Behavior of Heat Embrittlement in Welded Pipe of Nuclear Plant and Probabilistic Estimation of Safety and Reliability
Nagatoshi OKABE, Maho HOSOGI, Akira NISHIHARA and Tomoya ICHIKAWA
Abstract:Embrittlement behavior of the duplex stainless steel in the intermediate temperature range(275 to 500Ž) is one of the very serious problems for applying reliability assessment to practical pipes in a nuclear power plant. In this work, it is shown by formularization of embrittlement behavior with aging time that the increase in hardness due to embrittlement is governed by ƒ¿ contents of the duplex stainless steel. The formula as function of aging time and temperature, which can predict the embrittlement behaviors in the duplex stainless steel of arbitrary chemical compositions, is proposed by using the Schefflerfs statechart diagram. For the purpose of estimating the structural reliability of a nuclear power plant, the formula can be used to predict the change of fracture toughness KIC with service term in the field probabilistically. Key Words:Duplex stainless steel, ƒ¿ content, Emblittlement, Schefflerfs statechart diagram