Year
1992
File Attachment
1304.PDF1.61 MB
Abstract
From the viewpoint of economy, the nuclear spent fuel shipping or intermediate storage casks of ferritic nodular cast iron have attracted particular attention and have been developed. According to the IAEA regulations, type B(U) casks shall be designed for ambient temperature range from -40 to 3a·c. In addition, the structural integrity must be ensured against impact loading for a nine meter drop of casks. Unlike austenitic stainless steels, ferritic steels such as carbon steels and ferritic nodular cast irons are subject to inherent embrittlement at low temperature. Ductile-brittle transition temperature increases with increasing loading rate. Therefore, for maintaining the structural integrity of casks made of these ferritic steels, brittle or unstable fracture is an important consideration. It is reasonable to apply fracture mechanics analysis for the evaluation of fracture, and because of high loading rate the evaluation on the basis of dynamic fracture toughness is necessary. Toughness of ferritic nodular cast irons is low in comparison with austenitic stainless steels or carbon steels because of the large amount of graphite. Therefore, as to this material, it is necessary to ensure the sufficient toughness in the ductile fracture region (upper shelf region) to prevent ductile and unstable fracture and to clarify the effect of loading rate on brittle fracture. The objective of this study is to characterize the behavior of dynamic fracture toughness of a ferritic nodular cast iron and to evaluate this material as a material for casks.