Test Manufacture of a Canister Insert

Transcription

Working
Repor t
2003-59
Test Manufacture
of aCanister Insert
Heikki
Raiko
VTT P rocesses
November
2003
Working Reports contain information on work in progress
or pending completion .
The conclusions and viewpoints presented in the report
are those of author(s) and do not necessarily
coincide with those of Posiva .
Research organisation and address
Customer
VTT Processes, Nuclear Energy
P.O. Box 1608
FIN-02044 VTT, FINLAND
Posiva Oy
27160 OLKILUOTO
Project manager
Contact person
Heikki Raiko
Nils-Christian Wikstrti~
Diary code (VTT)
Order reference
PRO 1/7045/03
9516/03/NW
Project title and reference code
Report identification & Pages
Date
Kapselointitekniikkaan liittyva tutkimus- ja kehitystoiminta
13KAPSTEKN03, C3SU00163
PRO 117045/03
17 p. + App. 4 p.
6.11.2003
1"&Jd..
'""2. o ~ If,
2.oo 3
Report title and author(s)
TEST MANUFACTURE OF A CANISTER INSERT
Raiko, Heikki
Summary
This report describes the insert-manufacturing test of a disposal canister for spent nuclear fuel that
was made by Metso Paper Oy, JyvaskyHi Foundry, in 2003 on contract for Posiva Oy.
The test manufacture was a part of the co-operation development programme of encapsulation
technology between SKB AB and Posiva Oy.
Insert casting was specified according to the current manufacturing specifications of SKB. The
canister insert was of BWR-type with integral bottom. This was the first trial manufacture of this
type of insert in Finland and, in total, the second test manufacture of insert by Metso Paper.
The result fulfilled all the requirements but the material mechanical properties and metallurgical
structure of the cast material. The measured tensile strength, ultimate strength and elongation at
rupture were lower than specified. The reason for this was revealed in the metallurgical investigation of the cast material. The nodulizing of the graphite was not occurred during the casting process according to the requirements.
Distribution
Publicity
Posiva 2 ex.
Confidential
Pr~jiJt manage/7) . j
r'
Reviewed and approved by
([G..-«<l/(W 'f~ ;U lt c---C-- s~ ~
Heikki Raiko
Arto Muurinen
Group manager
Research manager
The use of the name of the Technical Research Centre of Finland (VTT) in advertising or publication in part of
this report is only permissible by written authorisation from the Technical Research Centre of Finland
Abstract
This report describes the insert-manufacturing test of a disposal canister for spent nuclear fuel that was made by Metso Paper Oy, J yvaskyHi Foundry, in 2003 on contract
for Posiva Oy.
The test manufacture was a part of the co-operation development programme of encapsulation technology between SKB AB and Posiva Oy.
Insert casting was specified according to the current manufacturing specifications of
SKB. The canister insert was of BWR-type with integral bottom. This was the first trial
manufacture of this type of insert in Finland and, in total, the second test manufacture of
insert by Metso Paper.
The result fulfilled all the requirements but the material mechanical properties and metallurgical structure of the cast material. The measured tensile strength, ultimate strength
and elongation at rupture were lower than specified. The reason for this was revealed in
the metallurgical investigation of the cast material. The nodulizing of the graphite was
not occurred during the casting process according to the requirements.
Keywords: canister insert, nodular cast iron, disposal canister for spent nuclear fuel
LOPPUSIJOITUSKAPSELIN SISAOSAN KOEV ALMISTUS
Tiivistelma
Tassa raportissa kuvataan kaytetyn ydinpolttoaineen loppusijoituskapselin s1saosan
valmistuskoe, joka suoritettiin Metso Paper Oy:n Jyvaskylan valimossa vuonna 2003
Posi va Oy:n toimeksiannosta.
Koevalmistus oli osa SKB AB:n ja Posiva Oy:n valista kapselointiteknologiaa koskevaa
yhteistyossa tehtavaa teknologian kehitysohjelmaa.
Sisaosan valun laatutavoitteet oli maaritelty SKB:n senhetkisten valmistusspesifikaatioiden mukaisesti. Kanisterin sisaosa oli BWR-polttoaineelle tarkoitettua tyyppia ja siina oli kiintea pohjapaaty. Valmistuskoe oli talla sisaosatyypilla ensimmainen Suomessa
suoritettu ja kaiken kaikkiaan Metso Paperin suorittamana valukokeena toinen.
Valmistuskokeen tulokset tayttivat vaatimukset kaikilta muilta osin paitsi valumateriaalin mekaanisten ominaisuuksien ja metallurgisen rakenteen osalta. Mitatut vetolujuuden,
murtolujuuden ja murtovenyman arvot jaivat vaatimusten alapuolelle. Syy tahan paljastui valumateriaalin metallografisessa tutkimuksessa. Grafiitin palloutuminen ei ollut
tapahtunut valussa vaatimusten mukaisesti.
Avainsanat: kanisterin sisaosa, pallografiittirauta, kaytetyn ydinpolttoaineen loppusijoituskanisteri.
1
CONTENTS
Abstract
Tii vistelma
1
IN"TRODUCTION .................................................................................................. 2
2
IN"SERT SPECIFICATION ..................................................................................... 3
3
DESCRIPTION OF PREPARIN"G THE CASSETTE AND MOULD
MANUFACTURE .................................................................................................. 4
4
CASTIN"G ................................................................................................................ 5
5
CLEANIN"G AND CUTTIN"G THE CAST ............................................................ 6
6
DIMENSIONAL CONTROL BEFORE MACHINING ........................................ 7
7
MACHININ"G ......................................................................................................... 8
8
DIMENSIONAL CONTROL AFTER MACHININ"G ........................................... 9
9
MATERIAL TESTIN"G ........................................................................................ 10
10
SUMMARY .......................................................................................................... 17
APPENDIX 1: Photographs from manufacturing phases ............................................... 18
2
1
INTRODUCTION
This report describes the insert-manufacturing test of a disposal canister for spent nuclear fuel that was made by Metso Paper Oy, Jyvaskyla Foundry, in 2003 on contract
for Posi va Oy.
The test manufacture was a part of the co-operation development programme of encapsulation technology between SKB AB and Posiva Oy. The SKB identification for this
insert is 127.
3
2
INSERT SPECIFICATION
The insert test manufacture was ordered according to following specifications.
The steel profile cassette used as the central core of the cast is given in drawing SKB
00004-121, revision E. The cast iron insert as pre-machined is given in drawing SKB
00004-122, revision D. The test gauge for the dimensional test of the openings is given
in drawing SKB TEST 00002, revision B.
The steel profile cassette assembly and the details of the fixing attachments can be
modified according to engineering expertise. Also, the structure of the dimensional test
gauge can be modified for better practicability.
Technical specification for profiles in the steel section cassette is given in SKB technical specification no KTS022, revision 0. The specification for the steel section cassette
is given in KTS021, revision 2. And finally the specification for the nodular cast iron
EN1563 insert is given in KTS011, revision 2.
Procedure instructions are given for "requirements on 1) quality plan, 2) manufacturing
and inspection plan", for "identification of canister components", for "control of inspection, measuring and test equipment" in documents: KT 0704, revision 3, KT 0705,
revision 2, KT 0801, revision 1, KT 1102, revision 2, and KT 1103, revision 2.
In addition, due to first test manufacture of this type of insert in the foundry, an additional destructive material testing was specified according to specification KTS011,
paragraph 6.2 for three sections of the cast; top, middle and bottom.
4
3
DESCRIPTION OF PREPARING THE CASSETTE AND MOULD MANUFACTURE
The steel profile cassette was manufactured at a subcontractor to the JyvaskyHi foundry.
Therefore, a detailed stepwise procedure plan was made to assure the demanding manufacture and control sequence including detailed documentation.
The square steel tubes used for the cassette was made of Rautaruukki cold-deformed
and welded tubular profile. The steel quality was S355J2H, SIIB, -40 C. The root of the
weld is ground and the seam is also ultrasonic-controlled during tube manufacture. The
mechanical properties of the tube are: Rp0.2 474 MPa, Rm 530 MPa, A5 24% and
charpy V test averaged 245 J at -40 C.
As a special request, the outside corner radius of the square tube was controlled. The
radius should be according to EN 10219 for square tubular products 2.5xT, when the
thickness T is between 6 to 10 mm. The measured radius was 27 mm. This value was
controlled due to the fact that this radius has a remarkable effect on the stress concentration that, in turn, has an effect on the load bearing capacity of the insert.
The straightness of the square tubes was controlled before welding with a gauge and
with a string wire. After assemblage the steel rack form and straightness was again controlled. The openings were gauged successfully with the 156 mm gauge. The bottom
end flatness and perpendicularity was controlled. The result was acceptable and the allowable inaccuracy was 2 mm. The square profiles were welded together equidistantly
in 6 section of the length.
After ·assemblage the steel rack was first cleaned in picking tank (in hydrochloric acid
for 4 to 10 hours) and then, after flushing, drying and transportation to foundry, it was
still sand blasted (inside and outside) to avoid all oxidation.
The construction of the mould can be seen in the photographs in Appendix 1. This time
the square tubes of the rack were filled with furfuran sand to avoid bending of the flat
walls of the tubes inwards. In the first test casting of an insert in Finland, in 1998, sand
without any binding agent was used. Then excessive bending was gained.
5
4
CASTING
Casting of the insert took place on March 10 in 2003. The casting temperature of the
iron melt was a little increased. The aim of this was that the bond between cast iron and
the steel insert surface was known to be weak and this modification in the procedure
was tried to get a better bond between the surfaces. The melt temperature was now
1360-70 °C instead of the normal temperature of 1310 °C. The time needed for filling
the mould was 85 sec.
The casting process is inadequately documented. The detailed control documentation is
required according to KTSO 11 specification, paragraph 4. The documentation should
include recording of melting parameters such like tapping temperature, temperature for
Mg addition and inoculation, time elapsed between Mg addition and pouring, pouring
temperature and time. In addition, samples for chemical analysis is advised to be taken
after Mg treatment.
Figure 1. Beginning of casting the insert.
.------------------------------------------------------------------ --
-
6
5
CLEANING AND CUTTING THE CAST
After cooling down the cast was cleaned. In this phase there were some indications of
problems detected in the top part of the cast. First, some eccentricity of the top part of
the cast was identified. The eccentricity was some 7 mm. This was caused due to the
weak supporting of the steel rack. However, this 7 mm eccentricity could be compensated in the machining phase because of radial working margin of 10 mm. Secondly,
there was seen some damage of the square tubes on the top part of the cast. The top end
of the tubes had been either melted or seriously deformed. Moreover, the melt iron had
penetrated partly into the square tubes.
This kind of damage revealed that the feed box had been installed in angular respect in
wrong position. The 12 openings of the feed box directed mistakenly the running iron
melt partly against the top end of the sand filled square tubes and not direct to the falling openings between the steel rack and the cylindrical outer surface of the mould. This
was an error in assemblage of the mould. The angular positioning error can be afterwards verified even in the photographs in Appendix 1.
In spite of melt iron intrusion into the rack tubes the cast could be cleaned and the
openings could be emptied with one exception. However, after cutting off the excess
part from the top part of the cast (some 600-700 mm) the openings were in good shape
and condition.
Figure 2. Cutting off the excess part at the top of the insert.
7
6
DIMENSIONAL CONTROL BEFORE MACHINING
The shape and size was controlled after cleaning and cutting off the excessive top part
of the cast. Also the bottom end was cut by the large band saw of JyvaskyHi foundry.
Length was acceptable. The cast had intentional excessive length in both ends. The outside diameter had a working margin of 20 mm. As discussed above, the top part of the
cast had some 7 mm eccentricity, but this could be acceptably handled by the working
margin.
After cleaning and cutting the cast openings were gauged according to the requirements
of the specification with 152 mm gauge. The gauge travelled through all the 12 openings without being stuck.
In general, the dimensional tests of the cast were passed.
Figure 3. Dimensional control of the insert openings.
8
7
MACHINING
The rough turning of the cast was made in the Metso Paper workshop in Jyvaskyla. The
turning lathe is usually used for machining of paper mill cylinders. The cast was machined direct to final main dimensions.
Any other details were not machined.
Figure 4. The insert after machining.
9
8
DIMENSIONAL CONTROL AFTER MACHINING
After machining in the turning lathe the dimensions of the cast were controlled. The diameter was in tolerance D949 +0.5/-0.0 mm and the length 4573 +0.0/-0.5 mm. The top
end of the cast was centralised before machining according to the square openings and
thus the outer surface eccentricity was totally vanished during machining. The integral
bottom thickness was 60 mm.
10
9
MATERIAL TESTING
In addition to the normal cast-on material samples, there was a plan to make destructive
sampling also from the cast body itself. After machining and dimensional control the
insert was cut into pieces according to Figure 5.
200 200
/
......
,..... /....
500
....
,.
/
....
I
I
I
I
I
I
I
I
I
.,.
....
....
~
,.
....
!
I
I
I
I
I
I
I
44
200
200
,,.
,.
i
i
i
#2
#3
#5
#1
i
i
i
i
i
....,:,.
2286
2287
, ....
4573
.,.
.....
,....
,......
Figure 5. Cutting of the insert to slices. Slices # 1, #2 and #4 were used for materials
testing, slice #3 is sent to Posiva for demonstration purpose and slice #5 is sent to SKB
for NDT-testing exercise. Top end is to the right. The two larger remaining pieces are
left at the foundry, so far.
The standard type testing was made according to requirements of EN 1563. The results
are as shown in Table 1 and 2. Material samples were from cast-on test pieces at both
top and bottom. No hardness test was made.
Table 1. Chemical composition of the cast material.
Chemical composition (%)
c
Si
Mn
s
p
Mg
3.65
2.22
0.25
0.010
0.02
0.04
11
Table 2. Mechanical properties according to EN 1563 Type 11 test. Two tests were made
from cast-on samples at top and bottom.
Mechanical properties
Yield
strength
MPa
Tensile
strength
MPa
Elongation
%
Measured (top)
238 I 232
320 I 319
6.5 I 8.9
Measured (bottom)
235 I 233
325 I 323
10 I 9.7
240
370
11
Standard requirement
A microstructure test (metallography) was made from the top and bottom cast-on samples, too. The result is in Table 3. The result is far from the specified value. The microscope views of the corresponding locations are shown in Figs. 6 and 7.
Further material testing was made for samples taken from the cast body itself. Samples
were taken from slices # 1, #2 and #4 in Figure 1. In each slice one sample was taken
tangentially from the circumference and the other from the centre transversely. The result of the mechanical testing is given in Table 4.
The non-conformity of the metallographic and mechanical testing results is selfevidently coupled together. The cast process has failed due to some errors in the performance. And the investigation of the reason for the failure is difficult, because the
documentation of the casting process control is inadequate.
Table 3. Microstructure properties according to metallographic test. Two tests were
made from samples at top and bottom. Samples were cast fixed with the cast body.
Microstructure
Graphite form and share
Size
Matrix
Measured
(top)
IV+VI- 40%, ill -60%
4-5
Ferr 98%,
Perl2%
Measured
(bottom)
IV+VI - 30%, Ill -70%
5
Ferr 99%,
Peril%
Specification
requirement
KTSOll
V+VI ~80%, I-ID 0%
~100 noduleslmm 2
12
57915 no 1 Hiekuvia kappaleesta irroitetuista koesauvoista. 48Xsuurennos
A1
IV-VI-30%,111-700/o
koko 4-5
Ferr. 98%, perl. 2%
~--- K1
IV-VI-300fo,lll-70%
koko6
Ferr.1'00%
Y1
IV-Vl-20°A~ 111-80%
koko 5
Ferr. 99%, perL
1~o
Figure 6. Microscope view of the ground cast surface. Samples are from the centre of
the insert at bottom (AI), middle (Kl) and top (Yl).
13
S7915 no 1 Hiekuvia kappaleesta irroitetuista. koesauvo·i sta. 48XsuuA!nnos
A2
:JV-VI-25°/o-,111-75% •
koko 5
Ferr. 100%
, _ _ _ K2
IV-VI-30%,111-70%
koko 4
Ferr. 100%
~..--
_ ___, Y2
IV-VI-30%,tll-70%
koko 4
Ferr. 100%
Figure 7. Microscope view of the ground cast surface. Samples are from the circumferential edge area of the insert at bottom (A2), middle (K2) and top (Y2).
14
Table 4. Mechanical testing result from slices #1, #2 and #4 in Figure 1. Samples are
taken from the destructed cast body.
Yield
strength
MP a
Tensile
strength
MPa
Elongation
Top, at the edge
245
319
4.6
Top, at centre
234
318
6.5
Middle, at edge
235
321
9.6
Middle, at centre
235
314
4.9
Bottom, at edge
236
328
9.4
Bottom, at centre
236
313
4.6
Reference value for
EN-GJS-400-15U, t=60-200 mm
240
370
11
%
The interface between the square tubes and the cast were shown to be loose. When the
excessive top part of the cast was sawed off the tubes went in some 1 mm from the cutting surface. This tells that the square tubes had a high residual tensile stress and that the
tensile stress caused a shear-out phenomenon close to the cutting section. In addition,
when the tensile stress test specimen were made of 200 mm long slices of the cast, some
pieces of the square tubes were totally loosened from the cast body, see Figure 8. below.
Figure 8. Making the tensile test samples from the 200 mm long slices of the cast.
15
Ultrasonic testing was made for the block between slices #3 and #5 in Figure 4. Some
indications were detected in 6 locations. The locations are given in Table 5 and Fig. 9.
Table 5. Indications from ultrasonic testing.
Indication
number
Size of area
(mm)
Area of indication (cm2)
Depth from
outer surface
(mm)
Distance from
top surface
(mm)
1
20 X 80
16
23-32
2990
2
20 X 90
18
25-33
3150
3
20 X 70
14
29
3130
4
30 X 40
12
25
3250
5
30 X 70
21
25
3350
6
60 X 90
54
25
3140
DD
r---D_D-t----D-~_~p
\,DD DD/
DD
Figure 9. The angular locations of the ultrasonic indications when seen from the top
end of the insert.
16
After making the ultrasonic testing the indication number 6 was opened. The indication
was built up of porosity. The size of the pores was 0.5 - 2.0 mm. Figure 10 shows the
porosity of the opened indication.
Figure 10. Porosity of the indication number 6 of the insert.
17
10
SUMMARY
The result of the insert cast trial fulfilled all the dimensional and shape requirements but
the material mechanical properties and metallurgical structure of the cast material did
not satisfy the requirements of the specification.
The measured tensile strength, ultimate strength and elongation at rupture were lower
than specified. The reason for this was revealed in the metallurgical investigation of the
cast material. The nodulizing of the graphite was not occurred during the casting process according to the requirements.
The Metso J yvaskyHi foundry personnel suppose that the reason for the failure is that
the liquid iron was poured to wrong locations in the mould. The iron should go direct
into the empty space between the square tubes of the rack inside the mould. However,
the openings of the sink were erroneously directing the iron partly into the square tubes
filled with wet furfuran sand. The hot iron put the sand "boil" and the steam has caused
the metallurgical problem. Also the "boiling" of the sand has thrown some sand into the
mould and thus causing some pores detected by ultrasonic testing.
18
Appendix 1: Photographs from manufacturing phases
Steel profile cassette
in assembly.
Construction of the
mould in the
moulding pit
(below).
19
Pouring gate construction and assembly (above).
Casting takes some
85 seconds.
~ -20
As cast condition,
top of the insert
Bottom of the insert, the four legs
are cut off.
Cutting off the top
part of the cast
billet (below).
21
As machined, top
side and bottom
(above).
Dimensional
control of the
openings.
A 200 mm slice
cut for material
testing.
~- ----------------
RESEARCH REPORT
I PRO 117045/03
1 6.11.2003
--------------------------------------~~-
TEST MANUFACTURE OF A CANISTER
INSERT
Author:
Heikki Raiko
Publicity:
Confidential
VTT PROCESSES
Research organisation and address
Customer
VTT Processes, Nuclear Energy
P.O. Box 1608
FIN-02044 VTT, FINLAND
Posiva Oy
Project manager
Contact person
Heikki Raiko
Nils-Christian Wikstrom ~
Diary code (VTT)
Order reference
PRO 1/7045/03
9516/03/NW
Project title and reference code
Report identification & Pages
Date
Kapselointitekniikkaan liittyva tutkimus- ja kehitystoiminta
13KAPSTEKN03, C3SU00163
PRO 1/7045/03
17 p. + App. 4 p.
6.11.2003
27160 OLKILUOTO
'7o.r k.. .
2.e ,
tr. '2.-0 17 :I
/
Report title and author( s)
Raiko, Heikki
Summary
This report describes the insert-manufacturing test of a disposal canister for spent nuclear fuel that
was made by Metso Paper Oy, JyvaskyHi Foundry, in 2003 on contract for Posiva Oy.
The test manufacture was a part of the co-operation development programme of encapsulation
technology between SKB AB and Posiva Oy.
Insert casting was specified according to the current manufacturing specifications of SKB. The
canister insert was of BWR-type with integral bottom. This was the first trial manufacture of this
type of insert in Finland and, in total, the second test manufacture of insert by Metso Paper.
The result fulfilled all the requirements but the material mechanical properties and metallurgical
structure of the cast material. The measured tensile strength, ultimate strength and elongation at
rupture were lower than specified. The reason for this was revealed in the metallurgical investigation of the cast material. The nodulizing of the graphite was not occurred during the casting process according to the requirements.
Distribution
Posiva 2 ex.
Pr~j,;t m11nageYJl
Publicity
Confidential
;J
crw,«~ (.KG4~~
Heikki Raiko
Reviewed and approved by
A it<-
Arto Muurinen
Group manager
~~
Sepg
uori
Research manager
The use of the name of the Technical Research Centre of Finland (VTT) in advertising or publication in part of
this report is only permissible by written authorisation from the Technical Research Centre of Finland
Abstract
This report describes the insert-manufacturing test of a disposal canister for spent nuclear fuel that was made by Metso Paper Oy, JyvaskyHi Foundry, in 2003 on contract
for Posiva Oy.
The test manufacture was a part of the co-operation development programme of encapsulation technology between SKB AB and Posiva Oy.
The result fulfilled all the requirements but the material mechanical properties and metallurgical structure of the cast material. The measured tensile strength, ultimate strength
and elongation at rupture were lower than specified. The reason for this was revealed in
the metallurgical investigation of the cast material. The nodulizing of the graphite was
not occurred during the casting process according to the requirements.
Keywords: canister insert, nodular cast iron, disposal canister for spent nuclear fuel
LOPPUSIJOITUSKAPSELIN SISAOSAN KOEV ALMISTUS
Tiivistelma
Tassa raportissa kuvataan kaytetyn ydinpolttoaineen loppusijoituskapselin stsaosan
valmistuskoe, joka suoritettiin Metso Paper Oy:n J yvaskylan valimossa vuonna 2003
Posiva Oy:n toimeksiannosta.
Koevalmistus oli osa SKB AB:n ja Posiva Oy:n valista kapselointiteknologiaa koskevaa
yhteistyossa tehtavaa teknologian kehitysohjelmaa.
Sisaosan valun laatutavoitteet oli maaritelty SKB:n senhetkisten valmistusspesifikaatioiden mukaisesti. Kanisterin sisaosa oli BWR-polttoaineelle tarkoitettua tyyppia ja siina oli kiintea pohjapaaty. Valmistuskoe oli talla sisaosatyypilla ensimmainen Suomessa
suoritettu ja kaiken kaikkiaan Metso Paperin suorittamana valukokeena toinen.
Valmistuskokeen tulokset tayttivat vaatimukset kaikilta muilta osin paitsi valumateriaalin mekaanisten ominaisuuksien ja metallurgisen rakenteen osalta. Mitatut vetolujuuden,
murtolujuuden ja murtovenyman arvot jaivat vaatimusten alapuolelle. Syy tahan paljastui valumateriaalin metallografisessa tutkimuksessa. Grafiitin palloutuminen ei ollut
tapahtunut valussa vaatimusten mukaisesti.
Avainsanat: kanisterin sisaosa, pallografiittirauta, kaytetyn ydinpolttoaineen loppusijoituskanisteri.
1
CONTENTS
Abstract
Tii vistelma
1
IN"TRODUCTION .................................................................................................. 2
2
IN"SERT SPECIFICATION ..................................................................................... 3
3
DESCRIPTION OF PREPARIN"G THE CASSETTE AND MOULD
MANUFACTURE .................................................................................................. 4
4
CASTIN"G ................................................................................................................ 5
5
CLEANIN"G AND CUTTIN"G THE CAST ............................................................ 6
6
DIMENSIONAL CONTROL BEFORE MACHINING ........................................ 7
7
MACIIININ"G ......................................................................................................... 8
8
DIMENSIONAL CONTROL AFfER MACHINING ........................................... 9
9
MATERIAL TESTIN"G ........................................................................................ 10
10
SUMMARY .......................................................................................................... 17
APPENDIX 1: Photographs from manufacturing phases ............................................... 18
2
1
INTRODUCTION
This report describes the insert-manufacturing test of a disposal canister for spent nuclear fuel that was made by Metso Paper Oy, JyvaskyHi Foundry, in 2003 on contract
for Posi va Oy.
The test manufacture was a part of the co-operation development programme of encapsulation technology between SKB AB and Posiva Oy. The SKB identification for this
insert is 127.
r---------------------------------------------------- ----- -3
2
INSERT SPECIFICATION
The insert test manufacture was ordered according to following specifications.
The steel profile cassette used as the central core of the cast is given in drawing SKB
00004-121, revision E. The cast iron insert as pre-machined is given in drawing SKB
00004-122, revision D. The test gauge for the dimensional test of the openings is given
in drawing SKB TEST 00002, revision B.
The steel profile cassette assembly and the details of the fixing attachments can be
modified according to engineering expertise. Also, the structure of the dimensional test
gauge can be modified for better practicability.
Technical specification for profiles in the steel section cassette is given in SKB technical specification no KTS022, revision 0. The specification for the steel section cassette
is given in KTS021, revision 2. And finally the specification for the nodular cast iron
EN1563 insert is given in KTS011, revision 2.
Procedure instructions are given for "requirements on 1) quality plan, 2) manufacturing
and inspection plan", for "identification of canister components", for "control of inspection, measuring and test equipment" in documents: KT 0704, revision 3, KT 0705,
revision 2, KT 0801, revision 1, KT 1102, revision 2, and KT 1103, revision 2.
In addition, due to first test manufacture of this type of insert in the foundry, an additional destructive material testing was specified according to specification KTS011,
paragraph 6.2 for three sections of the cast; top, middle and bottom.
4
3
DESCRIPTION OF PREPARING THE CASSETTE AND MOULD MANUFACTURE
The steel profile cassette was manufactured at a subcontractor to the JyvaskyHi foundry.
Therefore, a detailed stepwise procedure plan was made to assure the demanding manufacture and control sequence including detailed documentation.
The square steel tubes used for the cassette was made of Rautaruukki cold-deformed
and welded tubular profile. The steel quality was S355J2H, SI/B, -40 C. The root of the
weld is ground and the seam is also ultrasonic-controlled during tube manufacture. The
mechanical properties of the tube are: Rp0.2 474 MPa, Rm 530 MPa, A5 24% and
charpy V test averaged 245 J at -40 C.
As a special request, the outside corner radius of the square tube was controlled. The
radius should be according to EN 10219 for square tubular products 2.5xT, when the
thickness T is between 6 to 10 mm. The measured radius was 27 mm. This value was
controlled due to the fact that this radius has a remarkable effect on the stress concentration that, in turn, has an effect on the load bearing capacity of the insert.
The straightness of the square tubes was controlled before welding with a gauge and
with a string wire. After assemblage the steel rack form and straightness was again controlled. The openings were gauged successfully with the 156 mm gauge. The bottom
end flatness and perpendicularity was controlled. The result was acceptable and the allowable inaccuracy was 2 mm. The square profiles were welded together equidistantly
in 6 section of the length.
After assemblage the steel rack was first cleaned in picking tank (in hydrochloric acid
for 4 to 10 hours) and then, after flushing, drying and transportation to foundry, it was
still sand blasted (inside and outside) to avoid all oxidation.
The construction of the mould can be seen in the photographs in Appendix 1. This time
the square tubes of the rack were filled with furfuran sand to avoid bending of the flat
walls of the tubes inwards. In the first test casting of an insert in Finland, in 1998, sand
without any binding agent was used. Then excessive bending was gained.
r - - - - - - - -- - -- - - - - -- - -- -- - -
-
-
5
4
CASTING
Casting of the insert took place on March 10 in 2003. The casting temperature of the
iron melt was a little increased. The aim of this was that the bond between cast iron and
the steel insert surface was known to be weak and this modification in the procedure
was tried to get a better bond between the surfaces. The melt temperature was now
1360-70 °C instead of the normal temperature of 1310 °C. The time needed for filling
the mould was 85 sec.
The casting process is inadequately documented. The detailed control documentation is
required according to KTSO 11 specification, paragraph 4. The documentation should
include recording of melting parameters such like tapping temperature, temperature for
Mg addition and inoculation, time elapsed between Mg addition and pouring, pouring
temperature and time. In addition, samples for chemical analysis is advised to be taken
after Mg treatment.
Figure 1. Beginning of casting the insert.
6
5
CLEANING AND CUTTING THE CAST
After cooling down the cast was cleaned. In this phase there were some indications of
problems detected in the top part of the cast. First, some eccentricity of the top part of
the cast was identified. The eccentricity was some 7 mm. This was caused due to the
weak supporting of the steel rack. However, this 7 mm eccentricity could be compensated in the machining phase because of radial working margin of 10 mm. Secondly,
there was seen some damage of the square tubes on the top part of the cast. The top end
of the tubes had been either melted or seriously deformed. Moreover, the melt iron had
penetrated partly into the square tubes.
This kind of damage revealed that the feed box had been installed in angular respect in
wrong position. The 12 openings of the feed box directed mistakenly the running iron
melt partly against the top end of the sand filled square tubes and not direct to the falling openings between the steel rack and the cylindrical outer surface of the mould. This
was an error in assemblage of the mould. The angular positioning error can be afterwards verified even in the photographs in Appendix 1.
In spite of melt iron intrusion into the rack tubes the cast could be cleaned and the
openings could be emptied with one exception. However, after cutting off the excess
part from the top part of the cast (some 600-700 mm) the openings were in good shape
and condition.
Figure 2. Cutting off the excess part at the top of the insert.
7
6
DIMENSIONAL CONTROL BEFORE MACHINING
The shape and size was controlled after cleaning and cutting off the excessive top part
of the cast. Also the bottom end was cut by the large band saw of JyvaskyHi foundry.
Length was acceptable. The cast had intentional excessive length in both ends. The outside diameter had a working margin of 20 mm. As discussed above, the top part of the
cast had some 7 mm eccentricity, but this could be acceptably handled by the working
margin.
After cleaning and cutting the cast openings were gauged according to the requirements
of the specification with 152 mm gauge. The gauge travelled through all the 12 openings without being stuck.
In general, the dimensional tests of the cast were passed.
Figure 3. Dimensional control of the insert openings.
8
7
MACHINING
The rough turning of the cast was made in the Metso Paper workshop in JyvaskyHi. The
turning lathe is usually used for machining of paper mill cylinders. The cast was machined direct to final main dimensions.
Any other details were not machined.
Figure 4. The insert after machining.
9
8
DIMENSIONAL CONTROL AFTER MACHINING
After machining in the turning lathe the dimensions of the cast were controlled. The diameter was in tolerance D949 +0.5/-0.0 mm and the length 4573 +0.0/-0.5 mm. The top
end of the cast was centralised before machining according to the square openings and
thus the outer surface eccentricity was totally vanished during machining. The integral
bottom thickness was 60 mm.
10
9
MATERIAL TESTING
In addition to the normal cast-on material samples, there was a plan to make destructive
sampling also from the cast body itself. After machining and dimensional control the
insert was cut into pieces according to Figure 5.
200 200
.....
....
,..... .....
....
500
.....
....
,.....
200
200
,...............
.... ,
~
!
I
I
I
I
I
I
I
~4
I
I
I
I
I
I
I
I
I
.....
i
i
i
#2
#3
#5
#1
i
i
i
i
i
2286
2287
, :......
, "'
"'
4573
.....
....
.....
.....
.....
.....
Figure 5. Cutting of the insert to slices. Slices # 1, #2 and #4 were used for materials
testing, slice #3 is sent to Posiva for demonstration purpose and slice #5 is sent to SKB
for NDT-testing exercise. Top end is to the right. The two larger remaining pieces are
left at the foundry, so far.
The standard type testing was made according to requirements of EN 1563. The results
are as shown in Table 1 and 2. Material samples were from cast-on test pieces at both
top and bottom. No hardness test was made.
Table 1. Chemical composition of the cast material.
Chemical composition (%)
c
Si
Mn
s
p
Mg
3.65
2.22
0.25
0.010
0.02
0.04
11
Table 2. Mechanical properties according to EN 1563 Type 11 test. Two tests were made
from cast-on samples at top and bottom.
Yield
strength
MPa
Tensile
strength
MPa
Elongation
%
Measured (top)
238 I 232
320 I 319
6.5 I 8.9
Measured (bottom)
235 I 233
325 I 323
10 I 9.7
240
370
11
Standard requirement
A microstructure test (metallography) was made from the top and bottom cast-on samples, too. The result is in Table 3. The result is far from the specified value. The microscope views of the corresponding locations are shown in Figs. 6 and 7.
Further material testing was made for samples taken from the cast body itself. Samples
were taken from slices #1, #2 and #4 in Figure 1. In each slice one sample was taken
tangentially from the circumference and the other from the centre transversely. The result of the mechanical testing is given in Table 4.
Table 3. Microstructure properties according to metallographic test. Two tests were
made from samples at top and bottom. Samples were cast fixed with the cast body.
Microstructure
Graphite form and share
Size
Matrix
Measured
(top)
IV+VI- 40%, Ill -60%
4-5
Ferr98%,
Perl2%
Measured
(bottom)
IV+VI- 30%, lli -70%
5
Ferr 99%,
Peril%
Specification
requirement
KTSOll
V+VI ~80%, I-ID 0%
~100 noduleslmm 2
12
57915 no 1 Hiekuvia kappaleesta irroitetuista koesauvoista. 48Xsuurennos
A1
IV-VI-30%,111-70'0fo
koko 4--5
Ferr. 98%, perl. 2%
'--.-6 K1
IV-VI-300fo,lll-70%
koko 6
Ferr. 10()4/o
Y1
IV-VI-200fo,lll~'-'80%
' koko 5
Ferr. 99%, pert 10fo
Figure 6. Microscope view of the ground cast surface. Samples are from the centre of
the insert at bottom (AI), middle (Kl) and top (Yl).
13
S7915 no 1 Hiekuvia kappaleesta irroitetuista koesauvoista. 48Xsuurennos
A2
IV-VI-25°4,111~75%
.
koko 5
Ferr. 100%
t - - - K2
IV-VI-30%,111-70%
koko4
Ferr. 100%
~...-_
____. Y2
IV-VI-30°k,lllr-70%
koko4
.F err.100%
Figure 7. Microscope view of the ground cast surface. Samples are from the circumferential edge area of the insert at bottom (A2), middle (K2) and top (Y2).
.-----------------------------------------------
- - - ---
--
14
Table 4. Mechanical testing result from slices #1, #2 and #4 in Figure 1. Samples are
taken from the destructed cast body.
Yield
strength
MPa
Tensile
strength
MPa
Elongation
Top, at the edge
245
319
4.6
Top, at centre
234
318
6.5
Middle, at edge
235
321
9.6
Middle, at centre
235
314
4.9
Bottom, at edge
236
328
9.4
Bottom, at centre
236
313
4.6
Reference value for
EN-GJS-400-15U, t=60-200 mm
240
370
11
%
The interface between the square tubes and the cast were shown to be loose. When the
excessive top part of the cast was sawed off the tubes went in some 1 mm from the cutting surface. This tells that the square tubes had a high residual tensile stress and that the
tensile stress caused a shear-out phenomenon close to the cutting section. In addition,
when the tensile stress test specimen were made of 200 mm long slices of the cast, some
pieces of the square tubes were totally loosened from the cast body, see Figure 8. below.
Figure 8. Making the tensile test samples from the 200 mm long slices of the cast.
15
Ultrasonic testing was made for the block between slices #3 and #5 in Figure 4. Some
indications were detected in 6 locations. The locations are given in Table 5 and Fig. 9.
Table 5. Indications from ultrasonic testing.
Indication
number
Size of area
(mm)
Area of indication (cm2)
Depth from
outer surface
(mm)
Distance from
top surface
(mm)
1
20 X 80
16
23-32
2990
2
20 X 90
18
25-33
3150
3
20 X 70
14
29
3130
4
30 X 40
12
25
3250
5
30 X 70
21
25
3350
6
60 X 90
54
25
3140
DD
1----D_D-t----D_[g]_-~
\DD DD 1
DD
------
~-Vi" n :o 5
I
Figure 9. The angular locations of the ultrasonic indications when seen from the top
end of the insert.
16
After making the ultrasonic testing the indication number 6 was opened. The indication
was built up of porosity. The size of the pores was 0.5 - 2.0 mm. Figure 10 shows the
porosity of the opened indication.
Figure 10. Porosity of the indication number 6 of the insert.
r-------------------------------------------------------------------- - --
- -- --
17
10
SUMMARY
The result of the insert cast trial fulfilled all the dimensional and shape requirements but
the material mechanical properties and metallurgical structure of the cast material did
not satisfy the requirements of the specification.
The measured tensile strength, ultimate strength and elongation at rupture were lower
than specified. The reason for this was revealed in the metallurgical investigation of the
cast material. The nodulizing of the graphite was not occurred during the casting process according to the requirements.
The Metso J yvaskyHi foundry personnel suppose that the reason for the failure is that
the liquid iron was poured to wrong locations in the mould. The iron should go direct
into the empty space between the square tubes of the rack inside the mould. However,
the openings of the sink were erroneously directing the iron partly into the square tubes
filled with wet furfuran sand. The hot iron put the sand "boil" and the steam has caused
the metallurgical problem. Also the "boiling" of the sand has thrown some sand into the
mould and thus causing some pores detected by ultrasonic testing.
18
Appendix 1: Photographs from manufacturing phases
Steel profile cassette
in assembly.
Construction of the
mould in the
moulding pit
(below).
19
Pouring gate construction and assembly (above).
Casting takes some
85 seconds.
20
•
As cast condition,
top of the insert
Bottom of the insert, the four legs
are cut off.
Cutting off the top
part of the cast
billet (below).
~----------------------------------------
-- --
- ---
21
•
As machined, top
side and bottom
(above).
Dimensional
control of the
openings.
A 200 mm slice
cut for material
testing.

Test Manufacture of a Canister Insert

Transcription

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