Forecasting the parameters of crack resistance of dissimilar welded joints of Du800 MCP and MCP pipelines of WWER-1000 reactor to substantiate the applicability of the “leak before break” concept

The article presents the results of studies of the data on crack resistance characteristics of dissimilar welded joint metal of the main circulation pipeline insert and the branch pipe of main circulation pump. The obtained data are necessary for performing calculations to justify “Leak-before-break” concept application at lifetime extension of the main circulation pipelines of VVER-1000 reactor to 60 years (up to 520 thousand hours). The studies were performed on specimens from manufactured control welded joints of DN800 pipeline insert made of steel grade 10GN2MFA to the main circulation pump branch pipe made of steel grade 06Kh12N3DL. Studies of crack resistance were carried out to obtain J_r-curves of the weld metal, made by manual and automatic welding, and the transition weld zone in the initial state and after thermal aging in the operating temperature range from 100°C to 290°C state. According to the predicted values of T_k(τ), the values of the fracture toughness K_jc(τ), as well as the impact strength KCV at design temperature of 290°C for the end of the service life are estimated.

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