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Uwaba, Tomoyuki; ;
JNC TN9400 2000-006, 50 Pages, 1999/11
JNC-TN9400-2000-006.pdf:2.17MB
In the fast reactor the swelling of the fuel cladding occur due to the irradiation. Under the irradiation, the temperature gradient of the cladding through the direction of its thickness causes the swelling gradient and this will cause the secondary stress. In this study, we analyzed this secondary stress using the finite element model of the irradiation induced deformation of the cladding by FINAS code. The result of this analysis is summarized as follows. (1)The secondary stress is mainly caused by the gradient of the incubation period of the swelling, The secondary stress becomes very small at the end of irradiation due to the relieving of the stress by the irradiation creep deformation accelerated by the swelling. (2)The calculated maximum stress including the secondary stress under the irradiation is compared with the design value of the ultimate tensile strength for PNC316 for trial. The calculated value are lower than the design value. (3)The effect of the swelling accelerated by the stress is analyzed using the correlation between the swelling and the stress. The result shows that the increasing of the secondary stress due to the acceleration of the swelling is very small because the irradiation creep deformation relieves the stress more effectively by the acceleration of the irradiation creep rate due to the swelling.
*; *; Tanai, Kenji
JNC TN8400 99-048, 85 Pages, 1999/11
This paper reports the results of design analysis and trial manufacturing of full-scale titanium-carbon steel composite overpacks. The overpack is one of the key components of the engineered barrier system, hence, it is necessary to confirm the applicability of current technique in their manufacture. The required thickness was calculated according to mechanical resistance analysis, based on models used in current nuclear facilities. The Adequacy of the calculated dimensions was confirmed by finite-element methods. To investigate the necessity of a radiation shielding function of the overpack, the irradiation from vitrified waste has been calculated. As a result, it was shown that shielding on handling and transport equipment is a more reasonable and practical approach than to increase thickness of overpack to attain a self-shielding capability. After the above investigation, trial manufacturing of full-scale model of titanium-carbon steel composite overpack has been carried out. For corrosion-resistant material, ASTM Grade-2 titanium was selected. The titanium layer was bonded individually to a cylindrical shell and flat cover plates (top and bottom) made of carbon steel. For the cylindrical shell portion, a cylindrically formed titanium layer was fitted to the inner carbon steel vessel by shrinkage. For the flat cover plates (top and bottom), titanium plate material was coated by explosive bonding. Electron beam welding and gas metal arc welding were combined to weld of the cover plates to the body. No significant failure was evident from inspections of the fabrication process, and the applicability of current technology for manufacturing titanium-carbon steel composite overpack was confirmed. Future research and development items regarding titanium-carbon steel composite overpacks are also discussed.
*; *; Tanai, Kenji
JNC TN8400 99-047, 54 Pages, 1999/11
This paper reports on the design process for a carbon-steel overpack as a key component in the engineered barrier system of a deep geological repository described in the 2nd progress report. The results of the research and development regarding design requirements, configuration, manufacturing and inspection of overpack are also described. The concept of a composite overpack composed of two different materials is also considered. First, the design requirements for an overpack and presume environmental and design conditions for a repository are provided. For a candidate material of carbon steel overpack, forging material is selected considering enough experience of using this material in nuclear power boilers and other components. Second, loading conditions after emplacement in a repository are set and the pressure-resistant thickness of overpack is calculated. The corrosion thickness to achieve an assigned 1000 year life time and the required thickness to prevent radiolysis of ground water which might enhance corrosion rate are also determined. As aresult, the total required thickness of a carbon-steel overpack is conservatively estimated to 190 mm. This is a reduction of about 30% from the previous estimate provided in the 1st Progress Report. Additional items that must be considered in manufacturring and operating overpacks (i.e. sealing of vitrified waste, examination of main body and sealing welding, mechanism of handling) are evaluated on the basis of current technology, specific future data needs are identified. With respect to the concept of composite overpack (i.e., an outer vessel to provide corrosion-allowance or corrosion-resistant performance and an inner vessel to provide pressure-resistance), the differences in design concepts between the carbon-steel overpack and such composite overpacks are analyzed. Future data needs and analytical capabilities with respect to overpacks are also summarized.
Suzuki, Masahide;
JAERI-Research 94-038, 23 Pages, 1994/11
JAERI-Research-94-038.pdf:0.87MB
no abstracts in English