Fracture mechanics approach for failure mode analysis in CABRI and NSRR RIA tests

CABRI及びNSRR実験における破損モード解析のための破壊力学的アプローチ

Georgenthum, V.*; 杉山 智之 ; 宇田川 豊  ; 更田 豊志; Desquines, J.*

Georgenthum, V.*; Sugiyama, Tomoyuki; Udagawa, Yutaka; Fuketa, Toyoshi; Desquines, J.*

An analysis based on an Elastic Plastic Fracture Mechanics approach has been derived to understand the cladding failure conditions during the Pellet Cladding Mechanical Interaction phase of an RIA transient. The impact of incipient cracks at the cladding periphery has been evaluated through the calculation of J-integral. The J-integral is evaluated in a module coupled with the SCANAIR code and compared to the critical value of the J-integral deduced from the fracture toughness of Zircaloy. The clad metallography on CABRI and NSRR tested fuel rods provided the depth of brittle zone, i.e., the length of incipient crack. This analysis shows the J-integral can be used both in the elastic and elasto-plastic ranges to predict the failure occurrences. The study also points out that due to the strong dependence of hydride solubility with temperature, the conditions are more severe in the NSRR room temperature than in the CABRI or the Pressurized Water Reactor temperature.