- Email: [email protected]
Containment integrity evaluation of MSF-type cask for interim storage and transport of PWR spent fuel
International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
Contents lists available at ScienceDirect
International Journal of Pressure Vessels and Piping journal homepage: www.elsevier.com/locate/ijpvp
Containment integrity evaluation of MSF-type cask for interim storage and transport of PWR spent fuel Yoshiyuki Saito a, *, Junichi Kishimoto a, Toshihiro Matsuoka a, Hiroki Tamaki a, Akio Kitada b a b
Nuclear Energy Systems, Mitsubishi Heavy Industries Ltd, 1-1-1 Wadasaki-cho, Hyogo-ku Kobe 652-8585, Japan Takasago Research & Development Center, Mitsubishi Heavy Industries Ltd, 2-1-1 Shinhama Arai-cho, Takasago 676-8686, Japan
a b s t r a c t Keywords: Spent fuel Interim storage Transport Dual purpose cask MSF-21P Full scale drop test
Many spent fuel storage pools in nuclear plant facilities are now reaching their full capacity in Japan. As a solution of this issue, Mitsubishi Heavy Industries, ltd. (MHI) has developed a high integrity dual purpose cask for interim storage and transport of PWR spent fuel. As for the dual purpose cask, the conformity with the requirements for leak-tightness during transport specified in IAEA Safety Standards (Safety Requirements No. TS-R-1) has to be verified by drop tests and/or numerical simulations. A Full-scale drop test is a valid and feasible way for demonstrating a containment performance because it is difficult to scale down a closure system, especially the dimensions and characteristics of the metallic O-rings attached to the lids, according to the scaling law. Therefore, MHI conducted full-scale drop tests and demonstrated the conformity with the leak-tightness requirements. The closure system of the MSF-21P cask has been designed on the basis of the full-scale drop test results and its containment integrity has been verified by dynamic Finite Element (FE) analyses based on the full-scale drop test results. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction Many spent fuel storage pools in nuclear plant facilities are now reaching their full capacity, and the need for interim storage is growing rapidly in Japan. One of the most feasible options is dry storage in metallic casks, notably dual-purpose metallic casks which can be used for interim storage and transport of spent nuclear fuel before storage and even after storage without reloading. Dual purpose casks shall be designed to meet the requirements for both the storage regulation and the transport regulation [1]. Mitsubishi Heavy Industries, ltd. (MHI) developed a resin material for neutron shielding [2] and boron containing aluminum alloy for the basket [3] to achieve long-term stability in storage. MHI also conducted full-scale and 1/2.5 scale drop tests on the MSF-type cask from 2004 to 2005 [4] and shock absorber compression tests [5] with the cooperation of BAM (Bundesanstalt für Materialforschung und-prüfung) to demonstrate the containment performance during transport. MHI has analyzed and verified the shock absorber performance and the response of the closure system equipped with metallic O-rings. Based on these technologies and the full-scale drop test results, MHI has developed a high-
* Corresponding author. Tel.: þ81 78 672 4915; fax: þ81 78 672 3427. E-mail address: [email protected] (Y. Saito). 0308-0161/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijpvp.2013.10.007
integrity dual-purpose metallic cask, MSF-21P, the containment integrity of which can be preserved under hypothetical accidental drop conditions of transport.
2. Structural features of MSF-21P cask 2.1. Outline of MSF-21P cask The MSF-21P cask has been developed as a high-integrity dualpurpose cask which can accommodate 21 PWR spent fuel assemblies. Schematic views of the transport and storage configurations of the MSF-21P cask are shown in Fig. 1. Typical specifications of the MSF-21P cask are shown in Table 1. The main components and the materials of the MSF-21P cask are shown in Table 2. The cask body comprises mainly the body shell, outer shell, neutron shielding, heat conductor plates and trunnions. The cylindrical part and base part of the body shell made of forged low alloy steel function as a primary gamma shield. Heat conductor plates made of copper are longitudinally welded along the body shell and the outer shell. MHI developed neutron shielding material (MREXÒ) is inserted into the space between the body shell and outer shell. Trunnions are attached for lifting and lashing the cask. Inside the cask cavity, a basket made of MHI developed boron containing aluminum alloy, comprising 21 cells to house 21 PWR
34
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
Fig. 1. Configurations of the MSF-21P cask.
spent fuel assemblies, is inserted. The basket has two functions, that is, criticality prevention and decay heat dissipation. A primary lid and a secondary lid made of forged low alloy steel equipped with metallic O-rings are bolted to the body flange. During transport, a tertiary lid made of stainless steel equipped with elastomer O-rings is bolted to the top of the body flange. The lids constitute the main part of the closure system. A detailed description of the closure system is provided in Chapter 3.1. During transport, a pair of wooden shock absorbers covered with stainless steel plates is attached to both ends of the cask. The
purpose of the shock absorbers is to reduce the impact force on the cask and its content in the event of an accidental drop. 2.2. Advanced original materials 2.2.1. Epoxy resin (MREXÒ) A neutron shielding material “MREXÒ” of high-temperature stability for long-term services was developed (see Fig. 2).
Table 1 Specifications of the MSF-21P cask (design sample).
Contents
Cask
Items
Specifications
Fuel type Number of fuel Weight (tons) Burnup (GWd/MTU) U-235 initial enrichment (%) Cooling period (years) Thermal power (kW) Dimensions (m)
PWR 21 20.8 48 (Max.) 4.1 15 13.9 F2.5 5.1a F3.6 6.8b 113a 131b
Total weight (tons) a b
Storage configuration. Transport configuration.
Table 2 Components and materials (design sample). Main components Cask body - Body shell - Outer shell - Neutron shielding - Heat conductor - Trunnions Lids - Primary lid - Secondary lid - Tertiary lid - O-rings Basket Shock absorbers - Frame/cover - Infill
Materials Low alloy steel Carbon steel Epoxy resin (MREXÒ) Copper Stainless steel Low alloy steel Low alloy steel Stainless steel Aluminum/Inconel/Inconel Elastomer Boron containing aluminum alloya Stainless steel Wood (Balsa, Red cedar, Oak)
a Registered in ASME code case N-673 [6] and JSME code case FA-CC-005 (BCA6N01SS-T1) [7].
Fig. 2. Production of MREXÒ.
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
35
Shock absorber compression tests Load-displacement characteristics (RT/high temp.)
Fig. 3. Basket assembly (design example).
The material is made of epoxy based resin and filler for refractory. The material mixing and filling facility was also developed to reduce manufacturing costs and improve quality control. In order to confirm the extent of damage of MREXÒ during long-term storage, various in-house performance tests such as heating tests, neutron irradiation tests and fire resistant tests was conducted [2].
Shock absorber FE analysis model [Verification]
Drop tests (full-scale, 1/2.5 scale)
Decelerations Strains
Leakage rates (full-scale)
Drop test FE analysis model [Verification]
Drop test FE analysis of MSF-21P cask [Containment integrity of closure system] Fig. 5. Containment integrity evaluation procedure.
2.2.2. Boron containing aluminum alloy Boron containing aluminum alloys manufactured with the powder metallurgy process were developed as basket materials. The aluminum alloys have high boron content, homogeneous boron distribution, higher toughness and sufficient strength for long-term services. In order to evaluate the effect of temperature and irradiation during long-term storage, in-house tests including creep tests, thermal aging tests and neutron irradiation tests were conducted [3]. One of the alloys has been registered as ASME code case N-673 [6] and JSME code case FA-CC-005 (BC-A6N01SS-T1) [7]. The alloys can be formed into various shapes of basket assembly, such as rectangular hollow plates, by hot extrusion. An assembly of rectangular hollow plates is shown in Fig. 3 as an example.
space between the lids during storage. The sealing performance for long-term services is ensured by metallic O-rings attached to the lids. During transport before and after long-term storage, a tertiary lid equipped with elastomer O-rings is bolted to the top of the body flange. The secondary lid and the tertiary lid play the role of a double containment boundary during transport. In case of leakage of the primary lid during storage, the MSF-21P cask can be transported safely. The full-scale and 1/2.5 scale drop test model have a double closure lid system with metallic O-rings as shown in Fig. 4b. The primary lid and secondary lid made of forged low alloy steel are bolted to the body flange. 3.2. Evaluation procedure
3. Development of closure system 3.1. Outline of closure system The closure system of the MSF-21P cask, developed and designed on the basis of the full-scale and 1/2.5 scale drop test results of the MSF-type cask is shown in Fig. 4a. During storage, the primary lid and the secondary lid equipped with metallic O-rings are bolted to the body flange. The primary lid and the cask body form a containment boundary. Leakage of the lids can be detected by continuous monitoring of pressure variation in the
During transport, the closure system shall ensure the containment integrity through their double boundary function even under hypothetical accidental conditions. MHI has evaluated the containment integrity of the MSF-21P cask according to the following procedure (see Fig. 5). (1) Shock absorber compression tests Static compression tests were conducted to determine the loaddisplacement characteristics and temperature dependency of the
Tertiary lid (for transport)
Secondary lid
Secondary lid
Elastomer O-rings Primary lid Primary lid Metallic O-rings Metallic O-rings
a. MSF - 21P cask (Transport condition)
b. D rop test model
Fig. 4. Comparison of the closure system.
36
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41 Table 3 Weights and dimensions of drop test models. Items
Full-scale model
1/2.5 scale model
Content Number of fuel Weight of content (tons) Total cask weight (tons) Dimensions (m)
Dummy fuel 69 25.7 113a/127b F2.5 5.3a F3.1 6.8b
1.7 7.2a/8.0b F1.0 2.1a F1.2 2.7b
a b
Without shock absorbers. With shock absorbers.
the closure system of the MSF-21P cask has been evaluated by comparing the analysis results of the MSF-21P cask with those of the full-scale model. 3.3. Benchmark test (1) e shock absorber compression tests [5] Fig. 6. Shock absorber compression tests.
shock absorber as a component. The load-displacement characteristics of the shock absorber as a component are important because the deformation behavior of the wood is strongly influenced by the constraint conditions of the wood infill. (2) Drop tests on full-scale model and 1/2.5 scale model Drop tests on the full-scale model were conducted to demonstrate the containment and structural integrity of the closure system. The demonstration of the containment integrity on a full-scale model is very important, because the dimensions and characteristics of the metallic O-rings do not follow the scaling law. Drop tests on the 1/2.5 scale model were also conducted to confirm the structural integrity of the closure system. (3) Definition and verification of a drop test FE analysis model A dynamic Finite Element (FE) analysis model for the drop tests was defined and verified based on the drop test results and the shock absorber compression test results.
A semi-circular type 1/2.5 scale shock absorber model (See Fig. 6) was used for the compression tests. The tests were conducted at room temperature and at high temperature (average temperature of 100 C). Fig. 7 shows a comparison of the load-displacement characteristics obtained from the tests between room temperature and high temperature. These results indicate that the load-displacement characteristic of the component, as a whole, at high temperature corresponds to 53 5% of that at room temperature. The compression properties and temperature dependency of the component as a whole obtained from the tests are used for the design of shock absorbers for the MSF-21P cask. 3.4. Benchmark test (2) e drop tests on full-scale model and 1/2.5 scale model [4] 3.4.1. Drop test models The weights and dimensions of the drop test models used are shown in Table 3 and Fig. 8. The test models were manufactured under the supervision of third-party certifiers. In order to analyze the behaviors of the lids, lid bolts and body flange, approximately
(4) MSF-21P cask containment integrity evaluation A dynamic FE analysis model of the MSF-21P cask was defined based on the drop test analysis model. The containment integrity of
Fig. 7. Comparison of load-displacement characteristics between room temperature and high temperature (100 C).
Fig. 8. Dimensions of the drop test models.
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
37
Fig. 9. Drop tests on full-scale and 1/2.5 scale model.
60 strain gauges were attached to the closure system. Approximately 10 accelerators were also attached to the drop test models to evaluate the overall behavior of the models during drops. 3.4.2. Drop test sequences According to the IAEA regulation [1], the specimen shall drop onto the target so as to suffer maximum damage in respect of the safety features to be tested. 13 drop tests (full-scale: 5 tests, 1/2.5 scale: 8 tests) were conducted (see Fig. 9). In order to consider the cumulative effects of pre-damage due to 0.3 m drop, the height of the drop was set as 9.3 m. The main purpose of the full-scale drop tests was to demonstrate the containment integrity. Slap down followed by 1 m puncture drops and vertical drop, which were considered as more
severe drop conditions for the closure system, were included in the drop tests on the full-scale model. The inclined angle of the slap down was set as 10 , which gives the most severe impact force on the closure system than any other angles based on a prior evaluation. Also drop tests on a 1/2.5 scale model were conducted to compare the experimental results with those of the full-scale model [8] and to confirm the structural integrity of the closure system under the other conditions i.e., corner drop, horizontal drop and puncture.
Table 4 Leakage ratesa before/after drop test sequences with full-scale model. No.
Conditions
Primary lid Before
1 2 3 4-1 4-2
9.3 m slap down 1 m punctureb 9.3 m vertical 0.3 m slap down 9.0 m slap downc
Secondary lid After
11
<1 10 <1 1011 1.0 108 2.5 1011 1.0 1011
Before 11
<1 10 2.0 1011 3.9 106 1.0 1011 <1 1011
After 9
7.4 10 1.6 106 2.0 1011 1.5 1011 <1 1011
1.6 106 7.8 107 1.7 1011 <1 1011 3.0 107
a
Unit: Pa m3/s. 1 m puncture was conducted following 9.3 m slap down without change of metallic O-ring. c 9.0 m slap down was conducted following 0.3 m slap down without change of metallic O-ring. b
Fig. 10. Drop test analysis models (sectional view).
38
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
The increase of the primary lid leakage rate following a 9.3 m vertical drop is mainly caused by the lid opening due to plastic deformation of the sealing area of the lids. Therefore, strains on the lids and lid bolts are also important parameters for the containment integrity evaluation. Although the following two drop attitudes could also be critical to the containment integrity, the impact force exerted on the closure system decreased due to design features of the upper shock absorber.
20 Exp. (RT) Analysis Load (MN)
15
10
5
(1) Vertical drop onto a puncture bar from a height of 1 m should be considered as a more severe drop condition when the puncture bar approaches the small valve cover area of the secondary lid. (2) 9.3 m corner drop should be considered as a more severe drop condition because a large impact force is applied on a small corner area of the secondary lid.
0 0
30
60 90 120 150 Displacement (mm)
180
Fig. 11. Comparison of load-displacement characteristics (tested at room temperature).
3.5. Definition and verification of drop test FE analysis model Dynamic FE drop test analyses with a full-scale model were performed using LS-DYNA code [9]. The drop test analysis model is shown in Fig. 10, which includes the body shell with neutron shielding, outer shell, lids, bolts, basket, and dummy fuel assemblies. The dummy fuel assemblies were modeled as 69 individual rigid bodies. A gap between the content and the cask body at the time of the drop (i.e., delayed internal impact of the content) was taken into account. The shock absorbers verified by the shock absorber compression tests were also modeled. The loaddisplacement characteristics obtained from the analysis results agree well with those of the experimental results as shown in Fig. 11. In order to simulate the deformation behavior of the closure system, an elasto-plastic model with actual mechanical properties was used for the analyses. Furthermore, a strain rate dependency of the strength of the wood infill and steel structure was considered in the analysis model.
200
200
150
150
100
100
Deceleration (G)
Deceleration (G)
3.4.3. Drop test results In order to verify the conformity with the requirements of leaktightness of the lids, helium leakage tests were performed. Table 4 shows the leakage rates before and after full-scale drop tests. All the leakage rates of secondary lid and primary lid were well below the leakage rate of 1 104 Pa m3/s corresponding to the criteria based on the IAEA regulation. The increase of secondary lid leakage rate following a 9.3 m/9 m slap down test is mainly caused by damage of the O-rings attached to the lids due to the relative displacements of the lids and deformation of the sealing area of the lids and body flange in the impact region. Therefore, strains on the lids periphery and body flange in the impact region are important parameters for the containment integrity evaluation. There is no increase in the leakage rates following a 1 m puncture test. It is assumed that the thick inner plates of the shock absorber absorb the impact of the puncture bar.
50 0 -50
a. Top side
-100
Exp.(A211_y) Analysis(A211_y)
A211
-150
Primary impact
Secondary impact
50 0 -50 -100
b. Middle
-150
A321
Exp.(A321_y) Analysis(A321_y)
-200
-200 75
100
125 150 Time (ms)
175
200
75
100
125 150 Time (ms)
175
200
(Top)
Deceleration (G)
150 100
A211
50 0 -50
c. Bottom side
-100
A331
-150
Exp.(A331_y) Analysis(A331_y)
Y Z
-200 75
100
125 150 Time (ms)
175
200
Fig. 12. Comparison of decelerations (9.3 m slap down).
(Bottom) A321
A331
200
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
4000
Strain (µ)
0 -1000
0 -500 Exp.(E211_y) Analysis(E211_y)
-1500
-4000
-2000
75
4000
100
125 150 Time (ms)
175
200
75
100
125 150 Time (ms)
175
200
b. Body flange (inner)
3000
E363
2000
Strain (µ)
500
-1000
Exp.(E353_z) Analysis(E353_z)
-3000
E211
1000
1000
-2000
c. Secondary lid
1500
E353
2000
Strain (µ)
2000
a. Body flange (outer)
3000
39
E211
1000 0 -1000 -2000
Exp.(E363_z) Analysis(E363_z)
-3000
E363
Y Z
E353
-4000 75
100
125 150 Time (ms)
175
200
Fig. 13. Comparison of strains (9.3 m slap down).
The analysis results of the slap down test are shown as an example. Comparisons of the decelerations of the cask body and of the strains on the closure system between the analytical and experimental results are shown in Fig. 12 and Fig. 13, respectively. These figures show that deceleration time histories and strain time histories of the analytical results agree well with those of the experimental results between a primary impact and a secondary impact.
4000
2000
2000
1000
1000
Strain (µ)
Strain (µ)
b. Body flange (inner)
3000
0 -1000 -2000
2LP 3LP
0 -1000 -2000
MSF-21P (BF1_z)
-3000
Drop Test Model (BF1_z)
Y
MSF-21P (BF2_z) Drop Test Model (BF2_z)
-3000
-4000
BF2 Z
BF1 [MSF-21P cask]
-4000
0
20
40
60 80 Time (msec)
100
0
120
20
40
60 80 Time (msec)
100
120
2000
500 400 300 200 100 0 -100 -200 -300 -400 -500
c. Secondary lid (periphery)
d. Tertiary lid (periphery)
1500 1000
Strain (µ)
Strain (µ)
3.6.1. MSF-21P cask closure system design Leakage rates following a 9.3 m/9 m slap down test and a 9.3 m vertical drop test using a full-scale model increased by an order of magnitude of two to four compared to those before the tests as shown in Table 4. In consideration of the uncertainty related to the integrity of metallic O-rings after long-term storage, the closure
4000
a. Body flange (outer)
3000
3.6. MSF-21P cask containment integrity evaluation
1LP 2LP
500 0 -500
MSF-21P (2LP_y) Drop Test Model (1LP_y)
Z
MSF-21P (3LP_y) Drop Test Model (2LP_y)
-1500
20
40
60 80 Time (msec)
100
120
0
20
40
60 80 Time (msec)
BF1 [Drop test model]
-2000 0
BF2
Y
-1000
100
120
Fig. 14. Comparison of strains between MSF-21P cask and full-scale drop test model in a 9.3 m slap down test.
40
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
1500
2000 MSF-21P (2LC_y) Drop Test Model (1LC_y)
1500
MSF-21P (3LC_y) Drop Test Model (2LC_y)
1000
500
Strain (µ)
Strain (µ)
1000
0 -500
500
2ry lid bolts 2LC
0 -500
-1000
Z
-1000
-1500
a. Secondary lid (center)
-2000
3LC Y
b. Tertiary lid (center)
[MSF-21P cask]
-1500
0
10
20 30 Time (sec) 3500
40
50
0
10
20 30 Time (sec)
50
1ry lid bolts
2500 1500 Strain (µ)
40
1LC
500 -500
c. Secondary lid bolts
-1500
Z
MSF-21P (2ry Lid Bolts_z) Drop Test Model (1ry Lid Bolts_z)
-2500 -3500 0
10
20 30 Time (msec)
40
2LC Y [Drop test model]
50
Fig. 15. Comparison of strains between MSF-21P cask and full-scale drop test model in a 9.3 m vertical drop test.
system of the MSF-21P cask should be designed to limit the increase in leakage rate between before and after accidental conditions during transport. The closure system is designed on the basis of the drop test measurement results by comparison of the important parameters such as strains of the body flange and lids. Furthermore, important features of the shock absorbers of the drop test models (i.e. arrangement of wood material and inner steel structure) were taken into account in the shock absorber design. 3.6.2. Analysis model The MSF-21P cask analysis model was established on the basis of the verified drop test analysis model as shown in Chapter 3.5. The spent fuel assemblies were modeled individually with actual mechanical properties. Furthermore, delayed internal impact of the content was taken into account. The mechanical properties specified in the material standards were used for the cask. The inclined angle of the slap down was set as 10 , which gives the most severe impact force on the closure system than any other angles. The analyses were conducted at a maximum design temperature with a thermal load of 13.9 kW. The strength degradation of the woodfilled shock absorbers due to temperature increase was taken into account. 3.6.3. Analysis results The structural integrity of the closure system of the MSF-21P cask under accidental conditions of transport was demonstrated by dynamic FE analyses, which showed that the MSF-21P cask can provide a higher closure system integrity than the full-scale model. The analysis results of the 9.3 m slap down and 9.3 m vertical drop tests, which are considered as severe drop conditions as regards the closure system, are shown below. Comparison of the important parameters such as strains in the impact area of the body flange and lids between the MSF-21P cask and the full-scale drop test analysis results are shown in Fig. 14 (Slap down) and Fig. 15 (Vertical). These analysis results confirm the structural integrity of the closure system of the MSF-21P cask
because the strains are smaller than those applied to the drop test model. It can therefore be considered that the increase in leakage rates is smaller for the MSF-21P cask than for the full scale model. Strains of the primary lid of the MSF-21P cask are also smaller than those applied to the drop test model although it does not function as the containment boundary under the transport conditions. Furthermore, no plastic strains occurred in the secondary lid and the tertiary lid including the sealing area of the metallic or elastomer O-rings and lid bolts of the MSF-21P cask. 4. Conclusions MHI has developed the high-integrity dual purpose cask, MSF21P, for interim storage and transport of PWR spent fuel. The cask is designed not only for long-term storage but also for transport before and after storage. Its containment integrity has been verified by dynamic FE analysis established on the basis of the full-scale drop test results, and shows that its closure system has a high robustness even under hypothetical accidental drop conditions of transport. Acknowledgment MHI thanks BAM for giving MHI the opportunity to present pictures taken on the BAM TTS (Test site Technical Safety) in Germany. Statements in this paper concerning test results reflect MHI’s point of view only; MHI’s statements do not represent the official BAM point of view. References [1] Regulations for the safe transport of radioactive material. IAEA safety standards series No. TS-R-1. 2009 Edition. [2] Ichihashi T, Ishiko D, Ogawa A, Morishima M. Verification tests of neutron shielding materials and shielding assessment. Proceedings of the 15th International Symposium on the Packaging and Transportation of Radioactive materials 2007.
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41 [3] Maeguchi T, Kamiwaki Y, Ishiko D, Yamamoto T. Development and reliability verification of aluminum alloys for basket of transport and storage cask for spent nuclear fuel. Proc. Proceedings of the 15th International Symposium on the Packaging and Transportation of Radioactive materials 2007. [4] Tamaki H, Kimura T, Hode S, Kishimoto J, Yamamoto T. Structural integrity of MSF-57BG Transport and storage cask based on full-scale and 1/2.5-scale drop test results. Proceedings of the 15th International Symposium on the Packaging and Transportation of Radioactive materials 2007. [5] Kishimoto J, Kitada A, Nishizaki C, Saito Y. Dependency of temperature on wooden materials’ mechanical property and effect of impact energy absorption of shock absorbers. Proceedings of the 15th International Symposium on the Packaging and Transportation of Radioactive materials 2007.
41
[6] ASME boiler and pressure vessel code sectionⅢ division 1 case N-673, Boron containing powder metallurgy aluminum alloy for storage and transportation of spent nuclear fuel; 2003. [7] JSME S FA1, Codes for construction of spent nuclear fuel storage facilities -rules on transport/storage packagings for spent nuclear fuel- case FA-CC-005; 2007. [8] Quercetti T, Müller K, Schubert S. Comparison of experimental results from drop testing of spent fuel package design using full scale prototype model and reduced scale model. Packaging Transp Storage Security Radioactive Mater 2008;19(4):197e202. [9] LS-DYNA Keyword user’s manual version 971, Livermore software technology corporation; 2007.
Contents lists available at ScienceDirect
International Journal of Pressure Vessels and Piping journal homepage: www.elsevier.com/locate/ijpvp
Containment integrity evaluation of MSF-type cask for interim storage and transport of PWR spent fuel Yoshiyuki Saito a, *, Junichi Kishimoto a, Toshihiro Matsuoka a, Hiroki Tamaki a, Akio Kitada b a b
Nuclear Energy Systems, Mitsubishi Heavy Industries Ltd, 1-1-1 Wadasaki-cho, Hyogo-ku Kobe 652-8585, Japan Takasago Research & Development Center, Mitsubishi Heavy Industries Ltd, 2-1-1 Shinhama Arai-cho, Takasago 676-8686, Japan
a b s t r a c t Keywords: Spent fuel Interim storage Transport Dual purpose cask MSF-21P Full scale drop test
Many spent fuel storage pools in nuclear plant facilities are now reaching their full capacity in Japan. As a solution of this issue, Mitsubishi Heavy Industries, ltd. (MHI) has developed a high integrity dual purpose cask for interim storage and transport of PWR spent fuel. As for the dual purpose cask, the conformity with the requirements for leak-tightness during transport specified in IAEA Safety Standards (Safety Requirements No. TS-R-1) has to be verified by drop tests and/or numerical simulations. A Full-scale drop test is a valid and feasible way for demonstrating a containment performance because it is difficult to scale down a closure system, especially the dimensions and characteristics of the metallic O-rings attached to the lids, according to the scaling law. Therefore, MHI conducted full-scale drop tests and demonstrated the conformity with the leak-tightness requirements. The closure system of the MSF-21P cask has been designed on the basis of the full-scale drop test results and its containment integrity has been verified by dynamic Finite Element (FE) analyses based on the full-scale drop test results. Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction Many spent fuel storage pools in nuclear plant facilities are now reaching their full capacity, and the need for interim storage is growing rapidly in Japan. One of the most feasible options is dry storage in metallic casks, notably dual-purpose metallic casks which can be used for interim storage and transport of spent nuclear fuel before storage and even after storage without reloading. Dual purpose casks shall be designed to meet the requirements for both the storage regulation and the transport regulation [1]. Mitsubishi Heavy Industries, ltd. (MHI) developed a resin material for neutron shielding [2] and boron containing aluminum alloy for the basket [3] to achieve long-term stability in storage. MHI also conducted full-scale and 1/2.5 scale drop tests on the MSF-type cask from 2004 to 2005 [4] and shock absorber compression tests [5] with the cooperation of BAM (Bundesanstalt für Materialforschung und-prüfung) to demonstrate the containment performance during transport. MHI has analyzed and verified the shock absorber performance and the response of the closure system equipped with metallic O-rings. Based on these technologies and the full-scale drop test results, MHI has developed a high-
* Corresponding author. Tel.: þ81 78 672 4915; fax: þ81 78 672 3427. E-mail address: [email protected] (Y. Saito). 0308-0161/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijpvp.2013.10.007
integrity dual-purpose metallic cask, MSF-21P, the containment integrity of which can be preserved under hypothetical accidental drop conditions of transport.
2. Structural features of MSF-21P cask 2.1. Outline of MSF-21P cask The MSF-21P cask has been developed as a high-integrity dualpurpose cask which can accommodate 21 PWR spent fuel assemblies. Schematic views of the transport and storage configurations of the MSF-21P cask are shown in Fig. 1. Typical specifications of the MSF-21P cask are shown in Table 1. The main components and the materials of the MSF-21P cask are shown in Table 2. The cask body comprises mainly the body shell, outer shell, neutron shielding, heat conductor plates and trunnions. The cylindrical part and base part of the body shell made of forged low alloy steel function as a primary gamma shield. Heat conductor plates made of copper are longitudinally welded along the body shell and the outer shell. MHI developed neutron shielding material (MREXÒ) is inserted into the space between the body shell and outer shell. Trunnions are attached for lifting and lashing the cask. Inside the cask cavity, a basket made of MHI developed boron containing aluminum alloy, comprising 21 cells to house 21 PWR
34
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
Fig. 1. Configurations of the MSF-21P cask.
spent fuel assemblies, is inserted. The basket has two functions, that is, criticality prevention and decay heat dissipation. A primary lid and a secondary lid made of forged low alloy steel equipped with metallic O-rings are bolted to the body flange. During transport, a tertiary lid made of stainless steel equipped with elastomer O-rings is bolted to the top of the body flange. The lids constitute the main part of the closure system. A detailed description of the closure system is provided in Chapter 3.1. During transport, a pair of wooden shock absorbers covered with stainless steel plates is attached to both ends of the cask. The
purpose of the shock absorbers is to reduce the impact force on the cask and its content in the event of an accidental drop. 2.2. Advanced original materials 2.2.1. Epoxy resin (MREXÒ) A neutron shielding material “MREXÒ” of high-temperature stability for long-term services was developed (see Fig. 2).
Table 1 Specifications of the MSF-21P cask (design sample).
Contents
Cask
Items
Specifications
Fuel type Number of fuel Weight (tons) Burnup (GWd/MTU) U-235 initial enrichment (%) Cooling period (years) Thermal power (kW) Dimensions (m)
PWR 21 20.8 48 (Max.) 4.1 15 13.9 F2.5 5.1a F3.6 6.8b 113a 131b
Total weight (tons) a b
Storage configuration. Transport configuration.
Table 2 Components and materials (design sample). Main components Cask body - Body shell - Outer shell - Neutron shielding - Heat conductor - Trunnions Lids - Primary lid - Secondary lid - Tertiary lid - O-rings Basket Shock absorbers - Frame/cover - Infill
Materials Low alloy steel Carbon steel Epoxy resin (MREXÒ) Copper Stainless steel Low alloy steel Low alloy steel Stainless steel Aluminum/Inconel/Inconel Elastomer Boron containing aluminum alloya Stainless steel Wood (Balsa, Red cedar, Oak)
a Registered in ASME code case N-673 [6] and JSME code case FA-CC-005 (BCA6N01SS-T1) [7].
Fig. 2. Production of MREXÒ.
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
35
Fig. 3. Basket assembly (design example).
The material is made of epoxy based resin and filler for refractory. The material mixing and filling facility was also developed to reduce manufacturing costs and improve quality control. In order to confirm the extent of damage of MREXÒ during long-term storage, various in-house performance tests such as heating tests, neutron irradiation tests and fire resistant tests was conducted [2].
Shock absorber FE analysis model [Verification]
Drop tests (full-scale, 1/2.5 scale)
Decelerations Strains
Leakage rates (full-scale)
Drop test FE analysis model [Verification]
Drop test FE analysis of MSF-21P cask [Containment integrity of closure system] Fig. 5. Containment integrity evaluation procedure.
2.2.2. Boron containing aluminum alloy Boron containing aluminum alloys manufactured with the powder metallurgy process were developed as basket materials. The aluminum alloys have high boron content, homogeneous boron distribution, higher toughness and sufficient strength for long-term services. In order to evaluate the effect of temperature and irradiation during long-term storage, in-house tests including creep tests, thermal aging tests and neutron irradiation tests were conducted [3]. One of the alloys has been registered as ASME code case N-673 [6] and JSME code case FA-CC-005 (BC-A6N01SS-T1) [7]. The alloys can be formed into various shapes of basket assembly, such as rectangular hollow plates, by hot extrusion. An assembly of rectangular hollow plates is shown in Fig. 3 as an example.
space between the lids during storage. The sealing performance for long-term services is ensured by metallic O-rings attached to the lids. During transport before and after long-term storage, a tertiary lid equipped with elastomer O-rings is bolted to the top of the body flange. The secondary lid and the tertiary lid play the role of a double containment boundary during transport. In case of leakage of the primary lid during storage, the MSF-21P cask can be transported safely. The full-scale and 1/2.5 scale drop test model have a double closure lid system with metallic O-rings as shown in Fig. 4b. The primary lid and secondary lid made of forged low alloy steel are bolted to the body flange. 3.2. Evaluation procedure
3. Development of closure system 3.1. Outline of closure system The closure system of the MSF-21P cask, developed and designed on the basis of the full-scale and 1/2.5 scale drop test results of the MSF-type cask is shown in Fig. 4a. During storage, the primary lid and the secondary lid equipped with metallic O-rings are bolted to the body flange. The primary lid and the cask body form a containment boundary. Leakage of the lids can be detected by continuous monitoring of pressure variation in the
During transport, the closure system shall ensure the containment integrity through their double boundary function even under hypothetical accidental conditions. MHI has evaluated the containment integrity of the MSF-21P cask according to the following procedure (see Fig. 5). (1) Shock absorber compression tests Static compression tests were conducted to determine the loaddisplacement characteristics and temperature dependency of the
Tertiary lid (for transport)
Secondary lid
Secondary lid
Elastomer O-rings Primary lid Primary lid Metallic O-rings Metallic O-rings
a. MSF - 21P cask (Transport condition)
b. D rop test model
Fig. 4. Comparison of the closure system.
36
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41 Table 3 Weights and dimensions of drop test models. Items
Full-scale model
1/2.5 scale model
Content Number of fuel Weight of content (tons) Total cask weight (tons) Dimensions (m)
Dummy fuel 69 25.7 113a/127b F2.5 5.3a F3.1 6.8b
1.7 7.2a/8.0b F1.0 2.1a F1.2 2.7b
a b
Without shock absorbers. With shock absorbers.
the closure system of the MSF-21P cask has been evaluated by comparing the analysis results of the MSF-21P cask with those of the full-scale model. 3.3. Benchmark test (1) e shock absorber compression tests [5] Fig. 6. Shock absorber compression tests.
shock absorber as a component. The load-displacement characteristics of the shock absorber as a component are important because the deformation behavior of the wood is strongly influenced by the constraint conditions of the wood infill. (2) Drop tests on full-scale model and 1/2.5 scale model Drop tests on the full-scale model were conducted to demonstrate the containment and structural integrity of the closure system. The demonstration of the containment integrity on a full-scale model is very important, because the dimensions and characteristics of the metallic O-rings do not follow the scaling law. Drop tests on the 1/2.5 scale model were also conducted to confirm the structural integrity of the closure system. (3) Definition and verification of a drop test FE analysis model A dynamic Finite Element (FE) analysis model for the drop tests was defined and verified based on the drop test results and the shock absorber compression test results.
A semi-circular type 1/2.5 scale shock absorber model (See Fig. 6) was used for the compression tests. The tests were conducted at room temperature and at high temperature (average temperature of 100 C). Fig. 7 shows a comparison of the load-displacement characteristics obtained from the tests between room temperature and high temperature. These results indicate that the load-displacement characteristic of the component, as a whole, at high temperature corresponds to 53 5% of that at room temperature. The compression properties and temperature dependency of the component as a whole obtained from the tests are used for the design of shock absorbers for the MSF-21P cask. 3.4. Benchmark test (2) e drop tests on full-scale model and 1/2.5 scale model [4] 3.4.1. Drop test models The weights and dimensions of the drop test models used are shown in Table 3 and Fig. 8. The test models were manufactured under the supervision of third-party certifiers. In order to analyze the behaviors of the lids, lid bolts and body flange, approximately
(4) MSF-21P cask containment integrity evaluation A dynamic FE analysis model of the MSF-21P cask was defined based on the drop test analysis model. The containment integrity of
Fig. 7. Comparison of load-displacement characteristics between room temperature and high temperature (100 C).
Fig. 8. Dimensions of the drop test models.
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
37
Fig. 9. Drop tests on full-scale and 1/2.5 scale model.
60 strain gauges were attached to the closure system. Approximately 10 accelerators were also attached to the drop test models to evaluate the overall behavior of the models during drops. 3.4.2. Drop test sequences According to the IAEA regulation [1], the specimen shall drop onto the target so as to suffer maximum damage in respect of the safety features to be tested. 13 drop tests (full-scale: 5 tests, 1/2.5 scale: 8 tests) were conducted (see Fig. 9). In order to consider the cumulative effects of pre-damage due to 0.3 m drop, the height of the drop was set as 9.3 m. The main purpose of the full-scale drop tests was to demonstrate the containment integrity. Slap down followed by 1 m puncture drops and vertical drop, which were considered as more
severe drop conditions for the closure system, were included in the drop tests on the full-scale model. The inclined angle of the slap down was set as 10 , which gives the most severe impact force on the closure system than any other angles based on a prior evaluation. Also drop tests on a 1/2.5 scale model were conducted to compare the experimental results with those of the full-scale model [8] and to confirm the structural integrity of the closure system under the other conditions i.e., corner drop, horizontal drop and puncture.
Table 4 Leakage ratesa before/after drop test sequences with full-scale model. No.
Conditions
Primary lid Before
1 2 3 4-1 4-2
9.3 m slap down 1 m punctureb 9.3 m vertical 0.3 m slap down 9.0 m slap downc
Secondary lid After
11
<1 10 <1 1011 1.0 108 2.5 1011 1.0 1011
Before 11
<1 10 2.0 1011 3.9 106 1.0 1011 <1 1011
After 9
7.4 10 1.6 106 2.0 1011 1.5 1011 <1 1011
1.6 106 7.8 107 1.7 1011 <1 1011 3.0 107
a
Unit: Pa m3/s. 1 m puncture was conducted following 9.3 m slap down without change of metallic O-ring. c 9.0 m slap down was conducted following 0.3 m slap down without change of metallic O-ring. b
Fig. 10. Drop test analysis models (sectional view).
38
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
The increase of the primary lid leakage rate following a 9.3 m vertical drop is mainly caused by the lid opening due to plastic deformation of the sealing area of the lids. Therefore, strains on the lids and lid bolts are also important parameters for the containment integrity evaluation. Although the following two drop attitudes could also be critical to the containment integrity, the impact force exerted on the closure system decreased due to design features of the upper shock absorber.
20 Exp. (RT) Analysis Load (MN)
15
10
5
(1) Vertical drop onto a puncture bar from a height of 1 m should be considered as a more severe drop condition when the puncture bar approaches the small valve cover area of the secondary lid. (2) 9.3 m corner drop should be considered as a more severe drop condition because a large impact force is applied on a small corner area of the secondary lid.
0 0
30
60 90 120 150 Displacement (mm)
180
Fig. 11. Comparison of load-displacement characteristics (tested at room temperature).
3.5. Definition and verification of drop test FE analysis model Dynamic FE drop test analyses with a full-scale model were performed using LS-DYNA code [9]. The drop test analysis model is shown in Fig. 10, which includes the body shell with neutron shielding, outer shell, lids, bolts, basket, and dummy fuel assemblies. The dummy fuel assemblies were modeled as 69 individual rigid bodies. A gap between the content and the cask body at the time of the drop (i.e., delayed internal impact of the content) was taken into account. The shock absorbers verified by the shock absorber compression tests were also modeled. The loaddisplacement characteristics obtained from the analysis results agree well with those of the experimental results as shown in Fig. 11. In order to simulate the deformation behavior of the closure system, an elasto-plastic model with actual mechanical properties was used for the analyses. Furthermore, a strain rate dependency of the strength of the wood infill and steel structure was considered in the analysis model.
200
200
150
150
100
100
Deceleration (G)
Deceleration (G)
3.4.3. Drop test results In order to verify the conformity with the requirements of leaktightness of the lids, helium leakage tests were performed. Table 4 shows the leakage rates before and after full-scale drop tests. All the leakage rates of secondary lid and primary lid were well below the leakage rate of 1 104 Pa m3/s corresponding to the criteria based on the IAEA regulation. The increase of secondary lid leakage rate following a 9.3 m/9 m slap down test is mainly caused by damage of the O-rings attached to the lids due to the relative displacements of the lids and deformation of the sealing area of the lids and body flange in the impact region. Therefore, strains on the lids periphery and body flange in the impact region are important parameters for the containment integrity evaluation. There is no increase in the leakage rates following a 1 m puncture test. It is assumed that the thick inner plates of the shock absorber absorb the impact of the puncture bar.
50 0 -50
a. Top side
-100
Exp.(A211_y) Analysis(A211_y)
A211
-150
Primary impact
Secondary impact
50 0 -50 -100
b. Middle
-150
A321
Exp.(A321_y) Analysis(A321_y)
-200
-200 75
100
125 150 Time (ms)
175
200
75
100
125 150 Time (ms)
175
200
(Top)
Deceleration (G)
150 100
A211
50 0 -50
c. Bottom side
-100
A331
-150
Exp.(A331_y) Analysis(A331_y)
Y Z
-200 75
100
125 150 Time (ms)
175
200
Fig. 12. Comparison of decelerations (9.3 m slap down).
(Bottom) A321
A331
200
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
4000
Strain (µ)
0 -1000
0 -500 Exp.(E211_y) Analysis(E211_y)
-1500
-4000
-2000
75
4000
100
125 150 Time (ms)
175
200
75
100
125 150 Time (ms)
175
200
b. Body flange (inner)
3000
E363
2000
Strain (µ)
500
-1000
Exp.(E353_z) Analysis(E353_z)
-3000
E211
1000
1000
-2000
c. Secondary lid
1500
E353
2000
Strain (µ)
2000
a. Body flange (outer)
3000
39
E211
1000 0 -1000 -2000
Exp.(E363_z) Analysis(E363_z)
-3000
E363
Y Z
E353
-4000 75
100
125 150 Time (ms)
175
200
Fig. 13. Comparison of strains (9.3 m slap down).
The analysis results of the slap down test are shown as an example. Comparisons of the decelerations of the cask body and of the strains on the closure system between the analytical and experimental results are shown in Fig. 12 and Fig. 13, respectively. These figures show that deceleration time histories and strain time histories of the analytical results agree well with those of the experimental results between a primary impact and a secondary impact.
4000
2000
2000
1000
1000
Strain (µ)
Strain (µ)
b. Body flange (inner)
3000
0 -1000 -2000
2LP 3LP
0 -1000 -2000
MSF-21P (BF1_z)
-3000
Drop Test Model (BF1_z)
Y
MSF-21P (BF2_z) Drop Test Model (BF2_z)
-3000
-4000
BF2 Z
BF1 [MSF-21P cask]
-4000
0
20
40
60 80 Time (msec)
100
0
120
20
40
60 80 Time (msec)
100
120
2000
500 400 300 200 100 0 -100 -200 -300 -400 -500
c. Secondary lid (periphery)
d. Tertiary lid (periphery)
1500 1000
Strain (µ)
Strain (µ)
3.6.1. MSF-21P cask closure system design Leakage rates following a 9.3 m/9 m slap down test and a 9.3 m vertical drop test using a full-scale model increased by an order of magnitude of two to four compared to those before the tests as shown in Table 4. In consideration of the uncertainty related to the integrity of metallic O-rings after long-term storage, the closure
4000
a. Body flange (outer)
3000
3.6. MSF-21P cask containment integrity evaluation
1LP 2LP
500 0 -500
MSF-21P (2LP_y) Drop Test Model (1LP_y)
Z
MSF-21P (3LP_y) Drop Test Model (2LP_y)
-1500
20
40
60 80 Time (msec)
100
120
0
20
40
60 80 Time (msec)
BF1 [Drop test model]
-2000 0
BF2
Y
-1000
100
120
Fig. 14. Comparison of strains between MSF-21P cask and full-scale drop test model in a 9.3 m slap down test.
40
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41
1500
2000 MSF-21P (2LC_y) Drop Test Model (1LC_y)
1500
MSF-21P (3LC_y) Drop Test Model (2LC_y)
1000
500
Strain (µ)
Strain (µ)
1000
0 -500
500
2ry lid bolts 2LC
0 -500
-1000
Z
-1000
-1500
a. Secondary lid (center)
-2000
3LC Y
b. Tertiary lid (center)
[MSF-21P cask]
-1500
0
10
20 30 Time (sec) 3500
40
50
0
10
20 30 Time (sec)
50
1ry lid bolts
2500 1500 Strain (µ)
40
1LC
500 -500
c. Secondary lid bolts
-1500
Z
MSF-21P (2ry Lid Bolts_z) Drop Test Model (1ry Lid Bolts_z)
-2500 -3500 0
10
20 30 Time (msec)
40
2LC Y [Drop test model]
50
Fig. 15. Comparison of strains between MSF-21P cask and full-scale drop test model in a 9.3 m vertical drop test.
system of the MSF-21P cask should be designed to limit the increase in leakage rate between before and after accidental conditions during transport. The closure system is designed on the basis of the drop test measurement results by comparison of the important parameters such as strains of the body flange and lids. Furthermore, important features of the shock absorbers of the drop test models (i.e. arrangement of wood material and inner steel structure) were taken into account in the shock absorber design. 3.6.2. Analysis model The MSF-21P cask analysis model was established on the basis of the verified drop test analysis model as shown in Chapter 3.5. The spent fuel assemblies were modeled individually with actual mechanical properties. Furthermore, delayed internal impact of the content was taken into account. The mechanical properties specified in the material standards were used for the cask. The inclined angle of the slap down was set as 10 , which gives the most severe impact force on the closure system than any other angles. The analyses were conducted at a maximum design temperature with a thermal load of 13.9 kW. The strength degradation of the woodfilled shock absorbers due to temperature increase was taken into account. 3.6.3. Analysis results The structural integrity of the closure system of the MSF-21P cask under accidental conditions of transport was demonstrated by dynamic FE analyses, which showed that the MSF-21P cask can provide a higher closure system integrity than the full-scale model. The analysis results of the 9.3 m slap down and 9.3 m vertical drop tests, which are considered as severe drop conditions as regards the closure system, are shown below. Comparison of the important parameters such as strains in the impact area of the body flange and lids between the MSF-21P cask and the full-scale drop test analysis results are shown in Fig. 14 (Slap down) and Fig. 15 (Vertical). These analysis results confirm the structural integrity of the closure system of the MSF-21P cask
because the strains are smaller than those applied to the drop test model. It can therefore be considered that the increase in leakage rates is smaller for the MSF-21P cask than for the full scale model. Strains of the primary lid of the MSF-21P cask are also smaller than those applied to the drop test model although it does not function as the containment boundary under the transport conditions. Furthermore, no plastic strains occurred in the secondary lid and the tertiary lid including the sealing area of the metallic or elastomer O-rings and lid bolts of the MSF-21P cask. 4. Conclusions MHI has developed the high-integrity dual purpose cask, MSF21P, for interim storage and transport of PWR spent fuel. The cask is designed not only for long-term storage but also for transport before and after storage. Its containment integrity has been verified by dynamic FE analysis established on the basis of the full-scale drop test results, and shows that its closure system has a high robustness even under hypothetical accidental drop conditions of transport. Acknowledgment MHI thanks BAM for giving MHI the opportunity to present pictures taken on the BAM TTS (Test site Technical Safety) in Germany. Statements in this paper concerning test results reflect MHI’s point of view only; MHI’s statements do not represent the official BAM point of view. References [1] Regulations for the safe transport of radioactive material. IAEA safety standards series No. TS-R-1. 2009 Edition. [2] Ichihashi T, Ishiko D, Ogawa A, Morishima M. Verification tests of neutron shielding materials and shielding assessment. Proceedings of the 15th International Symposium on the Packaging and Transportation of Radioactive materials 2007.
Y. Saito et al. / International Journal of Pressure Vessels and Piping 117-118 (2014) 33e41 [3] Maeguchi T, Kamiwaki Y, Ishiko D, Yamamoto T. Development and reliability verification of aluminum alloys for basket of transport and storage cask for spent nuclear fuel. Proc. Proceedings of the 15th International Symposium on the Packaging and Transportation of Radioactive materials 2007. [4] Tamaki H, Kimura T, Hode S, Kishimoto J, Yamamoto T. Structural integrity of MSF-57BG Transport and storage cask based on full-scale and 1/2.5-scale drop test results. Proceedings of the 15th International Symposium on the Packaging and Transportation of Radioactive materials 2007. [5] Kishimoto J, Kitada A, Nishizaki C, Saito Y. Dependency of temperature on wooden materials’ mechanical property and effect of impact energy absorption of shock absorbers. Proceedings of the 15th International Symposium on the Packaging and Transportation of Radioactive materials 2007.
41
[6] ASME boiler and pressure vessel code sectionⅢ division 1 case N-673, Boron containing powder metallurgy aluminum alloy for storage and transportation of spent nuclear fuel; 2003. [7] JSME S FA1, Codes for construction of spent nuclear fuel storage facilities -rules on transport/storage packagings for spent nuclear fuel- case FA-CC-005; 2007. [8] Quercetti T, Müller K, Schubert S. Comparison of experimental results from drop testing of spent fuel package design using full scale prototype model and reduced scale model. Packaging Transp Storage Security Radioactive Mater 2008;19(4):197e202. [9] LS-DYNA Keyword user’s manual version 971, Livermore software technology corporation; 2007.