Schulz H - EAN-NORM

Transcription

Schulz H - EAN-NORM

IAF - RADIOÖKOLOGIE GMBH
Labor
Labor für
für Radionuklidanalytik
Radionuklidanalytik Radioökologische
Radioökologische Gutachten
Gutachten Consulting
Consulting
„Dose assessment for workers at
mercury recycling of sludge and scale from
natural gas production“
Hartmut Schulz
IAF - Radioökologie GmbH. Karpatenstraße 20
01326 Dresden
Wolfgang Mothes
GMR Gesellschaft für Metallrecycling mbH,
Naumburger Str. 24
04229 Leipzig
Labor
Labor für
Consulting
Dose assessment for workers at
mercury recycling of sludge and scale
from natural gas production
• About Scale and Sludge
• Radiological measurements and dose
assessment at the recycling of mercury and
the immobilisation of the residues
• Radiological measurements and dose
assessment at the disposal of immobilised
residues at a landfill
EANNORM “Scenarios for Dose Assessments in the NORM industry"
23. - 25. November Dresden
2
Labor
Labor für
Consulting
What is the topic
NORM: Scale and
Sludge
containing Mercury
gas production plant
near
Transport
Leipzig
Recycling of
Mercury
ive es
t
c
ioa ilisat
d
ra
ob
m
im
Mercury
Marketing
landfill
3
Labor
Labor für
Consulting
Typical scale in tubings
Scale thickness up to 5 mm
• Scale mass 4 to 10 kg per 10 m tubing
• 2 to 5 tons in 5 km length of pipeline
• 0 - 8 %mass percent mercury
4
Labor
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Consulting
Mercury drops in a typical sludge
• 8 - 15 %mass percent
mercury
• but also up to 30% possible
• The mercury drops contain
always Pb-210
• typical values: 5 - 10 Bq/g
(/gram mercury)
5
Labor
Labor für
Consulting
5 Relevant radionuclides in the residues
(sludge and scale)
U-238 decay series: Ra-226, Pb-210, Po-210
Th-232 decay series: Ra-228, Th-228
U-238 < 1 Bq/g
Practically
of minor importance
Th-232 < 1 Bq/g
After 30 years practically no Ra-228 and Th-228
in the residues!
6
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Consulting
A(Ra-228) ≈ A(Th-228) after 4 years
years
7
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Consulting
Typical radionuclide compositions at the
beginning and after 20 years
450
400
At the beginning
350
[Bq/g]
300
Pb-210 [Bq/g]
250
Ra-228 [Bq/g]
200
Th-228 [Bq/g]
150
100
50
0
0
100
200
300
400
500
350
600
Ra-226 [Bq/g]
300
[Bq/g]
250
200
Pb-210 [Bq/g]
Ra-228 [Bq/g]
after 20 years
150
Th-228 [Bq/g]
100
50
0
0
100
200
300
400
500
600
Ra-226 [Bq/g]
8
Labor
Labor für
Consulting
Radionuclide compositions after
50 and 100 years
500
450
after 50 years
400
350
[Bq/g]
300
Pb-210 [Bq/g]
250
Ra-228 [Bq/g]
Th-228 [Bq/g]
200
150
100
50
0
0
100
200
300
400
500
600
600
[Bq/g]
Ra-226 [Bq/g]
500
after 100 years
400
Ra-226 ≈ Pb-210
Pb-210 [Bq/g]
Ra-228 [Bq/g]
300
Th-228 [Bq/g]
200
100
0
0
100
200
300
400
500
600
Ra-226 [Bq/g]
9
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Consulting
Distribution of Radionuclides in a gas
production pipe (length 5 km)
bottom
[m]
surface
10
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Consulting
Activity ratios from the bottom to the
surface (gas production pipe 5 km length)
bottom
[m]
surface
11
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Consulting
Density [g/cm³]
Thickness [mm]
density and thickness of scale in a gas
production pipe
Thickness
Density [g/cm³]
bottom
[m]
surface
12
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Consulting
Gamma dose rates of barrels with residues
(Scales from hydrocleaning, high pressure
cleaning or waterblasting, 2000 bar)
20
80 barrels, mass 14 t
15
Mean value gamma
dose rate: 8,8 µSv/h
Häufigkeit
mean value Ra-226: 30 Bq/g
10
5
0
0
4 8 12 16 20 24 28 32 36 40 44 48
[µSv/h]
13
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Consulting
Ra-226 distribution in barrels with sludge
60
experimental
frequency Ra-226
lognormal distribution
50
Frequency
40
172 barrels with
sludge,
Mean value Ra-226: 10,9 Bq/g
Mass: 17 tons
Median: 3,8 Bq/g
30
20
10
0
0
4
8
12 16 20 24 28 32 36 40 44 48
[Bq/g]
14
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Consulting
Pb-210 distribution in barrels with sludge
30
172 barrels with
sludge,
experimental frequency
Pb-210
lognormal distribution
Mass: 17 tons
Mean value Pb-210: 22,5 Bq/g
Frequency
20
Median: 9,8 Bq/g
10
0
0
4
8
12 16 20 24 28 32 36 40 44 48
In average
specific Pb-210
activity of sludge
larger than that
of Ra-226
[Bq/g]
15
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Consulting
Typical activity ranges in Sludge and Scale
Sludge [Bq/g]
Scale [Bq/g]
Ra-226
up to 150
5 - 500
Der Vortrag kann auf der IAF Webseite
Ra-228
30
1 - 350
www.IAF-Dresden.de heruntergeladen weden
Th-228
depending on age
depending on age
Pb-210
up to 500
1 - 500
Po-210
(depending on age)
depending on age
Specific activities of U-238 und Th-232 mostly
below 1 Bq/g.
16
Labor
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Consulting
Radon Generation of Dry Scales
Exhalation box
in a closed tubing 25.000 Bq/m³
[ hours ]
Schichtdicke
[ thickness ]
[mm]
2,7
Ra-226
[Bq/g]
440
of radon could be reached
[Exhalationsrate
exhalation rate ]
[Exhalationsrate
exhalation rate ]
[Bq/(m² s)]
0,0068
[Bq/(m² h)]
25
Diffusionskonstante
[ diffusion
parameter ]
[m²/s]
5,5⋅⋅10-18
17
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Consulting
Radon Generation of Sludge
Practically
radon exhalation of sludge
of minor importance
Why?
Radon Oil-Water distribution
coefficient (Kd) is rather large!
Diesel / Water
Benzine / Water
Air / Water
Kd
39,8 ± 4
52,3 ± 6
≈4
c Oil
K
d
=
c
W
 Bq
 l
 Bq
 l




18
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Consulting
Mercury recycling process
90 - 95
mass%
„waste“
Sludge and/or Scale
dry mineral
radioactive residues
of the recycling
process
Evaporation and condensation
for extraction of raw-mercury
raw mercury
5 - 10 mass%
Multi-level
purification
Marketing
19
Labor
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Consulting
Preparatory work
Radiation
Protection
Preparatory work
Taking over the NORM residues
Transport of NORM (ADR 7)
from somewhere to Leipzig
Reception and Inspection control in
Leipzig
Temporary Storage of NORM
Compilation of Charges
for the production process
(de-mercurisation)
yes, not
considered
yes, not
considered
yes
yes
no
20
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Ongoing work
Vacuothermal de-mercurisation
RP
yes
Immobilization of the dry residues
RP
yes
Disposal at a landfill
RP
yes
21
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Take-over room
22
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Consulting
Storage of sludge and scale
23
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Consulting
Plant for de-mercurisation
24
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Consulting
Storage of dry mineral residue after the
de-mercurisation process
25
Labor
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Equipment for making the immobilisates
(about 1:1 mixture of NORM residues and
geo-polymer)
26
Labor
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Consulting
Radiological measurements for dose
assessment
•
•
•
•
Radon measurements
Gamma rate measurements
Dust measurements (α
α- and γspectroscopy)
Radionuclide analyses (α
α- and
γ-spectroscopy)
27
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Consulting
Radon concentration in taking-over storage
• average over 3 weeks: 20 Bq/m³
200
32
• Radon concentration comparable
to that of the atmosphere
150
28
20
100
16
[°C]
[Bq/m³]
24
12
50
8
4
0
20.6.10
0
22.6.10
24.6.10
26.6.10
28.6.10
30.6.10
2.7.10
Taking over storage
4.7.10
6.7.10
8.7.10
10.7.10
Temperature
28
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Consulting
Radon concentration in the storage
average over 3 weeks: 855 Bq/m³
average during work: 200 Bq/m³
34
3000
32
30
2500
weekend
28
26
24
22
20
18
1500
16
[°C]
[Bq/m³]
2000
14
12
1000
10
8
6
500
4
2
0
0
21.6.10 22.6.10 23.6.10 24.6.10 25.6.10 26.6.10 27.6.10 28.6.10 29.6.10 30.6.10
1.7.10
storage
2.7.10
3.7.10
4.7.10
5.7.10
6.7.10
7.7.10
8.7.10
9.7.10
10.7.10
temperature
29
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Consulting
Why elevated Radon concentrations?
•
•
•
•
•
Residues after the de-mercurisation are
almost dry,
no volatile organic compounds,
emanation factor E: 0,2 - 0,6
specific Ra-226-activity fairly high
stored in big bags
Not radon tight
30
Labor
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Consulting
Radon concentration in production plant
300
38
36
34
32
250
• closed system and ventilation
30
28
26
200
22
20
150
18
[°C]
[Bq/m³]
24
16
14
100
12
10
8
50
6
4
2
0
0
20.6.10 21.6.10 22.6.10 23.6.10 24.6.10 25.6.10 26.6.10 27.6.10 28.6.10 29.6.10 30.6.10 1.7.10
production plant
2.7.10 3.7.10
4.7.10
5.7.10 6.7.10
7.7.10 8.7.10
9.7.10 10.7.10 11.7.10
emperature
31
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Consulting
Radon concentration in immobilisation room
600
500
• average during work: 28 Bq/m³
• Efficient ventilation system
30
28
26
24
22
20
18
weekend
16
300
weekend
[°C]
[Bq/m³]
400
14
12
200
10
8
6
100
4
2
0
0
22.7.10 23.7.10 24.7.10 25.7.10 26.7.10 27.7.10 28.7.10 29.7.10 30.7.10 31.7.10
doing immobilisation
1.8.10
2.8.10
immobilisation room
3.8.10
4.8.10
5.8.10
6.8.10
7.8.10
8.8.10
9.8.10
10.8.10
temperature
32
Labor
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Consulting
Summary: Radon exposure
work
• taking-over,
compiling charges
• handling in the
storage
• de-mercurisation
• immobilisation
sum
Exposure
Radon
Dose
time
concentration
[mSv]
[h]
[Bq/m³]
100
20
0,01
200
200
0,12
1200
300
1800
30
28
0,11
0,03
0,27
33
Labor
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Consulting
Summary: gamma rate measurements
taking-over
[µSv/h]
storage
[µSv/h]
0,24
0,98
taking-over
[mSv]
storage
[mSv]
0,014
0,118
production
plant
[µSv/h]
0,33
equipment for
immobilisation
[µSv/h]
0,42
production
plant
[mSv]
0,238
equipment for
immobilisation
[mSv]
0,076
34
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Summary: external exposure
work
• taking-over,
compiling charges
• handling in the
storage
• immobilisation
sum
Exposure time
[h]
Gamma dose rate
[nSv/h]
Dose
[mSv]
100
240
0,014
200
980
0,118
1200
300
1800
330
420
0,238
0,076
0,45
35
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Inhalation of Dust
We quantify the dust deposition by measuring
the total activity of the used masks!!
Very often
dominating together
with Po-210
Most effective and accurate method!!
Example:
10 days of
deposition
worker
1
2
Ra-226
[Bq]
0,6
1,7
Ra-228
[Bq]
0,15
0,4
Th-228
[Bq]
0,14
0,44
Pb-210
[Bq]
1,4
4,4
36
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Exposure due to Inhalation of Dust
worker
exposure
time
[h]
Dose
without mask
[mSv]
Dose
with mask
[mSv]
1
2
1800
1800
0,24
0,74
0,024
0,074
Without masks one could easily get an
exposure exceeding 1 mSv/year!!
37
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Total doses for de-mercurisation and
immobilisation
work
• taking-over,
compiling
charges
• handling in the
storage
• immobilisation
sum
Exposure
time
[h]
Inhalation
External
radon and Total Dose
exposure
dust
[mSv]
[mSv]
[mSv]
100
0,014
0,014
0,028
200
0,118
0,128
0,246
1200
300
0,238
0,076
0,45
0,16
0,042
0,34
0,398
0,118
0,79
1800
Due to radiation protection measures total
exposure dose < 1 mSv/year for workers
38
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Immobilization with geo-polymer
dry mineral
radioactive residues
of the recycling
process
Immobilization of the residues
by addition of a polymer
(geo-polymer)
mixing ratio: about 1 : 1
Up to 250 kg in
a 120 l barrel
ready for
disposal
39
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Characteristics of the Immobilisate made
with geo-polymer
Long term stability,
Like Hardened Concrete,
weather-proof
old mortar similar
to geo-polymer
concrete
negligible elution
of harmful substances
(radionuclides,
heavy metals, arsenic)
No Exposure via the water path
40
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Elution of Immobilisates
Sample
Ra-226
Ra-228
Th-228
Pb-210
Po-210
[Bq/g]
[Bq/g]
[Bq/g]
[Bq/g]
[Bq/g]
1
18
8,85
9,1
3,2
3,2
2
61
11,4
15
80
80
Ra-226
Ra-228
Th-228
Pb-210
Po-210
[Bq/l]
[Bq/l]
[Bq/l]
[Bq/l]
[Bq/l]
1
<0,02
<0,008
<0,02
<0,02
0,018
2
<0,09
0,015
<0,01
0,12
0,005
Eluate
Eluate has a quality comparable to that of „mineral
water” concerning concentration of radionuclides
no exposure along the water path
41
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Advantage of the Immobilisate made with geo-
polymer
Negligible
low exhalation
of radon
No formation of dust
at handling, transportation
and disposal
No elution
of radionuclides
after disposal!!
No internal
exposition
External Exposition
due to Gamma
Radiation
is the only
Exposure Pathway
42
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According to § 98 of the German Radiation
Protection Ordinance the de-mercurised
residues are released
The criterion is:
The effective dose should not exceed
1 mSv/year (reference value for persons of the
population).
The values of the specific activities of the
relevant radionuclides play practically no role!
43
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Transport to the landfill
near
Leipzig
Recycling of
Mercury
landfill
ive es
t
c
ioa ilisat
d
ra
ob
m
im
Mercury
44
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Consulting
Barrels filled with immobilisates ready for
the transport to the landfill
45
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Consulting
Transport: Radioactive, ADR 7
46
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Radiological characteristics of a typical
loading to be disposed
30
48 barrels,
mass: 11,1 tons
25
Mean values
Ra-226: 12,2 Bq/g
Pb-210: 19,0 Bq/g
[Bq/g]
20
15
Gamma dose rate:
3,8 µSv/h
10
Ra-226
Pb 210
5
0
0
2
4
6
[µSv/h]
47
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Gamma dose rate in the driver‘s cab
µSv/h
0,58
48
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Transport on street to the landfill
Distance to the landfill 13 km
Driving time: 15 minutes
Gamma dose rate in the
driver‘s cab: 0,3 - 0,6 µSv/h
landfill
15 transportations per year to
the landfill
Exposure dose of the driver:
<2 µSv/year
49
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Work at the landfill
Handling and storing the
barrels: 15 minutes
Distance of the worker to the
barrels 3 - 5 meters
Gamma dose rate: <0,3 µSv/h
landfill
Exposure dose of the worker
at the landfill:
<2 µSv/year
50
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Summary
• Despite the fact, that we are dealing with
rather elevated specific activities of the
relevant radionuclides, the exposure doses
can be kept low by applying necessary
Radiation Protection measures.
• The immobilisation of de-mercurised
sludge and scale has the great advantage,
that a very stable deposition of
hazardous residues can be achieved.
51

Schulz H - EAN-NORM

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