The transportation and storage casks have to be designed by considering transport and handling accidents. IAEA safety standard[l] requires drop test using a scale model and demonstration of structural integrity of the cask container vessel from the view point of leakage and instable fracture. For the fracture evaluation, it has to be verified that brittle fracture does not occur at the lowest temperature -40degC.MHI has developed the MSF-57BG cask whose body is made of forged low alloy steel LF3-m. It is well known that low alloy steel has the brittle-to-ductile transition temperature range of fracture toughness and large scatter of toughness value in this region. For the cask's integrity evaluation, it is needed to obtain the fracture toughness dependent on temperature of this material by considering data scatter. The Master curve procedure [2] was proposed for estimation of fracture toughness of the pressure vessel on the basis of statistical procedure by using relatively small number of specimens.This paper examined the determination method of fracture toughness considering dynamic loading effect and data scatter in the brittle-to-ductile transition temperature by using the Master curve procedure.
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