DEVELOPMENT AND DISCUSSION OF DESIGN CODE FOR BASKETS MADE OF ALUMINUM ALLOYS AND BORATED ALUMINUM ALLOYS FOR TRANSPORT/STORAGE PACKAGINGS

The Japan Society of Mechanical Engineers (JSME) established the Rules on Transport/Storage Packagings for Spent Fuel as a part of Codes for Construction of Spent Nuclear Fuel Storage Facilities in August, 2001. The Rules nominated only conventional steels as materials for the basket of packagings. On the other hand most of current designs proposed for transport/storage packaging in Japan adopt aluminum alloy or borated aluminum alloy as a material of the basket to enjoy merits of better heat conduction and component weight reduction. Therefore a material and design code for such basket has been anticipated eagerly. To meet this need the Subgroup on Spent Fuel Storage Facilities of the JSME started development of the rules on aluminum alloy basket in April, 2004. After two years of concentrated work by members of the Subgroup, a draft of the rule, which will be a part of proposed revision of the Rules on Transport/Storage Packagings, is at the final stage of approval process in the Committee. The proposed rules for aluminum alloy basket consist of the following three parts, (1) Requirements for the material of aluminum alloy for basket, (2) Requirements for the design of aluminum alloy basket, and (3) Guidelines for the application of aluminum alloy as a new material for the spent fuel transport/storage packaging basket. The design rules limit the creep strain during a design life up to 60 years not to exceed 0.4 %, though they allow to use the material in a temperature range of creep growth. While the allowable stress limits against long term loadings are set with creep effects in consideration, the limits against short term loadings such as package drop in the transport after the storage are not. 2 The guidelines address methods to establish allowable stress values with consideration of creep and over-aging (reversion) of age hardening aluminum alloys together with methods on testing the material and processing collected material data. In this paper details of the rules and major discussions on them within the JSME Committees are introduced.