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*; *; 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.
Koi, Mamoru
PNC TN9410 90-105, 163 Pages, 1990/07
Fatigue and creep crack growth data of SUS304 stainless steel, 2.25Cr-1Mo steel and Mod.9Cr-1Mo steel, which were accumulated in PNC in last several years, were treated as a data base. Average trend equations of crack growth rate were proposed and also statistical analysis was carried out. Finite Elements analysis of center cracked tensioned plate was performed and simplified prediction method of modified J-integral J'(C 
) was developed. 0btained results are summerized as follows: (1)In all tested materials, fatigue crack growth rate and creep crack growth rate were successfully represented using cyclic J-integral range 
J and modified J-integral J', respectivery. (2)In all tested materials, meaningful difference of crack growth rate could not be detected between hot rolled plate and forged material, and also between base metal and welded material. (3)Averaged trend equations of fatigue crack growth rate and creep crack growth rate of all tested materials were proposed on the basis of power low with cyclic J-integral range and modified J-integral, respectively. (4)Assuming that the coefficient and exponent of the above power low obey joint normal distribution, statistical analysis of crack growth rate was carried out and relationship between variance and J, J' were obtained. (5)Simplified method was developed to predict modified J-integral of center cracked tensioned plate. Prediction results show good agreement with experimental results, and this fact suggests that J-integral evaluation method of 3-dimensional surface crack, which has been developed in PNC, has good prediction accuracy.
