Brittle Fracture Tests of Cask Materials for Transporting Radioactive Materials

Abstract

The IAEA Regulations for the Safe Transport of Radioactive Material stipulates that Type B(U) packages shall be designed for an ambient temperature range from −40°C to +38°C. Guidelines for the safe design of shipping packages against brittle fracture were provided by the IAEA TECDOC-717 in 1993. This report discusses the applicability of the actual method for brittle fracture assessment to Type B transport cask materials used in Japan. The necessity of brittle fracture assessment at low temperature was estimated for each material of Type B transport casks used in Japan and the applicability was investigated. Dynamic fracture toughness tests were conducted and K_Id (J_Id), and RT_NDT values of low Mn carbon steels (SA350 Gr. LFI Modify and SA516 Gr. 70 material used in Type B transport cask body) were obtained. All the obtained K_Id (J_Id) values were over the ASME K_IR curve. It was then confirmed that an easier and conventional RT_NDT-K_IR curve method prescribed in ASME Code Section III can be substituted for the dynamic fracture test method for low Mn carbon steels. Also, toughness data for bolt materials including 1.8Ni O.8Cr 0.3Mo Carbon steel and type 630 H stainless steel were obtained for reference. For bolt materials, it is clear that the brittle fracture assessment using K_ID (or J_Id) values is desirable considering the anisotropic feature of the material properties. Lastly, regarding the elastic-plastic problem, the fracture toughness study by CRIEPI using non-linear fracture mechanics should be utilised.