Life forecasting of welded elements of fast breeder reactor according to evaluation of creep damage

This study aims at precision upgrading of construction soundness evaluation at abnormal and accidental times, foundation establishment on life forecasting of welded elements at middle and later periods of the FBR life, and contribution to upgrading of its safety, by quantifying time dependent type creep damage accumulated at welded portions in reactor vessel or primary pipings under steady and unsteady operation conditions of the FBR. Therefore, on an object of welded joints of austenitic stainless steel (304 and 306FR) and ferritic heat resistant steel (2.25Cr-1Mo and improved 9Cr-1Mo) constituting of the primary system in FBR, the following three theme were carried out: 1) development on a creep strain equation using macroscopic continuous body dynamics, 2) development on detection and quantification technologies of microscopic creep damage, and 3) development on simulation of the creep damage. In 1998 fiscal year, together with detail investigation on creep deformation behavior of the mother materials for the 340HP steel thick plate welded joint, elucidation on creep fracture of the 2.25Cr-1Mo steel welded joint was carried out. And, relationship between creep damage process and supersonic property of the 304 steel was investigated at a viewpoint of metallic texture and transition density. In addition, in order to conduct creep damage simulation more precisely, local change on creep strain of the 316FR steel multi-layer welded joint was tried to observe by the moire interference method using a CCD camera developed by the National Research Institute for Metals. (G.K.)