
MEXICO
REPUBLIC
ECUADOR
BRITAIN AND NORTHERN
IRELAND
EL SALVADOR
MONACO
UNITED STATES OF AMERICA
ETHIOPIA
MOROCCO
URUGUAY
FINLAND
NETHERLANDS
VENEZUELA
FRANCE
NEW ZEALAND
VIET-NAM
YUGOSLAVIA
The Agency’ s Statute was approved on 23 O ctober 1956 by the Conference on the Statute o f
IAEA held at United Nations Headquarters, New York:
Headquarters o f the Agency are situated in Vienna.
It entered into force on 29 July 1957.
the
The
Its principal ob jectiv e is "to accelerate and enlarge
the contribution o f atom ic energy to p ea ce, health and prosperity throughout the w orld".
©
IAEA, 1966
Permission to reproduce or translate the inform ation contained in this publication m ay be obtained
by writing to the International A tom ic Energy Agency, KSrntner Ring 11, Vienna I, Austria.
Printed by the IAEA in Austria
May 1966
.
SAFETY SERIES No. 19
THE MANAGEMENT OF
RADIOISOTOPE WASTES PRODUCED BY
RADIOISOTOPE USERS
TECHNICAL ADDENDUM
IN TERN ATIO N AL ATOM IC EN ERGY AGENCY
VIENNA,, 196,6
International A to m ic E n e rg y A gen cy.
The m anagem ent o f ra d io a ctiv e w astes p r o
duced by ra d io iso to p e u s e r s . T ech n ica l Addendum.
Vienna, the A gen cy , 1966.
81p. (IAEA, sa fety s e r ie s no. 19)
6 2 1 .0 3 9 .7
This Addendum is a ls o published in
F re n ch , R u ssian and Spanish
THE M ANAGEM ENT OF RADIOISOTOPE WASTES
PRODUCED BY RADIOISOTOPE USERS. TECHNICAL ADDENDUM
IA EA , VIENNA, 1966
S T I/P U B /1 1 9
FOREWORD
The In tern ational A to m ic E n e rg y A g e n cy pu blish ed in 1965, as
part of its Safety Standards, a Code of P ra ctice entitled: "The
M anagement of R adioactive W astes P roduced by R a dioisotope U se rs"
(Safety S e rie s No. 12, S T I/P U B /8 7 ), based on the w ork o f two in te r
n ation al p a n els con v en ed by the A g e n c y . T h is A dden du m con ta in s
detailed tech n ica l in form a tion on p r o c e s s e s and p r o c e d u r e s that are
outlined in m o re g en e ra l te rm s in the C ode o f P r a c tic e .
A s in the C ode o f P r a c tic e its e lf, the in fo rm a tio n g iv en in this
A ddendum is p a r t ic u la r ly r e le v a n t to the p r o b le m o f h an d lin g the
r e la tiv e ly s m a ll qu antities o f w aste a r is in g frosri the u se o f r a d io
isotopes in la b o ra to rie s , hospitals and industry when no sp e cia l fa cili
t ie s f o r r a d io a c t iv e w a s te tr e a t m e n t a r e a v a ila b le on th e s i t e .
The A dden du m is d ir e c t e d to w a rd p r o v id in g the r a d io is o t o p e
u se r with the type and amount o f in form a tion re q u ired fo r him to be
able to (a) a s s e s s the a lte rn a tiv e s a v a ila b le to him in te r m s o f h is
p a rticu la r n eed s and r e s tr a in t s , (b) d e v e lo p a p r e lim in a r y d e sig n
of an optim um w aste-handling sy ste m , and (c) get help and guidance
in his s e a rch fo r m o r e detailed in form a tion .
The Addendum has been prep ared by M r. W illiam H. Regan, J r .,
w h ose s e r v ic e s w e re p ro v id e d to the A g e n cy by the G overn m en t o f
the United States o f A m e r ic a , with the a ssista n ce o f the S e cre ta ria t.
The A g e n cy b e lie v e s that th is A ddendum w ill p r o v id e in fo r m a tio n
o f co n sid e ra b le value and pu b lish es it fo r w h atever u se M em b er
States and o th e rs m a y w ish to m ake o f it. H o w e v e r, it sh ou ld not
be regarded as rep resen tin g the A gen cy's o ffic ia l judgem ent o f policy
on the m atter.
CONTENTS
1.
2.
T Y P E S OF W ASTE ASSOCIATED WITH SOME USES OF A
NU M BER OF RADIOISOTOPES ................................ ...................
1
W A S T E -C O L L E C T IO N CONTAINERS AND S Y S T E M S _____ .
4
2 .1 .
2 .2 .
2 .3 .
3.
4
4
5
8
8
10
10
14
18
19
DIRECT DISPOSAL OF RADIOACTIVE WASTES
TO SEW ERS...............................................................................
20
3 .1 .
3 .2 .
21
27
28
30
32
34
3 .3 .
4.
S eg reg a tion .............................................................................
2 .1 .1 .
P h ilo so p h y o f s e g re g a tio n ................................
2 .1 .2 .
M ethods .....................................................................
L iq u id -w a s te c o l l e c t i o n ......................................................
2 .2 .1 .
C o n t a in e r s ................................................................
2 .2 .2 .
M arking and r e c o r d s ...........................................
S o lid -w a ste c o l l e c t i o n ........................................................
2 .3 .1 .
C o lle c tio n -c o n ta in e r d esign and m a te ria ls
2 .3 .2 .
M arking and r e c o r d s ...........................................
2 .3 .3 .
C o lle c tio n and tran sp ortation o n -s ite .........
D isch a rg e p r a c t i c e s .............................................................
Dilution tech n iqu es and c o m p u ta tio n s ............................
3 .2 . 1 .
G en era l c o n s id e r a t io n s ......................................
3 .2 . 2 .
C a lcu la tion s f o r d is p o s a l p r a c t i c e ...............
3 .2 . 3 .
C o n sta n t-d rip d isch a rg e bottle . . . . . . . . . . .
3 .2 . 4 .
R ecom m en d a tion s fo r d i s p o s a l ......................
B eh aviou r o f r a d io n u clid e s in se w a g e -tre a tm e n t
plants ..........................................................................................
LIQU ID-W ASTE T R E A T M E N T TECHNIQUES SUITABLE
FO R USERS OF R A D IO IS O T O P E S ..............................................
4 .1 .
35
37
B a tc h -c h e m ic a l trea tm en t ...............................................
37
4 .1 .1 .
L im e -s o d a ash t r e a t m e n t ..................................
40
4.
1 .2 .
A lum inium and f e r r i c hydroxide coagulation . 41
4 .1 .3 .
P hosphate c o a g u la t io n .........................................
43
4 .1 .4 .
F e r r o c y a n id e p recip ita tion .............................
44
4 .1 .5 .
Strontium phosphate p re cip ita tio n ...............
47
4 .1 .6 .
M a ssiv e c h e m ic a l t r e a t m e n t ...........................
47
49
4 .1 .7 .
T re a tm e n t o f slu d ges ........................................
4 .2 .
4 .3 .
4 .4 .
5.
SO LID -W ASTE T R E A T M E N T AND DISPOSAL BY INDI
VIDUAL USERS OF RADIOISOTOPES ...................................
5 .1 .
5 .2 .
5 .3 .
6.
Ion exchange u sin g
o rg a n ic r e s in s ...................
4 . 2 . 1 , T re a tm e n t by ion e x c h a n g e .................................
4 . 2 . 2 . C ation e x ch a n g er f o r p r o c e s s in g gen era l
la b o r a to r y w astes ................................................
E v a p o r a t io n .............................................................................
4 . 3 . 1 . L o w -te m p e ra tu re e v a p o r a t o r ...........................
4 . 3 . 2 . W ip e d -film e v a p o r a t o r ...................... ...............
C on clu sion s and recom m en d a tion s ....................... ; . . .
I n c in e r a t i o n ............... ..............................................................
5 .1 . 1 . I n tr o d u c tio n ..............................................................
5 . 1 . 2 . A p p l i c a b il i t y ............................................................
5 . 1 . 3 . Sim ple a pproach to ca lcu la tin g safe lim its
fo r in cin e ra tio n .....................................................
C o m p r e s s i o n ..................................................................
S olid -w a ste b u ria l
.....................................................
5 . 3 . 1 . P a ck a gin g .................................................................
5 .3 . 2 . Site s e le c tio n fo r ground d is p o sa l .................
A IR -B O R N E W ASTE MANGEM ENT
6 .1 .
6 .2 .
.........................................
F u m e -h o o d d esign re com m en d a tion s .............................
G aseous and a e r o s o l w aste c o n tr o l sy stem s suitable
fo r use by s m a ll la b o r a to r ie s .........................................
6 . 2 . 1 . H ig h -e ffic ie n c y filt e r s .......................................
6 .2 . 2. M e d iu m -e ffic ie n c y p r e -filt e r s .......................
6 . 2 . 3 . A ctiv a ted ca rb on ad sorb en ts ............................
REFERENCES
50
50
52
59
59
62
64
65
65
65
66
66
69
70
70
72
74
74
76
76
78
78
79
1.
T Y P E S O F W A STE A SSO C IA T E D W ITH SOME USES O F A
N U M BER OF RAD IO ISO TO PE S
Isotope
H a lf-life
A c 227
22 yr
Main use
A ctin iu m -2 2 7 /
Amounts
1 -10 0 m e
beryllium neutron
Type o f waste
None unless source
is broken or lost
sources
Sb124
60 d
( a ) An tim o n y -124 /
102 - 103 c
beryllium
None unless source
is broken or lost
neutron
sources
(b ) As tracer
m icrocu rie
Small hazard
o f m illicu rie
amounts
Ba140
12. 8 d
Tracer in steel
10-5 0 m e
industry
Br80
1. 5 yr
f (a ) Diagnostic
■
j
and
Br82
36 h
J
Remains as in
soluble in slag
~ 10
jj,c
Excreted in urine
use
[ (b ) Industrial
~ 100 m e
Liquids and solids
tracer; e. g.
study o f
retention in
tanks
C s137
30 yr
Sealed sources
1 m e to
None unless source
used in therapy
1000 c
is broken or lost
~ 10 fic
V arious-depending
and radiography
C 14
5760 yr
(a ) Over 200 la b e l-'I
led com pounds.
on type o f
experim ent
(b ) Tracer in
b io lo g ic a l work
C r 51
27. 8 d
C lin ic a l purposes
10 fic
Excreted slowly
per patient
1
Isotope
H a lf-life
M ain use
C o ou
5. 27 yr
(a ) W ide range o f
Amounts
up to 50 c
Type of waste
V ery little use as
sealed sources
an industrial
for radiographic,
tracer; alm ost e n
m e d ic a l or
tirely used as a
gen era l use
sealed source
( b ) Industrial
irradiation.
Up to m e g a
curies
S ealed sources
up to m ega cu rie
le v e l
A uls“
2.7 d
Therapy:
(a ) C o llo id a l
C o llo id a l
Largely retained
m e ta l - up
in patient
to 150 m e
per dose
(b ) "Grains
Grains -
Often le ft in
sources
m illic u r ie
patient but
sealed in
amounts
co u ld con stitu te
platinum
12.2 6 yr
8 .0 4 d
Various industrial
solid waste
V ery varying
gets in to liquid
tracers, etc.
e fflu en t
Diagnosis
1 -5 0 (Jc
and treatm ent
2.26 h
Large proportion
uses: b io lo g ic a l
A p proxim ately 75%
e x cre te d in urine
D iagnosis and
treatm ent, e. g . :
(a ) hyperthyroidism
5 to 10 m e
As for I 131 but
short h a l f - l if e
(b ) thyroid
ca rcin om a
74. 4 d
Industrial
radiography
100 to
reduces hazard
150 m e
Usually 1 to
S ealed sources
10 c
per source
F e"
2
45 d
Diagnosis and
~ 10 jic
research purposes
per patient
S om e e x cre te d
Isotop e
H g 197
H a lf -life
65 h
and
Hg203
47 d
p 32
1 4.2 d
M ain use
Amounts
Rising in im p ort
~ 10 lie
a n ce in diagnoses
per patient
(a ) Diagnosis
Up to 300 |ic
( b ) T reatm en t o f
b lo o d dis
T ype o f waste
S om e e x cre te d
5 to 10 m e
Largely e x cre te d
per dose
in urine
orders
( c ) A gricu ltu ral
Ra226
1620 yr
Up to 100 c
Liquid and solid
research work
waste depending
in clu d in g field
on typ e o f
trials
e xp erim en t
(a ) C lin ic a l
M illic u rie
V aluable expen sive
amounts
clo s e d sources should be little if
any waste
(b ) Industrial - as a
M icrocu rie
M ainly solid
fo il-ty p e source
amounts in
waste
and in certain
sources:
types o f e le c t r o
m icro cu rie
n ic va lves and
amounts in
switches
va lves and
switches
( c ) M anufacture o f
Up to about
M ainly solid
50 m c /k g
waste
S ilt tracer in rivers,
C uries per
V arious, depending
e tc.
op era tion
on typ e o f ex p e ri
lum inous
com pounds
S c 46
84 d
m ent
N a22
2. 58 yr
D iagn ostic tracer
M icrocu rie
for humans
amounts
L argely e x cre te d
3
H a lf-life
Isotope
15 h
Na24
M ain use
Amounts
(a ) Tracer in
M icro cu rie to
T ype o f waste
Liquids and solids;
industry, e. g.
m illic u r ie
When used for
d etectin g leaks
amounts
diagnosis la rgely
in new water
e xcre te d
►
m ains.
(b ) Human d iagnostic
tracer
51 d
Sr 89
Large sca le
100 to 1000 m e
a gricultu ral
per exp erim en t
Liquids and solids
tracer work
28 yr
S r 90
Sealed sources for
1 m e to 1 c
S ealed sources there should be
thickness gauges
little waste
gauges, etc.
p rob lem
8 7.2 d
S 35
A gricu ltu ral
Up to cu rie
Depending on type
experim ents
amounts
o f exp erim en t
(in s e ctic id e s
and fu n gicid es)
2.
2 .1 .
W A S T E -C O L L E C T IO N C O N TAIN ERS AND SYSTEM S
SE G R E G A T IO N
2.1.1.
Philosophy of segregation
The op era tion s o f w aste m anagem ent can be g re a tly sim p lifie d
by the s e g r e g a tio n o f the w a ste s into c la s s e s o f m a t e r ia l in su ch a
w ay that a ll co n stitu e n ts o f any one b a tch ca n be d e a lt w ith in the
sam e way. T his id e a l situation can se ld om be attained in p r a c tic e ,
4
because segregation can in itself be quite a complicated operation
which entails significant costs, and may introduce hazards that will
outweigh the convenience and enhancement of safety intended to re
sult from the segregation. As in other aspects of waste management,
benefits must be weighed thoughtfully against penalties.
Wastes can be divided into classes as shown in Table I. Ad
ditional classes could be added, but the 30 shown in the Table are
those most commonly considered. The particular class into which
a given object will fall will depend upon many circum stances - for
example a "high activity" waste from a laboratory concerned with
measurement of environmental radioactivity might well be regarded
as "possibly active" in an irradiated-fuel treatment plant. An ob
ject regarded as "recoverable" in one establishment might be classed
as garbage in another, and definitions of "bulky", "disposable-on
site" and "physically dangerous" will clearly vary from place to
place.
In classifying wastes thought must be given not only to the wastes
themselves, but to the qualifications and number of the people that
handle them, and to their equipment and procedures. Wastes that
might be a serious problem to an unskilled labourer with a hand
cart would present no difficulty to a trained crew with a shielded
pick-up truck. If wastes are collected frequently, the problems
differ from those arising when there are long periods of accumulation.
When wastes are taken from a radioactive area, they should be
presumed to be active unless shown to be otherwise. This is par
ticularly true in hot laboratories, where paper tissue and even writ
ing paper may become significantly contaminated. The decision as
to what level of contamination should be considered significant for
purposes of classification can only be made locally.
2 . 1. 2.
(a)
Methods
Solids
Segregation should begin at the source. Procedures must be
simple, or they will not be used. In tracer laboratories two waste
containers for individual workers may be used - one marked "active"
and the other "inactive". In laboratories handling larger quantities
of. activity, all waste should be placed in "active" containers. When
incineration is being used, each laboratory should have two corres
ponding bins for active (and, where applicable, inactive) glass and
metal ob jects.
5
TABLE I
CLASSIFICATION OF WASTES FOR SEGREGATION
(1) High activity
Low activity
(2) Long h a lf-life
Short half- life
(3) Solid
Liquid
(4) Combustible
Non- combustible
(5) Acid
Neutral
(6) Aqueous solutions
Organic liquids
(7) Corrosive
Non- corrosive
(8) Bulky (compressible)
Bulky (not compressible)
(9) Physically dangerous (sharp, explosive, fragile, e tc.)
(10) Putrefiable
Possibly active
Gaseous
Alkaline
Not bulky
Not dangerous
Not putrefiable
(11) Recoverable
Non- recoverable
(12) Disposable on-site
Not disposable on-site
(13) Disposable to garbage or sewer
Not disposable to garbage or sewer
The containers should be emptied regularly, and a limit should
be set to the maximum permissible external radiation field emitted
from a container. The contents should be taken to disposal racks
or special areas outside the building, marked "active" or "inactive",
the two sites being physically separated to ensure that mistakes in
collection are unlikely. Collection of active wastes should be carried
out by a different vehicle from the one used for "inactive" solids.
The above technique is applicable to the operation of a laborato
ry, but the same principles apply to any installation, with appropriate
modifications according to the nature and size of the establishment
and the kind of radionuclides being used.
(b)
Liquids
A decision must be made as to the level of radioactive content
below which a liquid will - for purposes of control - be regarded as
"non-radioactive". This will depend on the nature of the sewer
system, local regulations, and the kind of work being done. Design
of facilities must be such that the probability of "active" liquid being
6
put into an "inactive" drain is small, but it must be realized that
such accidents will occasionally happen. Experience shows that
radionuclides do in fact get into the sanitary sewage system of "a c
tive" establishments from time to time even when this is strictly
forbidden.
Organic liquids should be segregated from aqueous solutions,
especially if ground disposal is used. The possibility of the occur
rence of violent reactions or explosions must be prevented - for
example nitric acid and alcohol in the same vessel can cause ex
tensive spread of contamination as a result of a reaction.
When the disposal method in use depends for its success upon
adsorption or ion exchange, the effect of acids, alkalis, complexing
and wetting agents, detergents, e tc ., on the system must be con
sidered. F or example, in a case where a large volume of plain
water with a high total content of radioactive material is being
handled, .together with a smaller volume of a "chemical" waste con
taining a comparatively small total content of activity, it would be
unwise to mix the two streams before treatment or disposal.
When disposals are made in cheap but impermeable containers
such as glass or polyethylene bottles, it is often advantageous to keep
the material in the container rather than to pour it out before disposal.
Many industrial operations have demonstrated the advantages,
primarily in efficiency of operation, of providing separate drainage
systems for storm water, sanitary sewage, various p rocess and
waste stream s, etc. In nuclear installations the use of separate
drainage systems reduces the volume of waste material requiring
special handling and treatment and, at the same time, reduces o c
cupational exposure to radioactivity. Segregation of wastes may
range from the collection of radioactive wastes in specially provided
containers to disposal through specially constructed sinks and drain
lines leading to holding tanks for monitoring and processing. Some
times a combination of the two systems is used.
One of the advantages of collecting waste materials in special
containers is that the volume of m aterial handled at any one time
is greatly reduced. However, because these containers must be ac
curately labelled as to content, this system requires the full c o
operation of laboratory staffs. This type of system is especially ap
plicable to limited laboratory operations involving tracer levels of
radioactivity and small volumes of total solution. Special containers
are also useful in segregating long-lived or more hazardous radio
nuclides that require specialized handling, treatment (decontamin
ation), or disposal.
7
The use of special sinks and separate drainage systems leading
to holdup tanks for monitoring is common in many large facilities.
Such systems permit segregation of low-volume high-activity wastes
from the large-volum e low -activity wastes. The form er require
tank-storage facilities or treatment, whereas the latter in many
cases can be released directly into the environment after monitoring
or dilution with non-radioactive waste streams. In some cases even
the large-volume low-activity wastes may require treatment (chemi
cal precipitation, filtration, ion exchange, e tc.) before discharge
to the environment.
2.2.
LIQUID-WASTE COLLECTION
2 . 2. 1.
Containers
For small volumes of liquid waste which are unsuitable for dis
posal into the sanitary system or the active drain system because
of activity level, half-life, or chemical reactivity, containers sim i
lar to the one shown in Fig. 1 are recommended. This consists of
an 8-litre polyethylene bottle mounted within a 20-litre paint can,
the cover of which has been modified as shown to accept the bottle.
Glass bottles may also be used where organic solvents are present,
which would attack the plastic, but the general use of glass is not
recommended. The use of a drip ring placed around the neck of the
bottle is recommended to reduce the possibility of contamination of
bottle and can surfaces. If certain wastes generated within a labora
tory require segregation from the bulk of the liquid wastes c o l
lected, (for example, organics, hydrochloric acid where subsequent
stainless-steel processing equipment may be involved) the can cover
should be painted a distinctive colour and have printed on it the type
of waste for which it is intended.
Where the size of the laboratory and the volume of waste gener
ated does not warrant a separate active drain system connected to
retention tanks, a small stainless-steel sink mounted in a hood and
draining into a container such as described above has proven useful,
particularly for initial decontamination of heavily contaminated labora
tory ware. Because of the limited capacity of the receiver, run
ning water should not be supplied to the sink, and reagent and wash
water should be applied by means of plastic wash bottles.
The use of a simple liquid level alarm is recommended for the
above application, because of the lack of visibility with, regard to the
container contents. Such an alarm may be constructed as follows:
FIG. 1.
Liquid-waste collection container
Two stainless-steel rods, bent into a hook-shape so that they
will hang over the lip of the bottle, and extending about 10 cm into
it, are connected in series with the coil of a low-voltage sensitive
relay and an appropriate power supply. When the waste reaches the
level of the electrodes, the circuit is completed and the relay closes.
The relay contacts complete the circuit between a power source and
a bell or buzzer, thereby providing a warning signal. If larger col
lection tanks are used, com m ercially available liquid-level indi
cators should be utilized.
If the volume of low-activity waste is too large to be convenient
ly handled by means of small containers, or if it is desired to moni
tor the total effluent from a laboratory before discharge, a retention
tank system may be employed. The volume of these tanks will be
dictated by the waste-generation rate, time required for analysis,
and the rate at which the tank may be emptied, either to the sanitary
drain system if permissible, or to treatment facilities if required.
9
In some circumstances, where only short-half-life radionuclides are
involved, decay time may be a factor in sizing. Two tanks should
always be provided. When one tank is full, flow is diverted to the
other, while the contents of the first are sampled and monitored for
radioactivity level. It is also advisable to interconnect the tanks so
that any .overflow from one automatically spills over into the second.
Materials of construction may be carbon or stainless steel, depend
ing on the chemical characteristics of the waste. The use of mild
steel tanks lined with glass., hard rubber, plastic or chemically re
sistant coatings has been shown to be very practical. Stainless steel,
polyethylene, glass tubing and ceramics are examples of materials
commonly used for the piping system. For low-level wastes where
corrosive substances are absent the use of mild steel pipes coated
with bitumen has.proved to be satisfactory.
2. 2. 2.
Markings and records
In addition to the conventional trefoil radiation warning symbol
and a "radioactive" label as shown in Fig. 1, a tag such as the one
shown in Fig. 2 should be attached to the filled waste container, par
ticularly if the waste is to be held for decay storage or if it is to be
processed and disposed of by someone other than the individual
generating the waste. Each container should be sampled and ana
lysed for activity level and pH. Information provided on the tag
should include the isotope or isotopes present in the waste, approxi
mate quantity, external radiation levels, date, and information con
cerning chemical ch aracteristics,5 as well as additional rem arks
which may be of value to others involved in treating or disposing of
the wastes.
Records should be kept of quantities of radioisotopes disposed,
in order to permit maintenance of an accurate inventory of isotopes
on hand. Examples of radioisotope inventory control forms are
shown in Figs. 3 and 4.
•
2.3.
SOLID WASTE COLLECTION
At any site where radioactivity is handled, a remarkable variety
of solid material becomes contaminated to a jgreater or lesser de
gree. These articles range from ordinary paper, rubber gloves and
laboratory glassware tc» large pieces of equipment a:nd even entire
buildings. The usual practice for handling solid wastes consists of
10
FIG. 2.
Label and tags for marking radioactive waste container
accumulating all hazardous wastes in suitable containers for storage,
shipment, further treatment, or ultimate disposal. In handling these
wastes, provision must be made to safeguard personnel from radio
active hazards and to prevent the spread of contamination. P r o
tective clothing is usually required, masks are worn when inhalation
hazards exist, and radiation surveys are made before and during
handling. Segregation of the wastes into combustible or non
combustible and compressible or non-compressible types as well as
by activity level and half-life may be practiced.
Collection practices for low -level solid wastes usually consist
of distributing suitable containers throughout the work areas to re
ceive discarded contaminated material. These containers are plainly
marked with brightly coloured paint and .radiation symbols to d is
tinguish them from ordinary uncontaminated trash cans. They may
range from small cardboard cartons to 208-litre (55 gal) steeldrums.
11
RADIOISOTOPE IN V EN TO R Y
S e r ia l N o; _________________________________________
Isotope __ ____________
O rd ered by: ________________________________________
Com pound ___________
Date o rd e re d : _______________________________ :______
No. m illic u r ie s r e c 'd
Date r e c e iv e d :____________________________
L ocation of stored isotop e _______________________________________________________________________
R oom s used in: ___________________________________________________________ ________________________
L ocation of sinks used fo r disp o sa l: _____________________________________________________________________________________
PORTIONS REMOVED
Date
No. of
m ic r o c u r ie s
FINAL DISPOSAL OF PORTION REMOVED
Decay
D ry w aste
Sewage
M iscella n eou s d isp o sa l
P u rp ose
/uCi
Date
FIG. 3.
MCi
Date
MCi
Radioisotope inventory control form
Date
Method
AiCi
Date
M O N TH LY ISOTOPE DISPOSITION REPO RT
DEPT.'
__________ Radiology______________________________
AUTHORIZED USER ______________ R. Haas_____________________
This rpport covers the month o f June 1961. Please c om plete this form for all radioactive material you received this month or
have on hand from previous months and return to the Department o f Radiology.
A report is not necessary if there were no isotopes
under your control during the month.
|
| No changes since last report.
ISOTOPES REMAINING FROM
ORDERS RECEIVED THIS MONTH
1
1131
P32
3
C14
PURCHASE
ORDER NUMBER
AMOUNT
ISOTOPE
2
PREVIOUS REPORTS
37143
1 mCi
41178
. 10 mCi
51790
50 ^Ci
4
DISPOSAL
Into
Given to
sewage
patients
TOTAL
system 1
Waste disposal
Lost by
service 2
decay
BIOL
DRY
AMT.
AMT.
AMT.
AMOUNT REMAINING
UNDER YOUR CONTROL
(Carry to next report)
Other disposal’
AMT.
AMT.
METHOD
NO.
AMT.
30
0. 1 mCi
1
125 fiCi
1
215 MCi
2
150 fiCi
2
7. 5 mCi
2
2 .4 mCi
3
10 fjCi
AMT.
1
0. 56 mCi
3
30 jiCi
5
6
7
10 pCi
CO 2
1.1 mCi
0. 045 mCi
3 mCi
4
3
5
5
6
6
7
8
9
9
9
10
10
10
20 MCi
COMMENTS:
2 mCi
1. 6 mCi
335
0. 23 mCi
376
7
30 pCi
8
8
345
4
•4
4
LOCATED IN
ROOM(S) NO.
Isotopes under "Amount Remaining e t c . " are reported the following month under "Isotopes Remaining etc.
orders may be grouped together by isotope when reporting.
Separate
In all cases amounts received plus that carried from the
previous month must equal that disposed plus that remaining under your control.
June 31, 1961
1 Sewage disposal is permitted only if within the limits (MCi/day) set in the Federal Register (T itle 10, Part 20.303) and in
cluded in a circular provided by the Radiation Safety Service.
2 Incineration o f radioactive material in any form or amount is not permitted.
FIG. 4.
Radioisotope inventory control report
FIG. 5.
2. 3. 1.
Solid-waste collection can with removable fibre drum insert
Coliection-container design and materials
Refuse cans with foot-operated lids are particularly suitable
for radioisotope laboratories. These may be lined with removable
fibre-board cartons, plastic or heavy paper bags. Figure 5 illus
trates a stainless-steel slidin g-cover can with its removable 28litre (one cubic foot) fibre drum insert. This unit is less likely to
spread contamination than the container shown in Fig. 6 if the con
tents are dusty, although the latter type of can is less expensive.
Figures 7 and 8 show a larger drum and cardboard carton which
are used for objects that will not fit in the smaller containers, or
in cases where a large volume of waste is being produced in a very
short time. For small quantities of waste produced in glove or dry
boxes, the cartons shown in Fig. 9 have proved useful.
When filled, the tops of the boxes or lids of the cartons and
drums should be sealed with wide masking tape, which has been found
to be the most satisfactory type of sealant for this purpose.
FIG. 6.
"Flip-open" solid-waste can with paper-bag liner
For non-combustible or non~compressible waste such as broken
glassware and sharp metal objects which require a container stronger
than paper, large metal paint pails such as shown in Fig. 10 may be
used. Smaller metal paint cans shown in F ig. 11 may be used for
the same purpose or to contain liquid waste which has been solidi
fied in vermiculite, plaster of paris, cement, etc. For the disposal
of small animal carcasses which contain relatively large amounts of
activity, the 4 litre (one gallon) can has been found suitable. The
carcass is placed in a wide-mouthed one-litre jar filled with formal
dehyde. The jar is capped, placed in the can, and the remaining
space filled with verm iculite or other absorbent m aterial. After
inserting the lid on the can, the package may be handled as solid
waste.
15
FIG. 7.
Large fibre drum of Q. 08 m3 capacity
Large heavy-gauge plastic bags supported inside of 120-litre
(32 gal) refuse cans are widely used for solid-waste collection. The
use of plastic bags for trash containers has several advantages over
the use of cardboard boxes under some circumstances. The waste
material, if wet, may seep through the boxes and contaminate floors,
whereas the plastic bags will provide much better containment of
moist material. If packages are stored in locations exposed to the
weather, it has been found that the plastic bags contain the material
much better than the boxes.
Figure 12 shows a standard 208-litre (55 gal) barrel which is
commonly used for packaging solidified concentrates such as eva16
FIG. 8.
0.1-m3 cardboard carton
porator bottoms and chem ical treatment sludges. They may also
be used for packaging higher level solids where shielding is required,
as shown in Fig. 13. These drums are prepared for the wastes by
pouring concrete around a cylindrical paper or fibre form centred
in the drum. The result is a hollow concrete cylinder. Varying wall
thicknesses are obtained by using different sizes of form s. After
wastes are inserted, the remainder of the drum is filled with con
crete, thereby forming a cap which completes the shielding and seals
the drum. Experience has shown the need for reinforcing bars to
ensure a strong joint between the main body and the cap.
17
FIG. 9.
Small cartons of about 1-, 2 -, and {-litre capacity for use in glove boxes and other confined areas
2. 3. 2.
Marking and records
In general, the comments presented in section 2.2.2. also apply
to solid wastes. Labels such as that shown in Fig. 2 should be af
fixed to the package b efore it is relea sed for further handling.
Because of the non-homogeneity of solid wastes, it is very diffi
cult to obtain a representative sample for analysis. Samples can
sometimes be taken and the activity determined; however, in most
cases volume reduction of the sample is necessary, and this can
lead to the possible loss of volatile radionuclides associated with
the waste. Because of this inherent difficulty, waste containers are
generally only monitored externally to ascertain the need for special
handling or shielding. In view of these considerations, records
should be kept of the type and estimated quantity of activity placed
in the container wherever possible.
18
FIG. 10.
Large metal paint pails with about 40- and 20-litre capacity, which may be used for collecting
non-compressible or non-combustible waste
2. 3. 3.
Collection and transportation on-site
Several installations utilize large steel bins, which are designed
for rapid attachment and unloading using special trucks, for the col
lection of filled waste containers and for their transport on-site
(Fig. 14). Others use i~t pick-up trucks, 2-§-t stake-body trucks,
or other vehicles.
Each building should have two separate and distinctively marked
collecting points - one for "inactive" and the other for "active" solids.
Packages placed at either station should be monitored, because o c
casionally radioactive material will find its way into an "inactive"
can. It is usually convenient for laboratory staff to carry active
solid waste to the collecting point because it is unwise to admit the
crew of the collecting vehicle into a building, especially if low
background counting is done there. Most building contamination o c curs through the tracking of radioactive dust on the feet, and the
laboratory staff are likely to be more sensitive to such risks in their
own area than are the crew of the active waste truck.
19
FIG. 11:
Small cans of about 1- and 4-litre capacity
The vehicle used for collecting radioactive waste will sooner
or later become contaminated. It must be an absolute rule that no
package placed at the "active" collecting point be contaminated on
the surface with removable radioactive material. This may require
that some objects be wrapped in polyethylene film or paper, but this
must be done not only to protect people handling the waste but also
to prevent loose contamination from being detached during transfer.
However, with all precautions accidents do happen. It is therefore
advisable to have the vehicle lined with some easily disposable, cheap
material such as plywood, which can be discarded when it becomes
contaminated. Decontamination of an unprotected vehicle is expen
sive, difficult and time-consuming, and during decontamination the
vehicle is out of use.
3.
DIRECT DISPOSAL OF RADIOACTIVE WASTES TO SEWERS
F or small quantities of soluble radioactive wastes containing
nuclides of short half-lives, the most convenient and generally the
20
FIG. 12.
Standard 55-gal (208-litre) barrel used to contain solidified waste concentrates
most practicable procedure is disposal into the sanitary sewerage
system. This provides a period of delay for decay before the radio
active materials can reach water or food supplies, and provides
some degree, of dispersion and dilution.
3.1.
DISCHARGE PRACTICES
Several countries have establishe'd guides or limits for the dis
charge of radioactive wastes to sewer system s. For example,
United States regulations require that (1) the m aterial be readily
soluble or dispersible in water; and (2) the quantity of any licensed
or other radioactive m aterial released into the system in any one
21
FIG. 13.
Shielded container made from standard barrel
day does not exceed either (a) the quantity which, if diluted by the
average daily quantity of sewage released into the sewer by the in
stallation, will result in an average concentration equal to the 40-h
occupational M PC's, or (b) ten times the quantity of such material
specified in Table II, whichever is the larger amount. The regulations
further require that the quantity of any radioactive material released
in any one month, if diluted by the average monthly quantity of water
released by the installation will not result in an average concen
tration exceeding the 40-h occupational M PC's and that the gross
quantity of radioactive material released into the sewer system by
the installation does not exceed 1 C i/y r . The following examples
illustrate the calculations which are made in conducting disposal to
sewers under the above regulations:
Isotope to be disposed of: 131I
40-h MPCW: 6 X 10'5 ,uCi/ml
Table II value: 10/^Ci
22
FIG. 14.
Transportable steel bin for collecting solid wastes
Case A - average daily sewage flow from installation = 15 000 litres
Under 2 (a); 6 X 10'5 /uCi/ml * 10? m l/l X 1. 5 X 104 1/d =
900 MCi/d
Under 2 (b); 10X 10 /tic/d = 100 nCi/d
Therefore, installation could dispose of up to 900 juCi of 131I/d.
Case B - average daily sewagfe flow = 1000 litres
Under 2 (a); 6X10-5 X lO&X 103 = 60 /uCi/dUnder 2 (b); 10X 10 mCi/d = 100 /uC i/d
Under these circum stances, installation could operate under
2' (b) and dispose of up to 100 nC i/d .
However, under the further restriction that the monthly d is
charge not-exceed-MPCw when diluted with the average monthly flow
of sewage, the installation would be limited to 1800 /uCi/month rather
23
TABLE II
SPECIFIED RADIOACTIVE MATERIAL
Material
(fiCi)
Material
(fiCi)
105Ag
1
103Pd + 103Rh
50
m Ag
10
109 Pd
10
I6A s,71As
10
10
147Pm
210po
10
198Au
199Au
u°Ba +U0La
10
143Pr
10
1
239Pu
1
ê
50
226Ra
0.2
0.1
14C
50
86Rb
10
^Ca
10
186Re
10
105Rh
10
109Cd + 109Ag
10
144Ce + 144Pr
1
106Ru + 106Rh
3<C1
1
35 s
60Co
1
124Sb
51Cr
50
46Sc
137Cs + 137Ba
1
1
50
1
1
153sm
10
u3Sn
10
«Cu
50
154Eu
18p
1
50
“ Fe
50
182T a
10
59Fe
1
96Tc
1
12Ca
10
» Tc
71Ge
50
127Te
250
i» ie
114In
1
192Ir
10
+
10
1
>*
13 l j
CO
sH(HTO or’ HjO)
89Sr
Th (natural)
204T1
Tritium. See H3
42k
10
U (natural)
140La
10
233u
52Mn
1
234y _ 235 y
56Mn
50
48v
99M o
10
185w
22Na
10
90 y
MNa
10
91y
95Nb
10
ffiZn
59Ni
1
63Ni
32 p
1
24
10
0.1
1
10
1
50
50
250
50
1
50
1
10
1
1
10
Unidentified radioactive materials or
any o f the above in unknown mixtures
0.1
than the 3000 ^C i which would be d is ch a rg e d if the in sta lla tion d is
p osed o f the m axim u m allow ed under 2(b) e v e r y day.
W h ere a com bin a tion o f is o to p e s is in v olv ed in known am ounts,
the lim it fo r the com b in a tion should be d e riv e d by d eterm in in g , fo r
each iso to p e , the ra tio betw een the quantity p re sen t in the com b in a tion
and the lim it o th e r w is e e sta b lis h e d fo r the s p e c if ic is o t o p e a lo n e ,
e x p r e s s e d as a fr a c t io n . The su m o f su ch fr a c t io n s f o r a ll o f the
is o t o p e s in the c o m b in a t io n m a y not e x c e e d " l " ( i . e . , " u n it y " ) .
The United States R egulations s p e c ific a lly exem pt e x c r e ta fro m
individuals undergoing m e d ica l d iagn osis o r therapy with ra d ioa ctiv e
m a te ria ls fro m th ese reg u la tion s.
The S oviet U nion's health and safety regu lations g overn in g w ork
with ra d io a ctiv e m a te r ia ls and s o u r c e s o f io n izin g ra d ia tion e s ta b
lish e s d isch a rg e lim its fo r d isp o s a l to s e w e r s . The follow in g p a ra
graphs rep rod u ced fr o m these regu lations apply:
P aragrap h 98
"L iq u id and solid w astes fr o m in sta lla tion s shall be c o n sid e re d
ra d ioa ctiv e i f th eir a ctiv ity (in C i/l it r e and C i/k g ) is m o r e than 100
tim es the m axim u m p e r m is s ib le co n ce n tra tio n in open w ater (C i/lit r e
in the c a s e o f m a t e r ia ls with a h a lf- lif e o f up to 60 d, o r m o r e
than ten tim es the m axim um p e rm is s ib le con cen tration in open w ater
in the ca se o f m a te ria ls with a h a lf-life o f o v e r 60 d ".
P aragraph 138
"W aste w a ter fr o m in stallation sh ow ers and lau n d ries and fro m
the washing o f flo o r s and w alls, e tc. m ay be d isch a rg ed into the
n orm a l sew age sy ste m p rov id ed that its a ctiv ity , without p r e lim in
a ry d ilu tion , d o e s not e x c e e d the le v e ls in d ica te d in p a ra g ra p h 98
and p ro v id e d that a ten fold d ilution by n o n -r a d io a c tiv e w aste w ater
is en su red in the in s ta lla tio n 's c o lle c tin g tank. W a ste w a te r r e le a s e d
d ir e c tly into b od ies o f w ater m ust not contain m o re a ctiv ity than the
m axim um p e r m is s ib le con cen tra tion s fo r open w a ter. "
P aragra p h 163
"S o lid and liqu id r a d io a c tiv e w aste p ro d u cts con ta in in g s h o r t
liv e d is o t o p e s with a h a lf life no g r e a te r than 15 d a y s a r e kept fo r
a tim e that w ill gu a ra n tee a d e c r e a s e in the a c tiv ity to the v a lu e s
in dicated in p aragrap h 98, a fte r w hich so lid ra d io a ctiv e w aste p r o
25
ducts are rem ov ed with the usual rubbish, and liquid waste products
a re d isp osed o f in the sew era ge (see paragraph 138) after being o f
fic ia lly re g is te r e d with the a p p rop ria te r e p o r t ."
R egulations in the United Kingdom provide fo r the establishm ent
o f d is ch a rg e lim its on a c a s e - b y - c a s e b a s is by the a p p ro p ria te
a u th orities b e ca u s e o f w id e ly d iffe r in g lo c a l c o n d itio n s .
In a governm ent publication entitled "T he C ontrol of R adioactive
W a s te s ", C-MND 884, b ro a d p r in c ip le s co n c e r n in g w aste m a n a g e
m ent are stated and som e g e n e ra l guidance given . The follow in g is
a section of this docum ent dealing with disch arge of rad ioactive waste
to s e w e r s .
, .
"in the c a s e o f d is c h a r g e s to s e w e r s the fo llo w in g c o n s i d e r
ation s a r is e :
.
(i) the con tam in ation o f the drains, w hich m ight p re se n t a h a za rd
d u rin g r e p a ir p r o c e s s e s ;
(ii) the con ta m in a tio n o f the se w a g e i t s e lf w h ich c o u ld e n d a n g e r
m en w ork in g in the s e w e r ;
(iii) the con tam in a tion o f the p u rifie d sew a ge e fflu en ts w h ich m ay
- a ffe ct th e ir u ltim ate d is c h a r g e ;
*
(iv) the b u ild -u p o f'r a d io n u c lid e s on filt e r b e d s .
( v ) the p o s s ib le u se o f sew age slu d g e .
i" E a ch ra d io n u clid e d is c h a r g e d m ay w e ll behave d iffe r e n tly and
con tribu te to one o r m o r e of the above potential hazards-. In c o n s e
qu ence, the fixin g o f g e n e ra l •lim its is not. ea sy, but a le v e l
of 10‘4 m C i/m l in the sewage flow from the user establishm ents would
n o rm a lly be p e r m is s ib le . E xcep tion s would have to be m ade in the
ca se of the m ore hazardous isotop es o r, fo r exam ple, where a la rg e
fa c t o r y o r h osp ita l d ra in s to a s m a ll’ v illa g e sew a ge w o r k s .
A s to the use of sew age sludge as; a fe r tiliz e r , there is evidence
that th ose ra d io n u clid e s , such as ra d io stron tiu m , w hich a re taken
up r e a d ily by p lan ts, a r e not a d s o rb e d on the slu d g e to any g re a t
ex ten t.
’
The above su g g ested le v e l o f 10 '4 ju C i/m l in the d is c h a r g e a s
su m es a hundredfold dilu tion in the m ain s e w e r " .
The In tern a tion a l C o m m is s io n on R a d io lo g ic a l P r o te c tio n , in
th e ir p u b lica tion N u m ber 5, s ta te s: "V a lid e stim a te s o f qu antities
o f ra d io a ctiv e w a stes fr o m oth er s o u r c e s , in cluding h o sp ita l la b o
ra to rie s, which may app rop riately be relea sed into sew erage s y s
tems- should be based on lo c a l fa c t o r s . Under con ditions r e p r e s e n
tative of m o st s m a ll la b o r a t o r ie s and o f h o s p ita ls u sin g d ia g n o s tic
quantities of ra d ion u clid es, p e r m is s ib le d is ch a rg e s w ill co rre s p o n d
to con cen tration s (a v e ra g e d .o v e r, say, 1 month) in the range of 10-4
26
to 10-5 /u C i/m l in the efflu ent fr o m the e sta b lish m e n t. Such le v e ls
w ill usually be su fficien t to allow d isp o sa l of the w astes which a r is e .
Even with m o re active w a stes, r e le a s e to the sew era ge sy ste m m ay
be a c c e p ta b le , fo r e x a m p le , îf the s y s te m d o e s not d is c h a r g e to a
p oten tia l s o u r c e o f d rin k in g w a te r. On the oth er hand, so m e uses*
o f w a te r m a y r e q u ir e ev en lo w e r c o n c e n tr a tio n s o f r a d io n u c lid e s
than d oes use fo r drinking w a ter. In su c h -c a s e s , the co n ce n tra tio n
of rad ioa ctivity in the re ce iv in g w ater should 1a lso be co n sid e re d and
rela ted to the u ses o f the w a te r; U ses fo r a g ricu ltu re and in d u stry
should be e x a m in e d ". The IC R P fu rth er sta tes: " D ir e c t d isch a rg e
into the sa n ita ry s e w e ra g e sy s te m is 'p a r tic u la r ly s a tis fa c to r y fo r
the d isp o sa l of e x cr e ta fr o m ‘ patients given ra d io a ctiv e m a te ria ls •'i n
m e d ica l d ia g n osis and th e ra p y ". '
■ ■■ ■ •
"T h is recom m e n d a tio n is m ade b eca u se o f th e ir p u trescen t na
ture and the su itability o f sew era ge sy stem s fo r th eir d is p o s a l. The
re la tio n s h ip s betw een qu an tities o f r a d io a c tiv ity r e le a s e s , r a d io
a ctiv e h a lf- liv e s , and q u a n tities o f sew a ge handled by the s y s te m
w ill u su ally be such as to re q u ire no s p e c ia l p reca u tion s oth er than!
th ose which m ay be n e c e s s a r y to p rotect plu m bers and sew age w o r
k ers near points o f d is ch a rg e . "
•. . . . • •- ;
T o r e s t r ic t the p o s s ib ility b f g e n e r a l sink 'contam in ation ea ch
la b o r a to r y o r grou p o f r o o m s should d e sig n a te 1one sink as a "h ot"sink. Only this sink should be :us.ed fo r first* clea n in g 'of con ta m in -'
ated g la ssw a re (in itia l w ashings -should be c o lle c te d in c a r b o y s ) o r
fo r d is p o s in g o f liq u id w a s te s : It sh ou ld be la b e lle d w ith -ca u tion
tape o r-ta g s both on top and on the d ra in . T ra p s and' p ip e s should
be m on itored b e fo re d is a s s e m b ly fo r r e p a irs to avoid rad iation e x
p osu re o f m aintenance p e rso n n e l by ra d ioa ctiv e m a te ria ls that) have'
been p recip ita ted , a d sorb ed , o r plated on ex p osed 1 su rfa ce s .•
3 .2 .
DILUTION TECHNIQUES AND C OM PU TATIO N S-
-!
1 The United States National C om m ittee on R a d ia tion -P rotection ,
in their'H andbdok 49, has 1published re co m m e n d a tio n s'fo r waste d is
p osa l of 32P and 131I fo r m e d ica l u s e r s . T hese recom m en d a tion s in
la rg e m ea su re a d d re ss th e m se lv e s to the p ro c e d u r e s which iriay be
em p loyed to p ro te ct sew age plant w o rk e r s in c a s e s w h ere la r g e
th era p eu tic d o s e s o f 32P o r 131I a re e m p lo y e d . The fo llo w in g is va
su m m ary o f the d isc u ss io n s and recom m en d a tion s p resen ted in this
...................
' ■
Handbook.'
‘
27
3.2.1.
General considerations
It is not r e a lis t ic to in s is t on d ilu tion o f ra d io a c tiv e w a s te s in
sew a ge to the le v e l e s ta b lish e d as p e r m is s ib le in d rin k in g w a te r .
In g e stio n o f this fluid w ill o c c u r on ly as the re s u lt o f an a c cid e n t,
and the hazard should be co n sid e re d fro m this point of view . In a c
tual p r a c tic e , high con cen tra tion s in pipelin es w ill o c c u r o v e r sh ort
p e r io d s ; the du ration o f such high tran sien t c o n ce n tra tio n s w ill ha
about 30 s . It m ay be a ssu m e d that in the c a s e o f a c c id e n ta l im
m e r s io n in sew a ge, not m o r e than 0. 25 lit r e s would be sw a llow ed
in 30 s. It would be re a so n a b le to a ssu m e fu rth er that this w ill not
happen often and that th e re fo re the in gestion o f a p e r m is s ib le tr a c e r
d ose of the isoto p e could be tolera ted in the a ccid en t. The p e r m is
sible tr a c e r dose of either 32P or i31I is approxim ately 100 mCi; this
would be contained in 0. 25 litre s if the concentration were 0. 4 /u C i/m l.
T o allow fo r an a d dition al m a rg in o f sa fe ty the value fo r m a xim u m
sh ort p e rio d contam ination o f 32P o r 131I in sew age used in the f o l
low in g ca lcu la tio n s is 0. 1 /LtCi/ml (0. 1 m C i/lit r e ).
In the sam e sew age plant an e x te rn a l ra d ia tion h a za rd to plant
p e rso n n e l might be thought to e x ist in ca se o f a ccid en ta l im m e r s io n
in a con cen tration of 0. 1 m C i/lit r e . This con cen tration would be p o s
s ib le , but im p ro b a b le , b e c a u s e o f the dilu tion of the high tra n sien t
co n c e n tr a tio n s in th'e p ip e lin e s by the tim e th ey r e a c h e d the plant
(u n less the institution has its own treatm en t plant). E ven in a c o n
centration as high as 0. 1 m C i/lit r e , how ever, the radiation re ce iv e d
on the s u r fa c e o f the b o d y by su ch im m e r s io n w ould be r e la t iv e ly
low . F o r an im m e rs io n o f one hour, the calcu lated d ose on the s u r
face of the body is 0 .2 rem fo r 32P and 0 .1 rem fo r 1311. If the
slu dge fr o m in stitu tion al o r com m u n ity sew a ge trea tm en t plants is
to be used as a fe r t iliz e r , the hazard to the g en era l population must
be c o n s id e r e d . It m ay be a ssu m ed that the co n ce n tra tio n o f 131I in
the slu dge cake w ill not e x ce e d that o f the sew age as r e c e iv e d , and
that th is co n ce n tra tio n w ill be re d u ce d depending upon the tim e in
v o lv e d in d ig e stio n , con d ition in g, filtr a tio n and sto r a g e o f slu d g e .
At this le v e l the danger fro m e x p osu re to the fe r t iliz e r is ob viou sly
l e s s than that to the se w a g e plant w o r k e r . F r o m the a b o v e c o n
sid e ra tio n s, it appears that the lim itin g fa c to r in the d eterm in a tion
o f the quantity o f ra d io a ctiv e is o to p e s that m ay be d isch a rg e d daily
to a sew age treatm ent plant w ill be the rate of w ater flow at the plant.
The sim p le st way to d is p o se o f r a d io a ctiv e w astes en coun tered
in con n ection with the a d m in istra tion o f the m a te r ia l to patients is,
28
o f c o u r s e , to a llow the patient to u se the to ile t without r e s t r ic t io n .
T h is w ill be c a lle d to ile t d is p o s a l. An a lte rn a tiv e is to p o u r the
ra d ioa ctiv e m a teria l into the sink. In this ca se it m ay be p re fe ra b le
f i r s t to put it into a 4 - l it r e (one g a llo n ) b o ttle , f i l l th is to the top,
u sing tap w ater if n e c e s s a r y , and pour this into the sink. T his w ill
be ca lled b a tch -b ottle d isp o sa l. The batch d is p o sa l (toilet o r bottle)
o f a sin g le sa m p le takes fr o m th re e to 30 s; by the tim e it a r r iv e s
at the sew a ge plant it m a y be c o n s id e r e d as d ilu ted w ith the p r o
p ortion a l part o f the 24~h sew age flow . In an institutional o r m uni
c ip a l s y s te m h avin g an a v e r a g e d d r y -w e a th e r flo w o f on e m illio n
gallon s (3800 m 3) a day at the treatm en t plant, the flow in fou r
se c o n d s is about 100 l i t r e s . T h is w ill d ilute 10 m C i to a c o n c e n
tration o f 0 .1 m C i/lit r e , which has been shown above to be without
p r a c tic a b le h a za rd to plant p e r s o n n e l. W h ile it w ould be e x p e cte d
that this con cen tra tio n would be fu rth er re d u ced in trea tm en t tanks,
it m ight again be in c r e a s e d in slu d g e c o n c e n tr a tio n . F o r la c k o f
a c c u r a te data on th e se p o in ts, it is fe lt w is e at p r e s e n t to set the
lim it o f 10 m C i f o r a s in g le b a tch d is c h a r g e , p e r m illio n g a llo n s
(3800 m 3) o f flow a d a y. In any c a s e w h ere the d a ily d is c h a r g e o f
32P and 1311 ex ce e d s 10 m C i/d p er m illio n gallons of sew age flow the
d is p o s a l should be m ade in s m a ll b a tch e s at in tervals,, o r through
a con stan t head o r i f i c e o r s im il a r m ea n s to m a in ta in a r e la t iv e ly
u n ifo rm d is c h a r g e o v e r a p e r io d o f six daylight h ou rs a day o r lo n g e r .
One such d e v ic e is the constant d rip d is c h a r g e bottle d e s c r ib e d b e
low , and show n in F ig . 15. W ith the in s ta lla tio n and o p e r a tio n o f
su ch a u n ifo rm d is c h a r g e d e v ic e , 100 m C i o f th e se is o t o p e s m a y
be d isch a rg e d in any s ix -h o u r daylight p e rio d into a sy ste m having
a o n e -m illio n -g a llo n a v e ra g e d r y -w e a th e r flo w . The p e r m is s ib le
d isch a rg e s fo r oth er sew age flow s w ill be p ro p o rtio n a l to the above,
e . g . , 50 m C i fo r 0 .5 m illio n ga llon s (1960 m3) d aily.
The a bove lim its a re s u b je ct to r e v is io n in any com m u n ity on
the ba sis of actual ra d ioa ctiv e m easu rem en ts in the slu d g es. W here
qu an tities o f r a d io a c tiv e is o t o p e s o f the o r d e r s u g g e s te d b y th e se
lim its are d isch a rged , ra d ioa ctiv e m easu rem en ts o f the sludge should
be made and the lim its re v ise d , if n e c e s s a r y . R esp on sib le o ffic ia ls
at institutions using co n sid era b le quantities (100 m C i o r m o re a week)
o f r a d io a c t iv e is o t o p e s , should in fo r m and c o -o p e r a t e w ith m u n i
cip a l and reg io n a l health a u th orities, in o r d e r that p r o p e r a rra n g e
m en ts fo r m o n ito rin g m ay be m ade when th e re is any q u e stio n r e
g ard in g sa fety o r h a z a rd .
29
■FIG. 15..
3. 2. 2.
4 -litre :bottle set-up for constant-pressure drip discharge.
'
Calculations for disposal practice
'
On the b a sis o f the above d iscu sse d gen eral con sid era tion s, f o r
m u las have b e e n d e v e lo p e d '‘fo r com pu ting p e r m is s ib le d is c h a r g e o f
32p o r 1311 b y v a r io u s m eth od s,, in s y s te m s with d iffe re n t a v e r a g e
w a ter flo w s . C a lcu la tio n s b a se d on th ese fo r m u la s fo llo w :
'
"'.V'
N™ = M /q
•
•
f •_
(IV
wheire Nm = maximum contamination'Occurring iri a Water column
flowing through the sewer (/LtCi/litre),
M
= activity, in m ic r o c u r ie s , introduced in a sin gle d isp osa l
event,
q
- w ater u sed during a sin gle d is p o s a l event; fo r to ile t
flush ing, q .=12 to' 3 2 litr e s.
(a) T r a c e r and th e ra p e u tic dose's u p ’to 1 1 m C i. L e s ’s than 25% is
u su a lly e x c r e te d , d u rin g the fi r s t day, arid th is o c d u r s in not
l e s s than in four ev a cu a tion s. M 'is , th erefore, usually not m ore
than 6% of the adm inistered d ose, o r 60 /uCi.
30
The m axim um contam ination that can o c c u r i f on ly flushing w ater
is co n sid e re d is calcu lated fro m E q .( l ) :
Nm = 2X lO -3 to 5X 10 "3 juC i/m l
(b)
i . e . , b e lo w p e r m is s ib le le v e l o f 100 /j C i /l i t r e (0 .1 )LtCi/m l).
T h era p eu tic d o s e s o f 32P .
The la r g e s t s in g le d o s e u sed at
p re se n t is 7 m C i. T his re s u lts in M equals 420 juCi ( 6% o f ad
m in iste red d o s e ). A gain co n sid e rin g to ile t-flu sh in g w ater alone
1
we get fro m equation ( 1 ):
Nm = 0 .0 1 3 to 0. 035 AiCi/ml
(c)
i . e . , a lso below p e r m is s ib le le v e l.
131I in treatm en t o f h y p e rth y ro id ism . A sin gle d o s e w ill r a r e ly
e x c e e d 10 m C i. In c a s e s o f h y p e rth y ro id is m r e q u ir in g su ch a
high d o s e , the fir s t 24~h e x c r e tio n w ill be not m o r e than 30%,
and it m ay be a ssu m ed that not m o re than half w ill be evacuated
at one tim e : M eq u a ls 1. 5 m C i. M axim um con ta m in a tion that
w ill o c c u r , if only flushing w ater is c o n sid e re d ca lcu la ted fro m
equation ( 1 ):
Nm = 0. 047 to 0. 125 £iC i/m l
i . e . , s till e sse n tia lly at p e r m is s ib le le v e l.
T reatm ent of thyroid c a n ce r. A single d ose o f 100 m C i is r a r e
ly e x c e e d e d . H ow ev er, when uptake by m e ta s ta s e s is low and
th y ro id e cto m y has been p e rfo rm e d , up to 90% m ay be e x cre te d
within the fir s t 24 h. A gain M is equal to h a lf o f th is va lu e: ,M
equals 45 m C i. C o n sid e ra tio n o f flushing w ater alone w ill lead
to e x c e s s iv e v a lu e s o f N m . T a k in g in to a c co u n t the a v e r a g e
w a ter u se o f 550 lit r e s p e r p e r s o n p e r day, v a r ia tio n s in flow
d u rin g d ay and night, and u s in g 100 fxC i / l i t r e a s the lim itin g
c o n c e n tr a tio n , (N m ), T a b le III w a s p r e p a r e d .
F o r the d is p o s a l o f la r g e r q u a n tities the c o n s t a n t -d r ip b o ttle
d e s c r ib e d b e lo w m a y be u s e d . The la r g e s t am ount that can be e x
creted by one patient p er day w ill seldom exceed 100 m C i. It is p e r
m is s ib le to d is c h a r g e this amount by the constant d rip b ottle, p r o
vided the d ry -w e a th e r flo w to the sew age treatm en t plant is one
m illio n g a llon s p e r day o r m o r e .
(d)
31
TABLE III
PERMISSIBLE ACTIVITIES IN MILLICURIES FOR
SINGLE DISPOSAL EVENTS
Toilet disposal
Number o f beds
disposal day*3
Night
Day
(mCi)
(mCi)
(m Ci)
■
Batch bottle
Number o f people a
25
50
1 to
4
1 to
3
1
50
100
2 to
4
1 to
4
2
100
200
2 to
5
2 to
4
4
200
400
2 to
6
2 to
5
8
300
600
2 to
8
2 to
6
12
500
1000
4 to 11
2 to
8
20
2000
6 to 20
4 to 13
40
1000
a It is assumed that the hospital population is equal to twice the number of beds,
b Batch discharge o f a full 4-litre bottle (add tap water if necessary) emptied into a sink, not
into a toilet.
3. 2. 3.
Constant-drip discharge bottle
A sim p le d e v ic e fo r d is ch a rg in g 4 lit r e s (one g a llo n ) o f liqu id
w aste at a con sta n t ra te is illu s tr a te d in F ig . 15. It c o n s is t s o f a
4 -lit r e jug and a tw o -h o le sto p p e r with two g la ss tu b es. One g la ss
tube (a ir in let tube) r e a c h e s to about 6 cm above the b ottom o f the
b o ttle . The secon d glass, tube (outflow tube) r e a ch e s to the b ottom .
A ru bber tubing is attached to this outflow tube, and a ca p illa ry glass
tube is attached to the oth er end of the ru b b er tubing. The ca p illa ry
tube is attached to the bottle (with w a t e r -p r o o f tape o r a d h esive
p la s t e r ) so that the top o r i f i c e o f the c a p illa r y is 5 c m b e lo w the
lo w e r end o f the a ir - in le t g la s s tu b e.
W hen the b ottle is fille d and the sto p p e r with the tu bin gs in
sta lled , it m ay be set in a sink and the flow started by pum ping a ir
into the open end o f the a ir - in le t tu b e. T h is m a y be c o n v e n ie n tly
done by attaching a p ie ce o f ru bber tubing to this open end and using
32
C A P ILLA R Y DIAM ETER (mm)
FIG. 16.
Length of capillary tube as a function of its diameter for an emptying time of 6 h for a 4 -litre bottle
with a water-head of 5 cm
the inflating ru b b er bulb with the r e le a s e valve o f a b lo o d -p r e s s u r e
m o n o m e te r. A fte r the liqu id b eg in s to flow fr o m the c a p illa r y the
flow w ill be m aintain ed by syphon a c tio n . The p r e s s u r e is d e t e r
m ined by the le v e l d iffe re n c e betw een the lo w e r end of the a ir -in le t
tube and the c a p illa r y o r if ic e (this le v e l d iffe r e n c e is m a d e eq u a l
to 5 c m ). The p r e s s u r e w ill re m a in constant until the liq u id le v e l
in sid e the b ottle d ro p s below the end o f the a ir -in le t tube; then the
p r e s s u r e w ill g ra d u a lly d rop until the le v e l sin ks b e lo w the end o f
the outflow tube.
F lo w -r a te is d eterm in ed e ss e n tia lly by this p r e s s u r e and by the
length and inner d ia m eter o f the ca p illa ry tubing. Suitable ca p illa ry
tu bes with an in n er d ia m e te r b etw een 4 and I 4 -m m a r e g e n e r a lly
available fro m la b o r a to ry equipm ent d e a le r s . F ig u re 16 is an e m
p i r i c a l p lot in d ica tin g the r e q u ir e d len gth s o f c a p illa r y tube o f
v a rio u s in n er d ia m e te r s , fo r a flo w ra te at w hich the b ottle w ill be
em p tied in 6 h.
The actual em ptying tim e with the set-up d e sc r ib e d w ill g e n e ra l
ly be within about 30% o f 6 h, b e ca u se o f a num ber o f fa c t o r s which
it is d ifficu lt to co n tro l (fo r in sta n ce: change of v is c o s ity with te m
p eratu re, v a ria tion s o f the b o r e o f the sam e ca p illa ry , e t c . ) . This
uncertainty in em ptying tim e, h ow ever, is sa tisfa cto ry fo r p ra ctica l
p u rp oses.
33
3. 2. 4.
Recommendations for disposal
A fte r the daily o r w eekly w a s te -d is p o s a l le v e l fo r an institution
has been d eterm in ed , the m ethod o f d is p o s a l m ust be d e cid e d fr o m
con sid era tion s o f safety both to sanitation w o rk e rs and sew age-plan t
p erson n el. It has been pointed out that fo r the first, a transient con
ce n tra tio n o f 0. 1 m C i /l i t r e should be p e r m is s ib le , w h ile f o r the
secon d , a s in g le -b a tc h d is ch a rg e o f 10 m C i, o r a 6~h constant d is
c h a rg e o f 10 m C i, p e r m illio n g a llo n s (3800 m 3 ) o f w a te r flo w is
s a t is fa c t o r y .
The values tabulated in Table III fo r institutions o f various s iz e s
a re va lid p ro v id in g the d r y -w e a th e r flo w to the s e w a g e -tr e a tm e n t
plant equals o r e x ce e d s a m illion gallons a day fo r each 10 m C i d is
ch a rg ed . If the flow to the se w a g e -tre a tm e n t plant is not g rea t
enough to p e rm it the u se of T able III, a co n sta n t-d rip b ottle should
be u sed , on the b a s is o f a 100 m C i d is c h a r g e d in this m a n n er p e r
m illio n g a llon p e r day w a te r flo w to the s e w a g e -tr e a tm e n t p lan t.
T hus, fo r le s s than 10 m C i the lim itin g fa c t o r is tran sien t c o n c e n
tration in pipeline, as determ ined fro m the Table; fo r la r g e r amounts
the lim itin g fa c t o r m a y be co n c e n tr a tio n at the se w a g e plant to be
d e te rm in e d by to ta l d a ily flo w to this plant.
3. 2 . 4 . 1 .
S m all quantity d is p o s a l
In d ia g n o stic and th era p eu tic u se s o f 32P , in d ia g n o s tic u se o f
1311, and in trea tm e n t o f h y p e r th y r o id is m with 131I, p a tie n ts m a y
u se the to ile t without any in s tr u c tio n s o r r e s t r i c t io n s .
3. 2. 4. 2.
A.
C a r c in o m a tre a tm e n t with 131I
H o sp ita ls
It is not p o s sib le to form u late sim p le in stru ction s fo r the le v e ls
e x c r e te d in the trea tm en t o f c a r c in o m a ; m illic u r ie s e x c r e te d by a
p a r tic u la r patient m u st be c a lcu la te d on the b a s is o f d o s e and u p
take, and m ethod o f d is p o s a l m u st be d e c id e d fr o m T a b le III.
When the quantities fo r d isp o sa l e x ce e d the p e r m is s ib le v a lu es
e ith er fr o m T able III o r fr o m the g e n e ra l sew a ge-p la n t lim ita tio n s,
the follow in g m ethods can be used:
(1) S torage fo r d e ca y to p e r m is s ib le a ctiv ity ;
(2) D is trib u tio n o f a c tiv ity in a n u m b er o f o n e -g a llo n b o ttle s
each containing p e r m is sib le a ctiv ities; fillin g bottles with tap water;
34
s u c c e s s iv e em ptying o f these b ottles in the sink at p r o p e r in te rv a ls,
(batch bottle d isch a rg e );
(3) S ix -h ou r d isp o sa l by co n sta n t-d rip bottle.
In d ecid in g on the use o f one o f the above m eth od s, o r a b a tc h b ottle d is p o s a l in a c c o r d a n c e with T a b le III, ra d ia tio n e x p o s u r e to
la b o ra to ry p e rso n n e l m ust be c o n s id e r e d . T his is a m a tter fo r the
in stitu tio n a l ra d ia tio n s a fe ty o f f i c e r and o u tsid e the s c o p e o f th is
s e c tio n .
B.
A p a rtm en t h o u s e s and s m a ll h o m e s
On the b a sis o f T able III it would appear that to ile t d isp o sa l
w ould r a r e ly be p e r m is s ib le fo r patients trea ted without h o s p ita li
zation. H ow ever, it m ust be co n sid e re d that in these c a s e s , fo r one
h om e, on ly a sin g le patient is in v o lv e d ; the p r o b a b ility o f s e v e r a l
p erson s in the sam e building being treated fo r ca n ce r with ra d io
a ctiv e is o to p e s at the sa m e tim e is n e g lig ib le . High con tam ination
in the lo c a l sew age s y s te m w ill thus o c c u r se ld o m , w ill be o f b r ie f
du ration , and w ill be p r o m p tly r e m o v e d by fu rth e r flo w o f sew a ge
and by ra d io a c tiv e d e c a y . T h is c o n s id e r a tio n p e r m its r e c o m m e n
dation of sim p le toile t d is p o sa l fo r patients who are not h osp ita lized .
3. 2. 4. 3.
Sim ultaneous d isp o s a l o f 32P and 1311
When 32P and 131I are used sim ultaneously in an institution, d is
p o s a l ru le s can be b a se d on the sum o f the m illic u r ie s o f both
is o t o p e s .
3 . 3 . BEH AVIOU R OF RADION UCLIDES IN S E W A G E TR E A TM E N T PLANTS .
B io lo g ic a l tre a tm e n t p r o c e s s e s a r e ra th e r in e ffic ie n t fo r .th e
rem ov a l of rad ioa ctiv e m a teria ls fro m w ater. T here have been som e
d ire ct d eterm in ation s of the beh aviou r o f ra d io iso to p e s during p r im
a ry se d im en ta tion . V e r y little ra d io io d in e se ttle d out fr o m cru d e
sewage to which had been added urine from patients who'had receiv ed
d ia g n o stic d o s e s . L e s s than 5% a b so rp tio n on p r im a r y slu dge w as
found fo r rad iosod iu m , ra d iocob a lt, radiophosphorus and radioiodine
at con cen tration s in the range o f 0 .5 to 50 ju C i/litre.
35
The most important characteristics determining the behaviour
of a radioisotope in biological purification are its chem ical nature
and the concentration of its inactive isotopes in the sewage. The
active isotopes are normally present in such small concentration
that their presence does not affect the total concentration of isotopes
of that element in the sewage. Consequently, the degree of removal
of a radioisotope, expressed as a percentage of the initial concen
tration of the radioisotope, is independent of that concentration.
The behaviour of several radioisotopes in sewage can be at once
predicted without reference to published experimental work. Tritium
is the radioisotope of hydrogen and will normally be discharged to
the sewers as water or, less often, as organic compounds containing
tritium. The latter will usually be oxidized to water on the filters.
Ultimately the tritium will be flushed out with the effluent or the
sludge and will not remain at the disposal plant. The ionizing radi
ation from tritium is so soft, and the perm issible level in drinking
water is so high that much larger amounts than are commonly used
would be necessary to produce a hazardous level.
Radiosodium and radiopotassium will behave like salt and pass
through the disposal plant. Experimental work has indicated that
radiobromine will behave in a sim ilar fashion. Radiocarbon will
be oxidized and released either as gas or in the effluent and sludge
and no concentration at the plant can occur. Radiosulphur will most
ly be in the effluent. Radiocalcium and radiostrontium also will pass
through.
Most experimental work on the biological behaviour of radio
isotopes has concerned radioiodine and radiophosphorus. Their
behaviour depends largely on the concentration in sewage. For
radiophosphorus, removals as high as 80 to 90% occurred on trick
ling filters at levels of 1 ppm in the sewage, but these fell to 20%
at levels of 6 ppm. With the high phosphorus content of sewage now
common from the use of synthetic detergents, the latter figure is
likely to be more representative of what will be achieved in practice.
Reports of the behaviour of radioiodine on trickling filters are
contradictory. Results range from only 5% removed to 75-90% re
moval. The difference is perhaps attributable to different levels of
inactive iodine in the sewages used by the investigators. Studies
have shown that the proportion removed by the filter depends on this
factor, as with radiophosphorus.
Another radioisotope whose behaviour has been investigated on
trickling filters is radiocobalt. Removal of 80% was observed. It
36
is probable that the behaviour Of radiocobalt, like that of radiophos
phorus and radioiodine, is dependent on the concentration of inactive
cobalt in the same chemical form, and it is not clear how r e
presentative of the general behaviour are the results quoted above.
The removal of radioisotopes by activated sludge is sim ilar to
that by trickling filte rs. Here again the removal of radioiodine ranges
from 90% to only 10-15% removal, again probably due to the con
centration of inactive iodine in the sewage. There is little removal
of radiocalcium, radiosodium and radiobromine. 85% removal of
radiophosphorus and radiocobalt has been reported.
Thus, there is experimental evidence for the behaviour in bio
logical treatment of most of the radioisotopes at present used in
research . There is enough evidence to assess the situation in a
system of sewerage and sewage disposal with sufficient accuracy.
It can be stated confidently that the amount taken up on filters or in
activated sludge is not sufficient to be hazardous to workers. Only
if relatively large amounts of a long-lived radioisotope like cobalt-60
were discharged to the sewers would hazardous levels build up. As
stated in section 2. 1, where quantities of radioisotopes approaching
the permissible limit are discharged to the sewer, sludge measure
ments should be made to assess the validity of these limits for the
particular conditions which exist.
4.
LIQUID-WASTE TREATMENT TECHNIQUES SUITABLE FOR
USERS OF RADIOISOTOPES
4.1. BATCH-CHEMICAL TREATMENT
Most of the chem ical methods involved in radioactive-w aste
treatment are adaptations of standard water-treatment practice, and
have been extensively used for processing large volumes of lightly
contaminated wastes using equipment designed for continuous
operation.
However, it is feasible to utilize batch chemical treatment where
the volumes involved are small, and where the nature of the wastes
points to chemical treatment as the best method.
It is suitable for application where the required reduction of
activity in the waste is small, since decontamination factors (DF)*
^
_
.
.
r
___
co n c . o f radioactivity in feed
D econtam ination factor = DF = ------------- ------------------------L----------------c o n c. o f radioactivity in effluent
37
of more than 10 are seldom attained. If it is possible to select and
optimize the process for a single radioactive species, however, much
better results may be achieved. Advantages of the process are low
cost, the ability to handle a wide range of solid content in the feed,
and in some cases the production of a waste sludge volume which is
relatively independent of feed solids content. Suitable handling, stor
age and disposal facilities, of course, have to be provided for the
resultant radioactive sludge.
Chemical coagulation involves the de-stabilization, aggregation
and binding together of colloids. These colloids form chemical
floes that adsorb, entrap, or otherwise bring together suspended
matter. Commonly used c.oagulants are alum and iron salts, which
are precipitated as aluminium and iron hydroxides.
In chemical precipitation, chem icals are added to produce an
insoluble, somewhat heavy precipitate, which removes radioactivity
as it settles out of solution. The radioactivity may be removed by
direct precipitation, by adsorption on the resultant floes, and by
entrainment in the settling precipitates. Precipitation and floccul
ation may occur simultaneously, as in the case of calcium phosphate,
fe r r ic ion, or lim e-soda treatment, or may involve the formation
of a suspension which requires the subsequent introduction of a floc
culating agent such as ferric hydroxide. Details of these and other
processes are discussed below.
There are three steps in the process of coagulation and
flocculation:
(1) Addition of coagulating chem ical to the liquid waste. To
ensure that the chem icals are distributed uniformly and promptly
throughout the liquid rapid agitation or mixing must occu r. . This
is extremely important; otherwise the coagulant would slowly d is
perse and the initial chem ical reactions would be localized at the
point of coagulent introduction. This may produce reactions other
than those intended.
(2) Coagulation, i .e . complex chem ical and physico-chem ical
reactions and changes occur leading to the formation of finely di
vided precipitating solids. '
(3) By means of gentle agitation of the liquid, flocculation takes
place, i . e . , the finely divided particles contact and adhere to one
another and form progressively larger flo e . This insoluble flocculent
precipitate will then settle out carrying with it the colloidal mater
ials present in the liquid.
38
I
W ell-form ed floe settles at a rate of about 3 m /h (10 ft/h) al
though it is generally advisable to assume a rate of 0. 75 m /h
(2.5 ft/h) to allow for periods of poor flocculation.
In the development of a method of treatment, representative
quantities of the waste material to be treated are collected and are
tested in the laboratory. Most frequently jar tests of one kind or
another are run to determine specific chemicals needed, optimum
quantities required, and conditions necessary to obtain the desired
degree of removal. The apparatus for performing jar tests is shown
in Fig. 17.
FIG. 17.
Apparatus for con d u ctin g jar tests
For a series of tests, a given quantity of the waste, generally
500 ml or one litre, is placed in each of several suitable beakers.
Varying amounts of the necessary chemical or chemicals are added
to the different beakers, and rapid mixing is provided for periods
up to one minute to ensure complete contact between the wastes and
the chemicals. Then the stirrer speed is reduced to permit maxi
mum precipitate formation. This slow stirring may be continued
for approximately 30 mlji after which the precipitate is allowed to
settle. Samples of the waste before treatment are compared with
aliquots of the supernatant after treatment to determine the con
ditions under which maximum rem oval of activity occu rs. These
findings then serve as the basis for chemical additions under fullscale conditions.
39
With regard to equipment for batch-chemical treatment, the main
requirements consist of a collection tank, where wastes are accumul
ated for treatment, and a treatment tank with steeply sloping conical
bottom section-on which a stirring device is mounted. The chemicals
are added to the waste in the tank and the mixture is stirred rapidly
for 1 to 10 min, then stirred slowly, for a longer period (10 to
60 min). After the stirring has been completed and good flocculation
achieved, the precipitate is allowed to settle to the bottom of the
tank (this may take several hours) after which the sludge is drawn,
off.
4 . 1 . 1.
L im esod a ash treatment
Studies on the removal of radioactive contamination by standard
water-treatment procedures have shown that an appreciable removal
of polyvalent cations can be achieved by the lime-soda ash-softening
process. Lime (calcium hydroxide) and soda ash (sodium carbonate)
removals reported for a variety of radionuclides are summarized in
Table IV. These data show that reasonable amounts of chemical will
provide a 90% or better removal of soluble barium, lanthanum,
strontium, cadmium, scandium, yttrium and zirconium-niobium, but
that much larger quantities of chemical were ineffective for the re
moval of caesium -barium and tungsten. It will also be noted that
lime alone was effective for the removal of 95Z r~ 95Nb. Lime and
soda-ash softening has also been tested for the rem oval of iodine,
but the results have been negative.
Treatment with lime and soda ash finds its greatest use in the
removal of strontium. In this process, hydroxides and basic ca r
bonates of the heavy metals are precipitated, while strontium
carbonate is precipitated together with calcium carbonate in mixed
crystals, the efficiency of removal of strontium being directly pro
portional to the degree of softening. Therefore, for the effective
rem oval of strontium, it is imperative that the calcium hardness
be reduced to a very low value. Such a requirement suggests a con
siderable excess of soda ash in the water during treatment and an
initial reduction of calcium hardness to a low value. Repeated ad
ditions and precipitations of small quantities of calcium could then
be used to reduce the radioactive strontium to a very low amount.
Studies have shown that an excess dosage of lime and soda ash
is in fact instrumental in removing greater quantities of strontium.
Thus the amount of material added is theoretically sufficient tosatis-
40
TABLE IV
APPROXIMATE MINIMUM COMBINED DOSAGE OF LIME AND SODA
ASH TO GIVE STATED REMOVAL*
Chemical dosage (grains/gal)** for stated removal
Nuclide
50%
75%
90%
95%
99%
Lime Soda
Lime Soda
Lime Soda
Lime Soda
Lime Soda
i4oBa - ‘«L a
2
2
4
»9Sr
2
6
4
4
3
5
5
7
9
20
20
115Cd
2
2
3
3
4
4
4
4
46Sc
3
3
3
3
5
5
91Y
2
2
4
4
6
6
12
6
2
0
5
0
12
0
17
0
48
48
48
48
95Zr - 95Nb
i37Cs 185W
137 mga
6
4
22
0
* Minimum combined dosage is defined such that, o f the variable dosages studied, the number
o f grains per gallon o f lime plus the grains per gallon o f soda ash is a minimum.
* * 1 grain/gal = 17.1 m g/litre.
fy the stoichiom etric requirements of the raw wastes and also to
provide a pre-established excess of lime and soda ash in the system.
The amount of lime feed is based upon the consumption of this chemi
cal by carbon dioxide, calcium hardness, and magnesium hardness
in the waste, and the excess to be introduced. Sufficient soda ash
is added to combine with the non-carbonate hardness and the excess
lim e. The effect of excess dosages in the range of 20 to 300 mg/1
of lime and soda ash are shown in Table V.
The use of an illite clay in the amounts of 30 mg/1 in conjunction
with the lime-soda ash process has been shown to increase caesium
removals from about 16% to approximately 55%.
4.1.2.
Aluminium and ferric hydroxide coagulation
Another standard method of water treatment consists in adding
filter alum (aluminium sulphate) or ferric salts and raising the pH
41
TABLE V
RESULTS OF LIME-SODA ASH TREATMENT FOR
REMOVAL OF STRONTIUM
Treatment
Removal o f activity
(% )'
Stoichiometric amounts
75.0
20 ppm excess lim e- soda ash
77.0
50 ppm excess lim e-soda ash
80.1
85.3
97.3
99.4
99.7
of the solution until aluminium or ferric hydroxide is precipitated;
in some cases a mixed floe is formed. Increasing alkalinity causes
the precipitation of heavy metals as hydroxides, while the bulky floe
acts as an efficient scavenger by absorbing or co-precipitating with
the other hydroxides. In some cases it may not be necessary to add
ca rrier aluminium or iron, but in most low -level wastes the p re cipitable salt content is low, and floe-forming chemicals are neces
sary. Dosages in the range of 10 to 200 mg/1 are currently used.
Such a process will in general remove efficiently all cations other
than those of the alkali metals and alkaline earths. It will have little
effect on anions, since the hydroxide floe is negatively charged.
It has been shown that in the treatment of mixed fission product
solutions alum-sodium carbonate floes are superior to alum-sodium
hydroxide floes, since in the former case strontium is also removed
as carbonate; iron floes are slightly superior to aluminium floes,
and may be operated at much higher pH with a consequent improve
ment in removal. Iodine removal could be improved by introducing
into the floe suitable absorbants or specific precipitants such as ac
tivated carbon, copper sulphate, or silver nitrate; these produce
up to fivefold increase in rem oval on alum floes. The results of
work on the removal by hydroxide floes are summarized in Table VI.
Hydroxide floes are highly efficient in removing alpha emitters
from low-activity wastes. Plutonium is removed readily on alum
42
TABLE VI
REMOVAL OF ACTIVITY ON HYDROXIDE FLOCS
Sr
m
Alum-NaOH
0.
A lum -N ^C O j
6
F eC l-N a Co
2
3
Y
Removal
Floe
Element
2
3
Alum-NaOH
Alum-Na2C 0 3
F eC l-N a C O
3
Ce
I
2
3
35
96
9
Alum-NaOH
89
Alum-Na2C 0 3
94
FeCl3-N a2C 03
95-6
Alum-NaOH
15
Alum-Na2COs
25
or iron floe, preferably the latter at pH 10; colloidal plutonium
hydroxides are efficiently removed at pH 10.3. Lime, sodiumhydroxide, or ammonium hydroxide all give good removals, but the best
floe is obtained by using lim e for neutralization. In the presence
of citrates and other complexing agents, which may be present in
waste from alpha laboratories, decontamination centres, e tc ., a
higher pH must be used to obtain both good removal and a satisfac
tory floe, the two factors running in parallel. At pH 12.0 up to
400 ppm citrate may be tolerated; higher alkalinity is also n eces
sary in the presence of complexing agents for removal on phosphate
floes.
4. 1. 3.
Phosphate coagulation
Since the heavy metal phosphates are less soluble than the
hydroxides a better removal would be expected on alkaline phosphate
floes; since strontium phosphate is not soluble a considerably greater
o v er-a ll rem oval of this nuclide should be expected. If the waste
water is a hard one, the addition of phosphates followed by alkali to
43
pH 10 will precipitate basic calcium phosphate, which forms a good
floe and acts as a carrier for the precipitated activity; in the case of
soft or de-mineralized water it is necessary to add calcium as well
as the other reagents.
Studies of the rem oval of strontium upon a calcium phosphate
floe have shown that the degree of removal depends upon the pH and
upon the ratio of sodium phosphate to calcium hydroxide. As these
two parameters are increased the efficiency increases, steeply at
first but later reaching a steady value; optimum conditions are given
by a pH of 1 1 .0 -1 1 .5 and a ratio of 2. 2 by weight of sodium phos
phate to calcium, hydroxide, corresponding to 46% excess sodium
phosphate. The excess phosphate may be removed by adding ferric
ions to give a mixed floe of basic calcium and ferric phosphates which
possesses better settling properties than a calcium phosphate floe
alone; a cheaper alternative is to use ferrous salts, but although
rem ovals are good the quality of the floe is not always as good.
The attainment of a pH greater than 11 is difficult using lime
alone, and the large amounts of calcium thus introduced would ad
versely effect strontium removals unless large amounts of phosphate
were used; it is customary instead to use calcium chloride or cal
cium hydroxide and sodium hydroxide, trisodium phosphate and ferric
ion being added after adjusting the pH.
One laboratory has found that for their wastes optimum con
ditions involve a concentration of 50 ppm of calcium, 80 ppm of phos
phate, and 40 ppm of Fe+3 at a pH of 11. 5. As shown in Table VII,
most of the polyvalent elements are removed with up to 99% efficien
cy, and removals in excess of 90% may be achieved for mixed fission
products. Little removal of the anionic activity is obtained but
strontium removal is good. Removal of ruthenium is variable,
depending upon the chemical state of the element. As in the case of
hydroxide floes, removal of alpha emitters, most of which are heavy
metals, is very efficient, figures of greater than 99% being obtained.
4. 1. 4.
Ferrocyanide precipitation
None of the methods outlined above are very effective for r e
moving caesium from waste solutions, the maximum removals re
ported being in the range of up to 30%. Investigations have shown
that precipitation of certain metal ferrocyanides is quite effective
for scavenging caesium and other isotopes under a variety of con
ditions. These techniques involve the reaction of a metal salt, com -
44
TABLE VII
REMOVAL OF ACTIVITY ON PHOSPHATE FLOCS
Nuclide
Conditions
Removal
Remarks
(%)
97.8
Calcium phosphate floe,
89Sr
excess Na3P04
91y
99.9
excess KH.PO.
Z 4
144ce
99.9
124Sb
Jar tests with
settling
excess Na3P04
67.4
excess Na„PO,
3 4
185W (anionic)
10.7
excess KH PC)
2 4
90Sr
Cs
0
phosphate floe, pH 11.5;
Sr-
92.6
50 ppm C a 2+, 40 ppm
Ce-
95.6
FeHI, 80 ppm PO^'
Ru-
47.2*
Calcium phosphate- ferric
137Cs
V
%
2 Mixed
i44Ce aa solution
0
106Ru g
95Zr
Zr- >99
Overall removal
Flow system in
sludge blanket
precipitator
93- 94+
96-97+
* Ru removal is dependent upon the chem ical state o f the element.
+ After settling.
+ Centrifuged.
monly the sulphate, with potassium ferrocyanide at the proper pH to
form the precipitate.
Ferrous ferrocyanide will scavenge caesium, ruthenium and
other nuclides at pH's in the range of 4 to 9. Beyond a pH of 9, fer
ric hydroxide begins to form while at low pH Prussian blue (ferric
ferrocyanide) is produced. The addition of a reducing agent such
as sodium bisulphate tends to speed the reaction and keep the iron
in the ferrous form . Removals of 98% of the activity from waste
liquids have been achieved using 400 to 600 ppm of ferrous fe r r o
cyanide, as shown in Table VIII.
45
TABLE VIII
RADIOCHEMICAL ANALYSES OF WASTE TREATED WITH
FERROUS FERROCYANIDE AS A FUNCTION OF TIME OF STANDING
IN CONTACT WITH THE PRECIPITATE AT DIFFERENT pH VALUES
Original untreated waste
pH
Supernatant after treatment
8.3
4 .0
5.8
8.9
8.9
5
8
Tim e the precipitate stood in contact
with solution (days)
8
15
Ruthenium (counts/m in ml)
6075
356
1300
823
327
Antimony (counts/m in ml)
1620
105
310
548
404
Zirconium (counts/m in ml)
1070
55
150
61
38
Rare earths (counts/m in ml)
10860
35
320
810
151
Tellurium (counts/m in ml)
1620
31
65
84
35
Caesium (counts/m in m l)
1080
3
8
0
1
Per cent solids
13.4
Copper, iron, cobalt and particularly nickel ferrocyanide have
been found very effective for removing caesium from waste solutions
containing high concentrations of sodium ions, D F 's of 103 having
been obtained in the presence of sodium concentrations as high as
5 N. These metal ferrocyanides are also capable of yielding caesium
D F 's of several hundred to a thousand when precipitated in wastes
at acidities ranging from 2. 5 M to pH 6. Above pH 6, ferric ferro
cyanide loses its effectiveness for caesium, as does the copper form
at a pH above 8. Cobalt and nickel ferrocyanides are effective up
to pH 10.
Studies on the effect of concentration of nickel sulphate and pot
assium ferrocyanide have shown that equal concentrations of these
reagents in the range of 0. 002 to 0. 01 M give essentially the same
caesium decontamination. The order of addition of these reagents is
unimportant when treating acid wastes, but in alkaline solutions the
ferrocyanide should be present when nickel sulphate is added to pre
vent the formation of nickel hydroxide.
46
Recent work has shown that by combining phosphate treatment
with a copper ferrocyanide precipitation, improved decontamination
of radiocaesium is possible without seriously reducing the removal
of other radioactive isotopes. The procedure is as follow s: The
pH is raised to 10. 0, using spdium hydroxide solution, after adding
the following chem ical doses:; 15 mg/1 Cu‘2+, 40 mg/1 Fe (CN6)4-,
16 mg/1 Fe2+, 80 m g /’l PO^' , and 50 mg/1 Ca2+. Calcium is only
added if less than 50 m g/l is present in the raw effluent and the PC>4 3dose must be sufficient to ensure no Ca2+ residual in the treated
effluent. Under these conditions radiocaesium removal in the range
of 98% is attained.
4. 1. 5.
Strontium phosphate precipitation
Addition of stable strontium nitrate and subsequent precipitation
of strontium phosphate has proved to be an attractive method of re
moving radiostrontium. A com parison of the effectiveness of
strontium and calcium phosphate for this purpose is shown in
Table IX. In each case precipitation was carried out at pH 9. 5 in
the presence of 0. 005 M potassium ferrocyanide and nickel sulphate,
which were added to' rem ove caesium . The calcium of strontium
nitrates were added after neutralization. At equal concentrations,
strontium phosphate is a m ore efficient precipitant than calcium
phosphate. . In fact, better decontamination of radiostrontium is ob
tained with 0. 004 M strontium nitrate than with the highest concen
tration of calciurr} nitrate as shown in Table IX. The low er con
centration of strontium nitrate required is advantageous for keeping
sludge volumes small. Results show thaf strontium nitrate is most
effective when added before neutraliza.tion. Decontamination fac
tors of around 10 to 100 have been obtained.by adding strontium ni
trate to a concentration of 0. 004 M to the acidic waste and then neu
tralizing to pH 9. 7.
'
The .precipitation of radiostrontium is enhanced by high pH.
Strontium phosphate, although less, sensitive to pH control than cal
cium phosphate, nevertheless rapidly loses its efficiency for radiostrontium removal below pH 8.5. '.
4. 1. 6. .Massive chemical treatment.
. Where.a variety of radionuclides are, or may be, in the waste,
and relatively small volumes of liquid are to be treated, a '-univer-
47
TABLE IX
COMPARISON OF CALCIUM AND STRONTIUM PHOSPHATE
PRECIPITATION OF- RADIOSTRONTIUM
Procedure: A cidic waste made 0.005 M in potassium ferrocyanide.
Solution adjusted to pH 9.5 and made 0.005 M in nickel sulphate.
Calcium or strontium nitrate added to indicated concentration.
Slurry stirred one hour at 25°C.
Concentration o f
Ca(N03)2 or Sr(N03)2
Final radiostrontium concentration
in supernatant liquid, pC i/m l*
M
C a(N 03)2 added
Sr(N03)2 added
0.004
1.18
0.32
0.008
0.71
0.10
0.015
0 .86
0.17
0.030
0.73
0.12
0.0 3 5'
0.60
0.16
* Original radiostrontium concentration = ~ 2 jiC i/m l.
sal" precipitation process may be used which will simultaneously
remove a large number of nuclides of various groups.
Recent studies have resulted in the development of dosage fo r
mulas which will, in a single precipitation, remove strontium, ru
thenium, caesium, iodine, m ercury, cobalt, iron, cerium , lan
thanum, chromium, phosphorus and rare earths from liquid wastes.
Two mixtures of precipitants, shown in Table X, have been found
effective; the formulas differ in that procedure number 2 utilizes
Bi+3 instead of the Fe+3 used in procedure number 1. Procedure
number 2 is slightly more expensive on account of the bismuth salt,
but the precipitate is deposited m ore rapidly and form s a sm aller
volume of sludge which is important in practice.
Both formulas are equally effective with regard to decontamin
ation, the D F 's ranging between 20 and 500 depending on the con
centration of chemical and radiochemical constituents in the waste.
Experience has shown that the quantities given in Table X are
suitable for low-salt-content liquids. Where wastes are encountered
which have high salt and organic or mineral acid contents, or which
48
TABLE X
TWO PRECIPITANT MIXTURES
Precipitant formula 1
Precipitant formula 2
Add to 1 m 3 o f liquid waste:
1 litre carrier solution containing 0.5%
each o f Sr, Ru, Ce, and Zr chloride
(g)
35
Antifoam agent
w
150
K4Fe(CN)6 -3H 20
250
NiS04 • 6H20
(g)
Antifoam agent
10
KI
50
NaHS03 • 7H 20
30
AgN03
50
NaHSO -1 H O
5
2
150
K4Fe(CN)6.3 H 20
10
KI
250
NiS04 • 6H ,0
30
AgNOj
250
250
FeCl3
50
250
Ca(OH)2 tech.
Bi(N03 ) 3
Ca(OH)2 tech.
NaOH to pH 10.5
NaOH to pH 10.5
contain detergents, considerably larger quantities of precipitation
chemicals must be used.
4. 1. 7.
Treatment of sludges
All the processes discussed above produce sludges as a result
of the reactions taking place during chemical treatment. Slud.ge
volumes vary according to the process used, phosphate and lim esoda methods producing the largest quantities, particularly where
a hard water is being treated. The volume of the wet sludge will
also depend on the dosage of chemicals used, and the nature of the
precipitated solids.
The water content of these sludges is usually high, solids con
tents of less than 5% resulting from normal settling techniques. Fur
ther treatment of the sludge depends upon the method of disposal
employed. If only short or medium-lived nuclides are involved, the
sludge may be stored in tanks to permit decay. Extended storage
49
will also result in some thickening of the sludge and consequent vo
lume reduction. In all cases it is desirable to reduce sludge volumes
to a minimum and various de-watering processes may be used, such
as filtration, centrifugation, or a freeze-thaw step followed by fil
tration. By these means the solids content of the sludge can be in
creased from an initial 1 to 3% to a final content in the range of 30
to 50%. The freezing and thawing.treatment gives rise to a granular
material which settles and filters well. In this process the sludge
must be frozen slowly and completely and, while the rate of thawing
is unimportant, filtration should take place as soon as possible after
thawing.
Vermiculate or other absorbent materials should be added to dry
out de-watered sludge before seating it in metal drums for storage
or disposal. If dilute sludges are to be packaged for disposal without
further treatment, they can be solidified by mixing with cement or
a blend of cement and verm iculite, again using steel drums as the
final disposal container.
4 .2 .
ION EXCHANGE USING ORGANIC RESINS
4. 2 . 1.
,
Treatment by ion exchange
One of the simplest methods of decontaminating a waste solution
is to mix it in batches with an ion-exchange resin; the contaminants
are concentrated on the exchanger. Removal of over 99% of most
long-lived fission products have been achieved in this manner by
using 2700 ppm of a mixed anion and cation exchange resin. How
ever, more efficient use of the exchanger may be achieved by pas
sing the waste down a column packed with the resin. Since most of
the radioactive species, are cationic, decontamination of the wastes
resem bles .water softening by a cation exchanger on the hydrogenor sodiumrcycle. On passing a waste of constant composition down
a column of cation exchanger the order in which the inactive cationic
species appear, in the effluent frona the column, is determined, by the
relative affinity of the exchanger for all the cationic sp.ecies, .in
cluding that originally, present on the resin. On parsing.hard water
through a. column of resin in a sodium form, calcium and magnesium
are removed from solution and the water is thus softened. When the
resin is saturated with the total hardness cations, these appear in
the effluent causing the breakthrough of hardness.
50
The use of ion-exchange resins may be of considerable value to
industrial laboratories and hospitals for the removal of radioactivity
from aqueous wastes having a total solids content of less than
2500 ppm, preferably below 1000 ppm. The principles governing
the rem oval of radioactive ions by ion exchange are not different
from those of sim ilar chem ical elements. However, in a waste,
particularly one composited from many laboratory operations, the
radioactive elements are in tracer quantities with respect to inactive
ions.
The wastes which are amenable to treatment by ion exchange
are of two varieties - those from general laboratory operations and
those from laboratories where only one tracer is used. In the first
group the wastes may contain any or all types of radioactivity to
gether with acids, bases and salts and the composition both chemic
ally and radiochemically will be unknown. To analyse for all con
stituents would be not only difficult but too time-consuming to be eco
nomically feasible. Under these circumstances an analysis is made
for pH, approximate total solids, and for total alpha and beta-gamma
activity. An approximate total solids content may be obtained quick
ly by simply weighing a planchet before adding a known volume of the
liquid for counting and then reweighing the planchet after the sample
has been evaporated. The difference in weight in milligrams divided
by the volume of the sample in' m illilitres gives the milligrams per
m illilitre. This result multiplied by 1000 gives the parts per million.
This result may be an error as much as 10-20%, but it is sufficient
for an estim ate'of the amount of total solids present. If the total
solids content is less than 2500 ppm, ion exchange may be used.
However, for most efficient use total solids should be less than
1000 ppm and for general laboratory wastes this is usually the case-.
Although many cation exchange resins are available on the
market, those of the polystyrene divinylbenzene sulphonic acid type
(Dowex 50, Nalcite HCR) have been found most satisfactory for good
removal of radioactivity.
The flow -rate recommended by the manufacturers for highcapacity cation resins of the divinylbenzene sulphonic acid type is
270 litre/m in m3 of resin. However, it has been shown that for the
removal of gross fission products from radioactive waste solutions
there was very little difference in the removal of radioactivity when
using a flow-rate ranging from 270 to, 1350 1/min m3.
For the best over-all removal of gross fission products pH 2. 5
is recommended. A comparison of the removals obtained from total
51
beta-gamma radioactivity at various pH's is shown in Table XI.
These data show a high through-put capacity and a greater removal
at pH 2.5 for the ion-exchange column alone. Although a better
over-all removal of activity occurred at pH 9. 5, half this removal
was obtained by filtration before hardness breakthrough and over
twice as much by filtration after hardness breakthrough.
The reasons for these results are apparent when one considers
the chemistry of the fission products. With the exception of z ir
conium and niobium all the fission products should be ionized at pH
2.5. The poor results particularly at pH 5. 5 may be due to the for
mation of radiocolloids of some of the other fission products. At
pH 9. 5-there will be formation of the hydroxides of the rare earths
and of radiostrontium.
The regeneration of resins presents some difficulty because
radioactive contaminants, particularly those present as colloids, are
not always removed as easily as are the inactive species. Further
more, another liquid waste is produced as a result of regeneration
which must be treated and disposed. Accordingly, disposal of the
resin following exhaustion is recommended for sm all-scale appli
cation.
The results experienced in the treatment of laboratory wastes
over a period of several months by ion exchange on a divinylbenzene
sulphonic acid type resin is given in Table XII. The wastes were fil
tered before passage through the ion-exchange column. These wastes
may have contained various ions; complexing agents such as oxalic
and citric acids, and minute amounts of organic solvents, as well
as some soap and detergents.
4. 2. 2.
A.
Cation exchanger for processing general laboratory wastes
Size
The size of a cation exchanger will depend on the total hardness
of the waste, the species and level of radioactivity to be removed,
the perm issible level for discharge, and the volume.
(a)
F or illustration, suppose the total hardness of the waste
averaged 170 ppm as CaC03 (the maximum was 1700 ppm). The
activity to be removed was mixed fission products averaging
1 .6 X 10"4 juCi/ml (maximum 4X 10-4 /uCi/ml), and the tolerance
level for discharge was 4X 10“5 (LiCi/ml. The waste was to be di
luted with non-radioactive wastes before final discharge, and the
volume was 4000 litr e s /d .
52
TABLE XI
EFFE CT OF pH AND FILTRATION ON REMOVAL OF RADIOACTIVITY BY CATION EXCHANGE
Feed
F ilter
pH
elem en t
1 .8
2 .5
2 .5
none
none
yes
4 .0
none
5 .5
none
8 .0
A V olum e
A verage 0- y a ctiv ity ,
( c p m /m l)
throughput
Bed volum es
Feed
Filtrate
Final
efflu en t
Integrated d econtam ination factors
Filter
800
1260
_
137
3400
978
...
197
...
_
85
Ion
exchange
9 .2 Ha
5 .0
850
1180
2020
942
...
179
...
...
...
...
83
...
169
...
...
...
...
1 0 .5
2 .8
514
...
...
815
1180
1960
950
655
1280
2900
1088
680
1200
2050
1160
...
...
122
...
...
426
291
1 4 .1 Ha
5 .2
3 .7
O ve r -a ll
...
...
...
...
1 4 .2 Ha
5 .6
...
...
5 .0
...
...
8 .0
none
815
1300
...
262
...
5 .0
...
8 .0
yes
815
1390
233
1120
1170
...
...
...
...
...
...
2 .9
1320
830
493
256
1 .7
1 .9
790
920
308
49
3 .0
6 .3
1 8 .6 Ha
175
4990
569
274
8 .7
2 .1
1 8 .2
670
880
289
268
3.0
1 .1
3.3
9 .5
Feed:
C olum n:
yes
408
T ap water (8 5 ppm total hardness as CaCC^) adjusted to pH shown and 1 to 2 - y r-o ld m ix ed -fission products added.
1 .6 cm x 60 cm Pyrex glass tube, containing 50 m l N a lcite HCR-Na form .
Flow-rate:
a H = Hardness breakthrough.
270 1 /m in m s
6 .0 Ha
3 .3
Cn
►
fc.
TABLE XII
ANALYSIS OF RETENTION TANK WASTES AND CATION EXCHANGE EFFLUENT
Filtered Feed-Analysis
Batch v olu m e
PH
( litres)
2 .3
0
2 .5
22
.
5000
2 .7
26
3800
3 .2
111
3000
4 .4 a
21
5000
3. l a
102
5800
7 .4 a
102 ,
,
8 a ctiv ity
solids
(/jC i/m l)
(p p m )b
(p pm )
3500
3800
T otal
Hardness
as CaCOs
;
Effluent
6 a ctiv ity
R em oval
DF
(%)
(fiC i/m l)
41
2420 '
2 .4 X 1 0 " 4
5 .9 x 1 0 '6
98
1660
1 .6 x 1 0 "4
4 .0 x 1 0 '5
75
4 .0
2120
9 .9 x 10’ 5
1 .5 x 1 0 '5
85
6 .7
1100
1 .4 x 1 0 '4
6 .3 x 10"5
54
2 .2
1 .6 x 1 0 " 4
8 .8 x 10*6
94
1 7 .8
1000
8 .2 -* 1 0 '5
2 .1 x 1 0 '5
74
3 .5
860
2 .4 x l O ' 4
3 .6 x TO"5
85
6 .6
7 .9 x 1 0 ' 5
62
2 .6
880 1
4550
• 2 .3
144
1000 . -
2 .1 x 10" 4
4250
1 .9
111
3680
2 .5 x 1 0 - 4
2 .1 x l O '4
17
1 .2
3500
2 .1
150
1610
1 .2 x 1 0 -4
3 .8 x 1 0 - 5
69
3 .3
4500
2 .3
141
1070
9 .8 x 10" 5
7 .8 x lO -5
21
1 .3
5400
2 .8
131 -
1125
9 .3 x 1 0 " 5
4 .3 x 10" 5
4100
150c .
2090
4100
1 .9 *
1 .9 s
150c
6500
3 .2 a
148
4350
3 .6
195
3 .0
106
;
'
.
2 .2
54
1 .1 x 10‘ 4
2 .6 x 10‘ 5
77
4 .3
9 .4 x 1 0 " 5
2 .1 x 10" 5
78
4 .6
1020
2 .4 x 1 0 - 4
5 .4
3 .6 x 10" 4
4 .3 x 10“ 5
4 .8 x 1 0 ' 5
82
1240
87
7 .7
1550
1 .7 x 1 0 '4
4 .8 x 10" 5
72
1860
.
71150
A verage
F ilter:
A lsop, 30 cm d ia m . paper N o. 40.
Resin C olum n:
30 cm d ia m . contain ing 0 .1 m 3 N alcite HCR-Na form .
Flow rate =
270 1 /m in m 3
apH adjusted to ~ 2 . 5 before' filtration.
b pianchet m ethod ± lOô.
E s tim a te d hardness.
'
3 .6
The average decontam ination fa ctor fo r the above w ill be:
1.6X 10-4 juCi/ml
4X10-5 MCi/ml
The maximum total hardness as CaCC>3 is 1. 7 g /litr e , and if the
capacity of the cation resin used is 68 700 g of CaCC>3 per m3, this
will be equivalent to:
68 700 g /m 3
- —y g /lit re" ~
/ 3
litres/m .
Since the volume to be treated per day was- 4000 litres:
4000 litres
- .
3
40 000 litr e s /m 3
• m •
However, on the basis that a decontamination factor of 4 is sufficient
and the average hardness is 170 ppm as CaCC>3, a cation exchanger
could be used for about the equivalent of 4X 107 litr e s /m 3 before
the resin must be replaced.
If a 0. l~m 3 bed were used, 4X 106 litres could be processed
or the exchanger could be used for 4X 1 0 6 /4 X 103 = 1000 d or 3 yr
before needing to be discarded.
There are two things to be particularly noted in the above cal
culations: capacity for hardness breakthrough was based on maxi
mum hardness in waste whereas capacity for activity removal was
based on the average figure. In the above example a 30-litre ex
changer could be installed as it would be sufficient for a year's usebefore having to be discarded.
(b)
Suppose, however, that all the above data for the wastes
were the same but it was required to remove strontium-90 to below
its maximum permissible level, namely 8 X 10_7juCi/ml.
The maximum activity will not have to be taken into consider
ation (in the above example, 4 X 10-4 /uCi/ml), but rather the
strontium-90 content of the feed must be considered. Let us also
assume, based on previous analyses of these wastes for strontium-90,
that it is safe to consider that 10% of this w ill be strontium -90.
55
Therefore, the level of activity to be considered as feed is
4X 10"5 juCi/ml and a decontamination factor of only 50 would be re
quired.
4 X 1 0~5 juCi/ml
8 X 10"7 /uCi/ml
From Table XIII it is seen that at pH 2. 5 it is possible to remove
strontium-90 from tap water containing 85 ppm hardness as CaC0 3
with a decontamination factor of 1 X 105 if not m ore than 615 bed
volumes of water are treated. But in the example given above the
maximum hardness was 1700 ppm or 20 times greater than 85 ppm.
However, a decontamination factor of only 50 will be required. Re
ferring to the same Table, it is noted that about 1400 bed volumes
of 85-ppm hardness water may be processed before the DF is re
duced to 50. Therefore, if the water in the example is 20 times
harder than the tap water in the data of Table XIII it might only be
possible to process 70 bed volumes of waste before reaching the
maximum perm issible level for strontium-90. If the volume to be
treated per day was 4000 litres it would require about 60 litres
of resin. Therefore, a cation exchanger containing 60 litres of resin
will be required for each day's run and, under these conditions, ion
exchange would be practical only if the resin were regenerated.
B.
Equipment and m aterials of construction
Since the wastes being processed will be on the acid side, pH
2.5, a plastic or rubber-lined vessel and either stainless-steel pipe
and valves, plastic lined steel, or plastic pipe will be required.
The vessel may be any standard ion-exchange unit. A glass,
saran, or stainless-steel screen, instead of gravel and sand, is
preferable for holding up the resin particles, since the gravel and
sand becom e radioactive and must be disposed of as solid waste.
C.
P rocess design
In the example given above, where regeneration is not con
templated, the only equipment required is a conductivity meter, a
flow meter, ion-exchange unit and holding tank. The latter is used
as it is necessary to get a sample of the composite effluent to deter
mine the activity before discharge. A diagram of such a system is
shown in Figure 18.
56
TABLE X m
R E M O V A L O F S T R O N T I U M -90 B Y C A T IO N E X C H A N G E
90 Sr from M ix e d fission
90Sr f r o m M Sr tra cer
(c p m /m l)
pH 2 . 5
pH 5 . 5
-----
-----
---
1 .4 X 105
1 .3 X 105
375
co
320
0 .8 7
4 . 3a
1 .6 x 106
3 .0 X 1 0 4
2 . 1 X 10*
pH 2 . 5
pH 5 . 5
16
15
16
40
0 .2 7
0 .0 4
0 .0 5
59
pH 2 . 5
pH 7 . 0
---
---
20 0
0 .0 5
0 .0
0 .0 5
320
320
0 .0 7
6 .1
2 .0 X 106
0 .0 8
0 .0
0 .1 9
200
<o
84
0 .2 4
0 .5 3
5 .8 X 106
61 5
0 .2 7
0 .3 0
0 .2 2
59
50
73
1 .3 a
2 .4
1 .1 x 105
5 .4 X 1 0 *
820
0 .4 3
0 .4 5
0 .0 7
37
33
229
20
7 . 0 X 10*
3 .1 X 10s
1000
0 .1 1
0 .9 7
0 .3 1
145
15
52
145
1 32 0
1 63 0
1 .8 a
0 .5 5
2. 0a
0 .5 6
1 .4 a
27
29
1 .3
1 92 0
3 .5
1 .4
1 .3
1 2 .3
8 .9
7 .5
1 1 .4
665
3 . 9 X 10 s
4 .6
1 0 .7
1 2 .3
1 . 1 x 10 4
F eed:
T a p w a te f co n ta in in g 85 p pm to ta l hardness as C a C O j .
1 . 6 - c r o .- d i a m . P yrex g la ss co n ta in in g 50 m l N a l c it e H C R -N a f o r m .
pH a n d a c t i v i t y a d d e d as s h ow n .
F lo w ra te :
27 0 1 /m in m 3
a M a x im u m p e r m is s ib le le v e l e x c e e d e d at this p o in t, s in c e 0 . 7 c p m / m l = 8 x 1 0 ” 7 j i C i / m l fo r instrum ent u s e d .
Ui
-n]
pH 2 . 5
400
C o lu m n :
b
pH 7 . 0
pH 1 . 8
pH l . J
0
D e c o n t a m in a t io n
factor*5
In e fflu e n ts
( c p m /m l)
D e c o n t a m in a t io n Factor**
p rod u cts In e fflu en ts
V o lu m e
th ro u gh - put
( b e d v o lu m e s )
. . . .
D e c o n t a m in a t io n fa c to r
a c t iv it y in fe e d '
-------- r r r — :------ t t
a c t iv it y in e f f .
•
42
49
300
3 . 3 x 10 S
8 . 6 x 10*
966
210
36
1 2 .7
2 .5 X 10s
2 . 7 X 10*
433
39
15
AIR VENT
BACKWASH AND
SPENT REGENERANTS
TO SEPARATE
HOLDING TANK
HARDNESS-FREE WATER
FOR RINSING AND BACKWASHING
FILTERED FEED
FIG. 18.
D.
C ation ex changer - sch em a tic
1.
Pump to supply a ctiv e feed
7.
C on d u ctivity m eter
2.
Pump to supply nitric a cid
8.
C on d u ctivity ce lls
3.
Pump to backwash colu m n
9.
Sam pling point for effluent
4.
Flow in dicator for side stream
5.
Flow m eter for n itric a cid and rinse w ater
con ta in in g 0.1 m 3 cation resin.
6.
Flow m eter for a ctiv e feed
S teel shell with Koroseal lining
10.
Tank 150 c m high by 35 cm I. D. ,
Operation
Any ion-exchange resin must be first conditioned by exhausting
and regenerating it at least twice. This is usually done by simply
passing hard water through the bed until it is' exhausted and then re
generating it with acid if the hydrogen form of the resin is desired.
The gross beta activity and approximate total solids of the feed
are determined. If the latter is above 3000 ppm it is not practical
to process by ion exchange. If the total solids are below 3000 ppm
then the pH of the feed is determined and it is adjusted to pH 2. 5
with acid or alkali. If perm issible discharge level is based on
strontium-90, the amount of this radioactive element in the feed must
be determined.
58
The feed is then filtered and pumped to the ion-exchange column
at the rate of 270 to 1350 litres/m in m3 . Two conductivity cells are
installed, one in the effluent line and the other in a line-bleeding
feed just before it has passed completely through the resin; this is
in' order to get the hardness breakthrough point at the instant of
initial breakthrough of calcium and magnesium. An effluent samp
ling point is required in order to check for activity from time
to time.
4 .3 .
EVAPORATION
While evaporation is the most effective means decontaminating
liquid radioactive wastes, the use of this p rocess has in the past
been confined to large treatment centres on installations because of
the high capital, and operating expenses involved.
Recently, however, several packaged units have become com
m ercially available which are intended for treatment of relatively
small batches of low“ level liquid wastes, and which therefore might
be of interest to small installations which generate waste requiring
DF's of from 104 to 106 before discharge. Two of these units are
described below.
4. 3. 1.
Low-temperature evaporator
The- first system, a flowsheet for which is shown in Fig. 19,
concentrates radioactive liquid waste by using a low-tempera.ture
high-vacuum evaporation process. When the desired concentration
is achieved, residual wastes are then transferred to storage or to
a solidification system for ultimate disposal.
On the average, the radioactivity of the input wastes has been
reduced from approximately 10-2 to 10-4 p C i/cm 3 to the order of
10-8 to 10-9 juCi/cm3 in the distillate.
The principal features of the process are:
(1) Low temperature operation
(2) Efficient multiple system of separators
(3) Automatic purity sensing system
(4) Automatic self-cleaning during shutdown.
During operation, the hot-waste batch tank (1500-litre capacity
on the 190-litres/h unit) is filled with raw waste from the facility
w aste-collection system. Once the raw waste is in the batch tank
59
w
m
s
§
LEGEND
PUMP
EDUCTOR
GLOBE VALVE
P UR ITY SENS1N6 ELEM ENT
BATE VALVE (N O RM ALLY CLOSED]
LIQUID LEVEL CONTROLLER & FEEDER
THR EE-W AY SOLENOID VALVE
X
GATE VALVE
FIG. 19.
#C*3 GLOBE VALVE (N O RM ALLY CLOSED)
o LOCAL M OUNTED INSTRUM ENT
© PANEL M OUNTED INSTRUMENT
©
©
©
TEM PER ATUR E INDICATOR
FLOW RATE INDICATOR
LIQUID LEVEL INDICATOR
DEN SITY INDICATOR
©
©
C O NDU CTIVITY CONTROLLER
VACUUM INDICATOR
L ow -tem pera tu re waste evap ora tion system
and the equipment started, the system operates unattended until the
cycle is completed. The batch-tank pump circulates the radioactive
liquid waste continuously through the evaporator section of the con
centrator. The waste in the evaporator section is boiled at a low
temperature and at a high vacuum until it reaches the desired con
centration. The concentrator operates at approximately 3 8 -4 4 °C
60
boiling temperature and at a vacuum of approximately 690 mm of
mercury. The rate of evaporation and distillate production is con
trolled by throttling the heating and cooling water valves.
A level controller on the evaporator maintains a constant level
of radioactive liquid waste. A portion of this waste is extracted con
tinuously by an eductor and returned to the batch tank, resulting in
an uniformly concentrated batch of raw waste. When the desired
solids concentration is achieved, the concentrated waste is trans
ferred to sludge storage, a drumming station, settling tank or other
means of disposal by the batch-tank pump. The amount of concen
tration varies with the type of waste being concentrated. This pro
cess has achieved a total solids content as high as 53% in the waste.
The density of the material being concentrated is continuously moni
tored and indicated on the control panel. The distillate cycle b e
gins by the vapour in the concentrator being condensed on the con
denser tube bundle to form the distillate. This distillate is with
drawn from the concentrator by an eductor in the distillate circulat
ing line. The distillate pump circulates distilled water from the
distillate tank through the eductor in a closed loop in the distillate
circulating line. This eductor also creates and helps maintain the
vacuum in the concentrator.
Before vapours reach the condenser section, they pass through
specially designed separators to remove droplets from the vapour,
thus increasing the decontamination efficiency of the unit by prevent
ing the carry-over of contaminated particulates.
If the purity of the distillate is not as high as desired, a con
ductivity cell (purity sensing element) in the line to the distillate tank
operates a solenoid valve which returns the distillate to the waste
cycle for reprocessing. As soon as the concentrator operation is
again stabilized and the desired purity is achieved, the valve auto
matically re-d irects the flow to the distillate tank. The distillate
pump automatically discharges the distillate as it is generated. At
the discretion of the operator, the distillate can be passed through
a mixed-bed ion-exchange column which acts as a polishing unit to
purify the water further, if desired. The final distillate is suitable
for reactor-pool make-up or other purposes requiring highly puri
fied water. Since the water from the concentrator has already been
highly purified, the de-mineralizer resins will last through thousands
of litres of distillate. The ion-exchange resins are visible, and can
be readily removed and replaced.
61
The process has been designed to be safe in operation. Since
steam is not used, a steam accident cannot occur. If leakage o c
curs, it will be into the evaporator since it is at a lower pressure
than atmospheric. A power failure will automatically shut down the
process, regardless of heat input conditions. Since hot water is
used as the heating medium, loss of power will cause the vacuum to
be lost and boiling in the evaporator will cease since it will now be
at atmospheric pressure.
A unique feature of the process is the automatic self-cleaning
action of the concentrator using a portion of the distillate from the
distillate tank when the unit is shut down. The self-cleaning occurs
when the distillate pump is de-energized, thus breaking the vacuum
in the concentrator. When the vacuum is broken, a portion of the
distillate tank water is forced back through the distillate line to the
concentrator. This distilled water spills over into the concentrator,
rinsing the separators in addition to re-submerging and cleaning the
tube bundle. This water is then withdrawn to the batch tank by the
batch-tank pump.
The system is available in various capacities, including
190 litres/h , 380 litres/h , 1150 litre s/h and larger sizes to meet
special requirements. It is shipped completely assembled on a skid,
and factory tested. Complete instrumentation is provided with the
unit. It is only necessary to connect utility services to make the
unit operational. Dimensions of the 190-litres/h unit are 2. 85 m long,
1 .2 m wide and 2 .7 m high.
Power requirements for the 190 -litres/h system are a m axi
mum of 3 kVA to operate pumps and instrumentation. Approximately
2.8 litres/m in of air are required. Temperatures and flow of hot
water can be varied to suit most optimum local conditions, ranging
between 65-80°C and 40 to 120 litres/m in for the 190-litres/h unit.
Cold water is used as the condensing medium.
4. 3. 2.
Wiped-film evaporator
The second system, a flowsheet for which is shown in Fig. 20,
is based upon the use of a steam-heated wiped-film evaporator. This
type of unit is particularly advantageous when treating wastes which
have a tendency to foam.
The operation of the system at distillation rates averaging
150 litre s /h yielded D F 's of the order of 107 when treating waste
having an initial activity level of ~ 1 0 -1 ^ C i/m l.
62
'/âdeaactcae JtifyciicL ‘TOatfe
‘p & ciiity
FEEDTANK-
FIG. 20.
Wiped-film evaporator system
In operation/, raw waste is pumped to the feed tank at a rate con
trolled by the liquid level in the residue tank. In this way evaporation
to dryness on flooding of the system is prevented.
- '
Solution flows by gravity from the feed tank to the evaporator,
where it runs down the inside of the steam-heated walls. Residue
drains from the evaporator to the residue tank, where it is recycled
through an'overflow pipe in the feed tank and mixes with fresh dilute
feed.
Specific gravity of the concentrate is measured by bubbling air
slowly into the overflow pipe, thereby measuring the hydrostatic head
in this fixed liquid leg. When the sp ecific gravity reaches a p re
determined level, concentrate flow from the residue tank is diverted
in whole or in part to a sludge receiving drum. This rem oval of
concentrate or sludge is done without interrupting the evaporation
p rocess.
Water vapour produced in the evaporator passes through two
internal separators, an external demister, and is condensed. Distil
late from the condenser flows to one of two 1200-litre distillate re
63
ceiver tanks. When one is full, flow is automatically diverted to the
other. The distillate is then pumped through one or both ion exchange columns. De-mineralized water is collected in either of
the two 1200-litre de-m ineralizer tanks, where it is monitored and,
if within specifications, discharged to the sewer.
Utility requirements include 180 kg/h or steam at 5 atm pressure
and 150 litres/m in of cooling water. The facility is mounted ona steel
base and has over-all dimensions of 4.2 m long by 3 m wide, with
a height of 3.2 m.
4 .4 .
CONCLUSIONS AND RECOMMENDATIONS
It should-be emphasized that the data reported in the previous
sections, while serving as a general guide to the characteristics of
a given process, cannot be considered as necessarily representative
of what will be obtained in practice. Many factors such as local
water quality, wast-e-water composition, radionuclide concentration
and small quantities of detergents will have a strong influence on the
decontamination factor actually achieved.
In many instances, careful attention to good segregation practice
will eliminate the need for liquid-waste treatment entirely, since
small volumes of more concentrated liquid wastes which do accumulate
can best be handled by solidification without prior treatment.
Where wastes have a low total solids content, ion-exchange
treatment is the most suitable method. It has the advantages of
simple equipment requirements, high volume reduction factors, and
the activity concentrated in a form which is easily handled for pack
aging and disposal. The main disadvantage is cost of the resins, but
unless rather large volumes of waste are involved, the costs should
not be excessive.
Where the solids content of the waste is too high to permit the
use of ion-exchange methods, and where large decontamination fac
tors are not required, chemical treatment may be useful. However,
despite the low costs associated with the treatment process itself,
volume reduction factors are often low, particularly where sludge
treatment is not practical. Consequently, considerable costs and
effort may have to be expended in the solidification and disposal of
the sludges resulting from chemical treatment.
The choice of a particular process will be governed by the nature
of the installation and operations producing the waste. For many
64
of the chemical treatment processes discussed above, a consider
able amount of laboratory work is required to determine optimum
dosages of chem icals. This may be warranted in cases where the
waste is produced on a regular basis and has a fairly uniform chemi
cal and radiochemical composition, but where the volumes are too
low to justify the installation of a chemical treatment plant. On the
other hand, if it is necessary to treat only an occasional batch of
waste which is unpredictable in its characteristics, use of the mas
sive chemical treatment process described in section 4 .1 .6 will
eliminate the need for much of the laboratory work and will probably
be more economic in the final analysis, despite the cost of chemicals
involved.
Evaporation is the method of choice where high D F's are r e
quired, or where the waste is otherwise not suited for processing
by alternate techniques. Capital costs compared to the other methods
are high, but the units described in section 3 will treat waste for a
few dollars per cubic metre including amortization if their processing
capacity-is fully utilized.
5.
5.1.
SOLID-WASTE TREATMENT AND DISPOSAL BY
INDIVIDUAL USERS OF RADIOISOTOPES
INCINERATION
5. 1. 1.
Introduction
Incineration, as a unit operation, will substantially reduce com
bustible waste volumes and as such represents a useful waste treat
ment or handling process. Where radioactive contamination is in
volved, other factors must be considered. The radioactivity, per
se, remains unaltered. Depending upon the physical and chemical
characteristics of the isotopes involved, the radioactivity may be
transferred from its original combustible carrier and pass up the
stack as a contaminated gaseous or particulate effluent; may adhere
to or "plate out" on interior surfaces of the incinerator or associated
piping; it may be retained in the ash; or it may be distributed
in various proportions in the stack effluent, on the incinerator sur
faces and in the ash.
From the foregoing, it is apparent that where incineration is
utilized as a waste-handling method, there are implicit consider
65
ations of treatment or handling of stack effluents and handling and
disposal of radioactively-contaminated ash material. Where con
ventional incinerators are involved, there generally will be little
or no provision for-treatment of stack effluents. In many cases, the
stack itself may consist essentially of a roof outlet, and the diffusion
and transport of effluent from the outlet will be dependent upon its
relationship to the building and surrounding buildings. Also, in the
case of many incinerators, the ash-handling facilities may not be
very highly developed and, in fact, may constitute the major source
of contamination to personnel. Ash-handling facilities and operations
can be modified and improved. These factors, therefore, must be
carefully considered in assessing the ability of specific installations
to handle adequately different quantities of radioactive m aterials.
5.1. 2.
Applicability
Small domestic or institutional incinerators have been found to
be very useful treating combustible low -lev el radioactive solids,
particularly putrifiable wastes such as animal carcasses, cage clean
ings and physiological and pathological remains. However, since
no special air-cleaning or ash-handling facilities are usually as
sociated with such units, activity content of the wastes must be re
stricted to levels which w ill not result in exposure of the general
population to concentrations which exceed MPCair .
The use of incineration for the treatment of wastes containing
relatively large quantities of radioisotopes requires specially de
signed or modified units utilizing elaborate air-cleaning and ashhandling systems; because of the cost and complexity involved, the
consideration of such systems by individual users is not recommended.
By segregating small volumes of highly contaminated material from
larger volumes of slightly contaminated combustibles, activity levels
in many, if not most, cases will fall within the range where use of
institutional incinerators may be permitted.
5.1. 3.
Simple approach to calculating safe limits for incineration
There are two limitations on the safe levels of activity which
may be disposed of by means of institutional incinerators; concen
tration in flue gases and concentration in ashes.
66
5. 1 . 3 . 1 .
Concentration of activity in flue gases
Assuming a relatively uniform distribution of radionuclides in
the waste material;
Let t = minutes of burning per day
A = rate of discharge of flue gas in cm 3/m in
y =/uCi of radioactive material which may be disposed of per
day.
Then the average concentration in unfiltered flue gases, assuming
complete liberation
iuCi/cm3
Assuming a dilution of 100 between stack mouth and point of breath
ing (a conservative assumption), and using 1/10 of the 168-h ICRP
occupational MPCa as the limiting factor, then
y /t A ^ X M P C a
y = 10 MPCatA
(1)
For example, if the incinerator is operated 300 min/d, the flue gas
discharge = 2X 107 cm3 /min, and it is desired to determine the quan
tity of 131I (168-h occupational MPCa = 3X 10_9/juCi/cm3) which may
be disposed of, then
y ( 131I) = 10 X 3X 10‘ 9 X 300 X 2X 107 i^Ci
= 180 juCi
Complete liberation in the flue gases need only be assumed for those
isotopes known to be volatile, such as 3H, 14C, 35 S, 74 As, 82 Br,
131I and 203Hg. In calculating flue-gas concentrations for other non
volatile isotopes it may be assumed that only 10% of the activity is
released with the flue gases, and equation (1) becomes
y = 100 MPCa tA
(la)
67
5. 1. 3. 2.
Concentration of activity in ash
When wastes contaminated with non-volatile radioisotopes are
incinerated, most of the activity will remain with the ash, and may
constitute an inhalation hazard during ash removal and subsequent
handling.
The limits on quantities of activity which may be incinerated
due to ash contamination may be computed as follow s:
Ash residue = 10% by weight of waste incinerated.
Let C =Maximum concentration of dust which may be suspended
in air = 3 X 10“7g/ cm 3 .
W= Weight in grams of waste (contaminated and non
contaminated) charged to incinerator,
y =fj,Ci of radioactive materials which may be charged to
incinerator in W grams of waste.
then
y /0 . 1 W = specific activity of ash
Again using 1/10 of the 168-h ICRP occupational MPCa as the
limiting factor,
y /0 . 1 W = 0. 1 MPCa fC
y =W MPCa/ 100C
y =W M P Q /3X lO"5
(2)
For example, if 100 kg of waste are incinerated before ash re
moval, the amounts of 32P (MPCa =2X 10"8/iC i/cm 3 ) which could be
contained in the waste before special ash handling precautions would
be required is
vf3 2 p w lO- 5--X 2 X _10-8
‘
3X 10-5
= 67 /uCi
In case of volatile isotopes, it may be assumed that only 10%
of the activity remains in the ash, and for these isotopes, equation
(2) becomes:
y =W M PCa/3X 10-6
68
(2a)
Where a combination of isotopes is involved in known amounts,
the limit for the combination should be derived by determining, for
each isotope, the ratio between the quantity present in the com
bination and the limit otherwise calculated for the specific isotope
alone using the above equations. This ratio should be expressed as
a fraction, and the sum of such fractions for all the isotopes in the
combination may not exceed 1 (unity).
Where activity levels exceed those calculated using the above
equations, special ash-handling procedures should be used. R espir
ators should be worn by those involved in ash handling, the ashes
should be moistened to inhibit spread of dust, and the ashes should
be packaged as low-level solid waste rather than disposed of via nor
mal non-active refuse-disposal procedures. Figure 21 illustrates
the removal and packaging of ashes from a small domestic incinerator.
FIG. 21.
R em oval and p a ck ag in g o f ashes from a sm a ll dom estic incinerator used for incinerating radioactive
waste
5.2.
COMPRESSION
For other than putrifiable wastes, com pression or baling r e
presents a useful method of solid-waste volume reduction, par
ticularly if incineration facilities are not already available or if ac
69
tivity levels in the waste frequently exceed those which may be safe
ly incinerated in institutional or domestic type units.
Although it may appear that incineration provides a consider
ably larger volume reduction than compression, this apparent ad
vantage may not in fact be realized when one considers that the
m ajority of low -level solid wastes which are not combustible are
com pressible. In general, compression involves lower capital in
vestment and operating costs than incineration, and is a consider
ably sim pler operation. However, it would not be worthwhile to
install compression equipment unless the facility generated at least
100 m3 of solid waste per year. These factors should be carefully
evaluated in terms of the installation's particular waste character
istics when considering the acquisition of new solid-waste treatment
facilities.
Many installations utilize conventional baling presses, suitably
enclosed in a ventilated housing to reduce the likelihood of spread
of contaminated dusts. Such units are not suitable for the com
pression of waste contaminated with alpha emitters or other highly
toxic materials.
Recently a unit designed especially for compacting contaminated
solid waste has become commercially available. The device, shown
in Fig. 22, involves a hydraulic cylinder that compacts the solids in
a standard 55-gal (208 litres) drum; with a lid in place when the drum
is full, it then serves as a shipping, storage or burjal container.
Solid waste may be loaded into the drum while it is in place within
the compaction device. To prevent the spread of radioactive dust
the compaction is accomplished within an enclosure that may, if de
sired, be fitted with an exhaust fan and air filters. The enclosure
is a 1 i 2-m -diam . cylinder 1. 65 m high; o v er-a ll height is 2. 5 m.
The compacting force is 1300 kg. The device comes equipped with
an integral hydraulic power unit and associated controls.
5.3.
SOLID WASTE BURIAL
5. 3. 1.
Packaging
Solid wastes that are to be buried should be packaged in
a manner such that the contents will not be exposed or released
during the handling, transportation, temporary storage and burial
operatipns. Most of the containers discussed in section 2.3.11 will
70
FIG. 22.
D e v ic e for c o m p a c tin g con ta m in a ted solids and rubbish
meet these criteria, with the exception of cardboard boxes, which
are likely to lose their integrity when exposed to wet weather. Semi
liquid wastes such as evaporator concentrates or chem ical treat
ment sludges should always be solidified with cement or mixed with
vermiculite or other absorbent materials and packaged in metal con
tainers before transportation and burial. Plastic bags which have
been sealed with tape are satisfactory containers for low-level solids
where sharp objects such as broken glassware or metal wastes are
not involved. Plastic bags may also be usefully employed as liners
for the containers discussed in section 2 .3 .1 . as an additional bar
rier between the wastes and ground water.
71
5. 3. 2.
S ite s e le c t io n f o r ground d isp osa l
In selecting a site for ground disposal of radioactive wastes the
objective must be to find a place from which wastes moving through
the soil will not enter the public domain in amounts that could cause
unacceptable radiation exposure of the population.
If the site is sufficiently far from human habitation this object
will be attained. The underground movement of wastes is caused
by the movement of ground water, therefore the absence of ground
water is desirable, but this can seldom be attained. The entry of
waste into ground water introduces a dilution factor as well as en
suring that the movement will probably be slow. Slow movement
ensures time for radioactive decay. However, distance from human
habitation entails high cost of transport, especially if wastes are
sufficiently active to require shielding or special vehicles.
Ground waters move slowly when the head is small, i.e . move
ment in flat country is slower than in hilly country. Clay soils are
less permeable than sands, but it must be rem em bered that soil
horizons are never uniform and water will move more quickly in one
stratum - e .g . a gravel or sharp sand layer - than in another, e .g .
a silt or loam . This demands a rather detailed knowledge of the
local soil stratification. The tendency of clay soils to become water
logged and form surface swamps and streams must be remembered.
Consideration must be given to the nature of the bedrock. Lime
stone frequently contains channels through which water runs at rates
comparable with those in a stream, and granite is frequently fis
sured. The geological situation must therefore be assessed with
these factors in mind.
Many radionuclides are strongly adsorbed into soils, particular
ly silts and clays. This imposes a very important delay upon waste
movement. Even when the cation exchange capacity of soils is low e .g . sands - significant adsorption will usually occur. Some radio
nuclides - e .g . isotopes of Sr, Ru, Cs, Co, S, move more rapidly
than others through soils, but the rate of movement will depend on
the properties of the local soil. For example, caesium moves more
rapidly than strontium through calcareous soil, but the situation is
reversed in acid sand. Thus a knowledge of local soil chemistry is
helpful in site selections, but again it must be remembered that soil
structure is not uniform.
An ideal disposal site should be dry to great depths or be drained
by slow -m oving water flowing through soil with a high cation e x -
72
change capacity, and remaining below ground for a long time. On
emerging into surface water, the ground water would be greatly di
luted by flowing into a large river or tidal water which would not be
used to any significant extent by man.
These site characteristics are usually unobtainable in practice,
so the choice must be made of the best available com prom ise. The
amount of radioactive material premitted to enter the soil will de
pend on the degree to which the requirements can be met. If drainage
from a disposal area can be sampled - e .g . if it em erges at one
point - this will simplify monitoring, and if it could be segregated
and treated at this point the requirements might be somewhat less
strict. A considerable relaxation of requirements would result from
a decision that wastes having more than a set content of radioactive
material per package would be placed in water-tight containers such
as high-quality concrete-lined facilities.
It would appear that more use could be made of municipal dumps
for the disposal of Small quantities of low -level packaged wastes
than has been the case in the past. Such dumps are carefully sited
to prevent contamination of surface and other waters with non
radioactive pollutants. Usually the site, when exhausted, is covered
and used as a park, playground, or for agriculture, for which pur
pose only the topsoil is disturbed. Even if it is developed in other
ways a period of several years will elapse.
It is common practice for local authorities to carry out some
form of salvaging, sorting, incineration or other procedure on solid
waste. This would be undesirable in the case of radioactive material,
and such waste, in consequence, should be.taken directly to the point
of burial and buried beneath at least four feet of other rubbish.
Although the amount of material sent to municipal dumps would
have to be the subject of discussion with the local authorities con
cerned, it would not seem unreasonable to work to the following
limits:
(a) The material should be encased in a suitable container. Nor
mally a 20-gauge drum with a well-fitting lid would suffice.
(b) The estimated amount per container should be less than
100 iuCi of long-lived radionuclides and less than 1 mCi of nuclides
with a half-life less than one year.
(c) The gamma dose-rate at any point on the surface of the
completed container should be less than 20 m r/h.
73
6.
AIR-BORNE WASTE MANAGEMENT
6.1.
FUME-HOOD DESIGN RECOMMENDATIONS
Ordinary chemical fume hoods are often used for handling small
amounts of radioactive material. Many modifications have been made
in their design, the major refinement being to ensure a constant air
velocity at the opening, regardless of the position of the door or
front. Figure 23 shows some ways of achieving this.
EXHAUST
EXHAUST
EXHAUST
MOTOR OPERATEO
f DAMPER AND CONTROL 7 " '
•fHr
PROPORTIONS
D A M P ER -LIN K
OPERATEO
BYPASS~REMOVABLE
FILTERS OR
BLANKS
FIG. 23.
M ethods o f con trollin g fa ce v e lo c it y in r a d io a ctiv e -m a te ria l hoods,
(b ) P roportional by-pass lin k -o p e ra te d ;
pressure) plus dirty filte r resista n ce.
(c ) P roportional b y-pa ss fa c e open in g.
D u ct v e lo c it y = 3 50 0 ft /m in .
Filters:
(a ) Controlled fa ce velocities;
Entry loss = 0.25 VP (v e lo city
(i) P refilter;
(i i) A fte r -filte r ;
(A m e r ic a n C o n fe r e n c e o f G ov e r n m e n ta l Industrial H y g ien ists, "Industrial V e n tila tio n M a n u a l".)
The basic need is to provide sufficient air velocity into the hood
to prevent the outward escape of contaminants. This may result
from abnormal heat loads within the hoods, cross drafts in rooms,
and rapid movements (walking in front of hoods).
The following general rules should be followed in the design of
hoods for radioactive materials:
(1) Operations in which radioactive materials are handled should
be enclosed as much as possible to prevent contaminating
large air volumes.
(2) High velocities and cross drafts should be avoided because
they may increase contamination and dust loading considerably.
74
(3) The volume of air withdrawn from the hood must be greater
than the volume of contaminated gases, fumes or dust
created in the hood.
(4). If possible, the operations requiring large amounts of wet
digestion and volatilized acid or solvent treatment should
be confined to one group of hoods and the handling of dry
material in others.
(5) When levels of radioactivity are such that filtration is r e
quired, radioactive aerosols should be removed by filters
placed as close to the hood as practical to prevent the un
necessary contamination of equipment and duct work.
(6) A ccessibility for decontamination of the hood and the duct
system must be made as easy as possible and quite fr e
quently stainless steel is used for the metal parts of the
hood for this reason.
(7) The fan should be located so that duct work within the build
ing is under a negative pressure.
To provide uniform distribution of flow at the face of the hood,
several methods have been used. A perforated wall located at the
back panel provides better distribution than a panel with slot entry
at the top and bottom. A filter installed in the hood panel before the
plenum is satisfactory in most instances and it can be easily changed
when it becomes loaded or dirty. It is desirable to check the veloci
ty through the hood opening at regular intervals to see whether the
filter has become clogged.
The laboratory will normally be ventilated through the fume hood
and to maintain adequate air changes when the hoods are not in use
a by-pass system is necessary. The hoods may be down-draft or
up-draft with the proportional by-pass overhead or at floor level.
An alternative approach to having a hood with a constant air ve
locity is to design the system to give an average face velocity of
about 200 ft/min (60 m/min) with the door or sash open in the work
ing position. This is usually 1. 5 ft (45 cm) high.
As this velocity may lead to large air-heating requirements some
allowance is normally made in the design for the fact that all the
fume hoods will not be used simultaneously, but such diversity fac
tors should be used with caution.
The average face velocity of 130 ft/m in (40 m /m in) is optimal
for most fume cupboards. As absolute minimum the velocity should
not fall below 100 ft/m in (30 m /m in). As it was already.mentioned,
for some special purposes higher velocities may be necessary. How
75
ever, above velocities of approximately 150 ft/min (45 m/min) with
dry (i.e . powder) operations, there is a danger that considerable
and unnecessary quantities of radioactive material will be exhausted
from the fume hood spreading contamination through the exhaust duct
system, clogging the filters, thereby necessitating frequent filter
changes and also increasing the contamination and radiation hazards.
Also, there is a danger with pyrophoric powders of creating a fire
hazard. With other types of operations done in fume cupboards it
has been found that, with linear velocities in excess of 200 ft/m in
(60 m /min), pieces of paper, e .g . tissues, will be sucked into the
exhaust system thereby blocking filters and tending to cause a fire
hazard.
6 .2 .
GASEOUS AND AEROSOL WASTE CONTROL SYSTEMS
SUITABLE FOR USE BY SMALL LABORATORIES
For- most uses of radioisotopes in the quantities usually associ
ated with small laboratories, the purification of exhaust air streams
is unnecessary, provided that the exhaust outlet is suitably placed.
In cases where direct discharge would create an unacceptable hazard,
systems such as those described below may be used to remove radio
active aerosols and gases from the effluent air stream. However,
it must be emphasized that the design and installation of anything
more than the simplest types of exhaust and air-cleaning equipment
should be undertaken only by specialists in these fields.
6. 2. 1.
High-efficiency filters
The extrem ely low perm issible level of air activity in radio
active work has required a filter capable of giving high removal ef
ficiencies, often better than 99. 95% for submicron particles. These
filters must sometimes remain intact at high temperatures, or at
high humidities during norm al operation o r during an accident.
Most of the materials used in high-efficiency filtration are of a
fibrous nature, and the filters consist of an assem bly in depth of
fibres of suitable diameter. The packing density of the fibres may
vary from a loosely packed pad to a compressed paper, but the di
mensions of the fibres and of the pores between them are, in general,
greater than those of the particles being filtered. The filter does not
act simply as a sieve, but aerosols are arrested by direct inter
76
ception, inertial impaction, diffusion, electrostatic attraction and
gravitational effects.
Many materials are available for forming fibrous media suit
able for filtration: some m aterials, e .g . asbestos/w ool mixture,
are form ed into pads which are made up in filter cases of flat or
cylindrical construction. While such filters can have very high ef
ficiencies (up to 99. 9995%) and satisfactory pressure drops (~ 0 .4 in
(10 mm) water gauge for face velocities up to 25 ft/min (7.5 m/min))
they are rather bulky and less used in modern installations.
More attractive are materials which can be form ed into a lap
that can be pleated around spacers such that a large surface can
be presented to the air flow in a small volume.
Materials which can be used in this way include:
(a)
Glass paper ~ made from very fine glass fibre (1 - 2 /nm diam .)
The fire-resistant nature of this filter has made it particularly
attractive for radioactive installations. A wide range of sizes are
available, from about 3 ft3/m in to 1000 ft3/m in. The dimension of
a filter unit with a capacity of 1000 ft3/m in need only be 2 ft X 2 ft X 1ft
(60 cmX 60 cmX 30 cm). Larger installations contain banks of unit s .A typical face velocity is 3 - 5 ft/min (1-1.5 m/min) with a pressure
drop of about 1 in (25 mm) water gauge. The glass paper is pleated
around spacers of corrugated aluminium and sealed with fireproof
cement into a mild steel frame. When inserted into wall panels or
canisters, the leading edge of the filter insert is sealed against a
face in the filter assembly by means of a glass paper gasket. The
whole assem bly is designed to remain intact and not contribute to
combustion on heating to 500°C.
(b) P aper - made from a m ixture of asb estos and ce llu lo se
These filters are very similar in design and performance to the
glass, paper type. The spacers are often of corrugated kraft paper
and the frame may be wooden. They are hyroscopic, not fire r e
sistant and are gradually being displaced by the glass-fibre paper.
(c)
Cotton-asbestos mixture
These filters were widely used for radioactive work a few years
ago and provided very high efficiencies, approximately 99. 99% with
77
submicron dusts. They are not fire resistant and tend to weaken
at high humidities.
6. 2. 2.
Medium-efficiency prefilters
Where the dust loading is high it may be necessary to precede
the high-efficiency filter by a coarser pre-filter to prolong its life.
This pre-filter is often of glass or synthetic fibre with diameter of
20 - 30 /urn.
After a period of operation the dust loading on the filter and con
sequently the pressure drop in crea ses. At this stage it becom es
necessary to replace the filter. This involves special techniques
to protect the operators, to prevent contaminati6n spreading out
side the filter installation and to confine the activity within the filter
element which is being removed. Many fibre and paper disposable
filters are available but in the case of radioactive filtration plant a
pleated pad of glass fibres several inches thick has been most com
monly used. This coarse glass-fibre pad also serves as an excellent
spark arrester giving protection to the main filters. E fficiencies
> 90% are obtained for particles down to 0. 5 jum. The pressure drop
at the beginning of its life is usually 0. 5 in. (12 mm) w .g. Replace
ment of pre-filters is often an economic matter as their cost is usu
ally much less than that of the main filters. The useful life of a pre
filter may vary from a few weeks to perhaps a year depending on the
dust load in the air. As a general rule the pre-filter would be
changed when the pressure drop increases by a factor 3 or 4.
6. 2. 3.
Activated carbon adsorbents
These are efficient and cheap adsorbents which will remove
practically any radioactive vapour or gas from air and other gases.
They are especially suitable for trapping the vapours of both organic
and inorganic labelled compounds (during synthesis) and for remov
ing radioactive iodine and phosphorus and their compounds from air.
Even a comparatively thin layer of activated carbon (20-30 cm) will
remove 99. 9% of the iodine from air at a filtration rate of up to
1 m /m in. The pressure drop of such a layer at the indicated fil
tration rate is not more than 20 mm water gauge. Usually m icro porous carbon is used (to get more effective capillary condensation),
with granule sizes of 6 -1 4 mesh and good mechanical stability, since
dust formation may lower the ignition temperature. Vegetable car
78
bons are the best, for instance those obtained from birch, from
stones of amygdalaceous plants, from coconut shells and the like.
The volume density of such carbons reaches 0.55 g /c m 3.
When a sorbent is used to remove relatively short-lived con
taminants such as 1311 and 32P, it can be automatically regenerated
owing to the radioactive decay of the adsorbed material; this is not
true, however, in the case of labelled compounds, in which the num
ber of. molecules containing the radioisotope is small compared with
the number of non-radioactive molecules. .
Activated carbon is the best adsorbent for radioactive inert
gases as well. Its disadvantage lies in the fact that it is compara
tively easily inflammable. Although the ignition point of carbon in
a flow of air normally lies about 200°C, it is safer to limit the tem
perature of the adsorber to 100-150° C when gases containing oxygen
are to be filtered. This makes, carbon practically useless for de
contaminating gases that contain strong oxidizing agents (e .g . ap
preciable concentrations of nitric oxides).
REFERENCES
N ote:
Chapter 2: Waste C ollection Containers and Systems
Main References:
Chapter 3:
Main References:
Chapter 4:
[7, 13, 14, 16, 21, 22],
Liquid Waste Treatment Techniques Suitable for Users o f Radioisotopes
M ainReferenc.es:
Chapter 5:
[1, 2, 5, 6, 8, 9. 11, 17, 19, 24, 25, 27, 28, 29, 30, 31, 32]
Solid Waste Treatment and Disposal by Individual Users o f Radioisotopes
Main References:
Chapter 6:
[3, 4, 7, 10, 20, 22, 23, 24, 26, 27, 32]
A ir-born e Waste Managem ent
Main References:
[1 ]
[3, 10, 15, ,18, 24, 27, 32]
Direct Disposal o f R adioactive Wastes to Sewers
[12].
AMPHLETT, C .B ., SAMMON, D . C . , "Survey o f Treatments Considered for L ow -A ctivity
Wastes", in A tom ic Energy Waste, Its Nature, Uses and Disposal (Ed. E. Glueckauf), Inter
science Publishers, New York, and Butterworth and C o ., London (1961).
[2]
ANON.,
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[3]
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Establishment, Harwell” , Disposal o f R adioactive Wastes, _1, IAEA, Vienna (1960).
[4 ]
BURNS, R. H .,
"T h e Disposal o f R adioactive Solid Wastes" in R adioactive Wastes, Their
Treatm ent and Disposal (Ed. T. C . C ollin s) E. and F .N . Spon L im ited , London (1 96 0 ).
79
[5]
[6]
BURNS, R. H ., GLUECKAUF, E ., "Development o f a Self-Contained Scheme for Low-Activity
Wastes", Proc. 2nd UN Int. Conf. PUAE 18 (1958) 150.
CHRISTENSON, C .W ., et a l . , "Rem oval o f Plutonium from Laboratory W astes", Ind. Eng.
Chem . 43 (1951) 1509-15.
[7]
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US Government Printing O ffice, Washington, DC (1962).
[8 ]
COWSER, K. E.
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o f Low Level W astes", Proc. 2nd UN Int.
161.
DEJONGHE, P. et a l . , "Treatm ent o f Radioactive Effluents at the Mol Laboratories", Proc.
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[10]
ENDERS, J .W ., "Radioactive Trash Disposal at Los Alam os", J. Amer. industr. Hygiene Assn.,
[11]
2 1:2 (1960).
GOFF, D .L ., BLOORE, E .W ., THIEME, A .,
ment F a cility ", NDL-TR-61,
"A Sem i-fixed Radioactive Liquid Waste Treat
US Army Nuclear Defense Laboratory, Edgewood Arsenal,
Maryland (in press).
[12]
INTERNATIONAL ATOMIC ENERGY AGENCY,
"Techniques for Controlling Air Pollution
From the Operation o f Nuclear F acilities", IAEA, Vienna, (in press).
[13]
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION,
"Report of C om m ittee II
on Permissible Dose for Internal Radiation", Publication 2, Pergamon Press (1959).
[14]
INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION.
"Report o f Com m ittee V
on the Handling and Disposal o f R adioactive Materials in Hospitals and M ed ica l Research
Establishments", Publication 5, Pergamon Press (1965).
[15]
IOSEPH, A .B .,
"R ad ioactive Waste Disposal Practices in the A to m ic Energy Industry, A
Survey o f the Costs", Rept. NYO 7830 (1955).
[16]
KENNEY, A. W ., "T h e Behaviour o f Radioisotopes in Sewage Treatm ent and the Disposal
[17]
LAUDERDALE, R. A. I r . ,
[18]
MAWSON, C .A .,
o f R adioactive Wastes to Sewers",
J. Brit. nucl. Energy C onf. 2 (1957).
"Studies on the Rem oval o f Radioisotopes from Liquid Wastes by
C oagulation", Rept. ORNL 932 (1951).
"Management of Radioactive Wastes", D. Van Nostrand C o ., I n c ., Prince
ton, N.J. (1965).
[19]
MEAD, F .C ., Jr.,
"Som e Observations on the Decontam ination o f Fission Product Wastes"
in Sanitary Engineering C onference Proceedings, USAEC Report WASH 275 (1954).
[20]
MORGAN, J. M ., Jr. et a l., "Land Burial o f Solid Packaged Low Hazard Potential R adio
active Wastes in the United States", Proc. C onf. on Ground Disposal o f Radioactive Wastes,
Chalk River, Canada, Sept. 1961, Rept. TID-7628.
[21]
NATIONAL COMMITTEE ON RADIATION PROTECTION, "Recomm endations for Waste Dis
posal o f Phosphorus-32 and Iodine-131 for Medical Users", National Bureau o f Standards Hand
book 49. Govt. Printing O ffice, Wash. D .C . (1951).
[22]
PCHELINTSEVA, G . M ., e d ., "Sanitary Regulations for Work with R adioactive Substances
and Sources of Ionizing Radiation", State Publishing House o f Literature in the Field of Atomic
Science and Technology, Moscow (1960).
[23]
PECKHAM, A.E. and BELTER, W .G ., "Considerations for Selection and Operation o f Radio
a ctiv e Waste Burial Sites", Proc. C onf. on Ground Disposal o f R adioactive Wastes, Chalk
River, Canada, Sept. 1961, Rept. TID 7628.
[24]
80
RODGER, W. A . , "R adioactive Waste Disposal", Rept. ANL-6233 (1960).
[25]
SCHULTZ, W .W ., McKENZIE, T. R ., "The Removal of Cesium and Strontium From Radio
active Waste Solutions" in Sanitary Engineering Aspects of the Atom ic Energy Industry, USAEC
Report TID-7517 (1956).
[26]
SILVERMAN, L. B. and DICKEY, R. K ., "Reduction of Combustible, Low-Level Contaminated
Wastes by Incineration", UCLA-368 (1956).
[27]
STRAUB, C .P ., "Low -Level Radioactive Wastes, Their Handling, Treafment and Disposal",
[28]
STRAUB, C. P ., et al.
[29]
SWOPE, H .G ., "Treatment o f Radioactive Wastes" in Ion Exchange Technology, (Ed. Nachod,
U .S. Government Printing O ffice, Washington, D .C .
(1964).
"Method for Decontamination of Low Level Radioactive Liquid Wastes",
Proc. 1st UN Int. Conf. PUAE 9 (1956) 24.
F .C . and Schubert, J.) A cadem ic Press, In c., New York (1956).
[30]
SWOPE, H .G ., ANDERSON, E ., "Cation Exchange Removal o f Radioactivity from Wastes",
[31]
TALSKY, J ., "Decontam ination o f Radioactive Effluent by C hem ical Precipitation", Waste
[32]
UNITED STATES CONGRESS, Joint C om m ittee on A tom ic Energy, Special Subcom m ittee on
Industr. Engng Chem . 47 (1955) 78-83.
Management Research Abstracts No. 1, IAEA, Vienna (1965).
Radiation, Industrial R adioactive Waste Disposal,
Washington, D .C . (1959).
"Hearings"', G ovt.
Printing O ffic e ,
81
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Technical Addendum - GNSSN Home - International Atomic Energy

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