Abstract
Because of frequent failures of the Atucha PWR moderator circuit branch piping, which is made of stainless steel type AISI 347 (DIN 1.4550), studies have been made, involving the application of several fracture mechanics criteria, in order to determine the conditions of leak-before-break (LBB) and the critical crack length of the piping. These studies lead to the conclusion that, for straight pipe of outside diameter 219 mm and 16 mm wall thickness, with a circumferential flaw and with the principal stress being in bending, the LBB criteria are satisfied, the critical crack length being of the order of 400 mm. A better mechanical finishing and heat treatment was suggested in order to improve the resistance to crack initiation.
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