Abstract
Probabilistic and deterministic integrity analyses of piping are important issues with regard to the integrity and reliability of nuclear power plant (NPP) components. Since there is an ongoing controversial discussion concerning the positive and negative influence of weld residual stress (WRS) on the failure probabilities of piping with dissimilar metal welds (DMWs), we herewith present the analysis of a representative straight pipe with DMW in a boiling water reactor (BWR). In this case, we consider the WRS profile, internal pressure (IP), bending stress (BS), stress corrosion cracking (SCC) and relative depth (a/t) of circumferential cracks at the inner pipe wall for the calculation of crack growth and break probabilities by using the PROST software. Probabilistic analyses show that the dependence of various break probabilities of components is not only on WRS distribution profiles but also on the crack geometry. The analyses reveal that the break probability may increase nearly 100 times due to an increase of the WRS by a factor of 1.5. The sensitivity of the stress intensity factors on the WRS profile, IP, BS, SCC and on the relative crack depth (a/t) is compared.
Highlights
Nuclear energy is the second largest low-carbon energy source worldwide and may play a significant role in decarbonizing the world’s energy system [1]
The PROST software is able to deal with two kind of crack initiation, including the initial cracks formed during manufacturing and the cracks developed during the operation due to loading conditions
Both probabilistic and deterministic analyses of a straight pipe with DWMs in the primary loop of a boiling water reactor (BWR) is presented, wherein the damage mechanism of stress corrosion cracking (SCC) involved with weld residual stress (WRS), internal pressure and bending stress is considered
Summary
Nuclear energy is the second largest low-carbon energy source worldwide (after hydropower) and may play a significant role in decarbonizing the world’s energy system [1]. There exists a long-standing concern regarding the long-term operation (LTO) of nu clear power plants (NPPs), including the structural integrity and reli ability of components [2]. It is well-known that NPP components are sensitive to degradation mechanism, such as fatigue and stress corrosion cracking (SCC) [3]. The occurrence of SCC is determined by the following three conjoint factors: a corrosive environment, a susceptible material, and high tensile stress (including residual stress). The influence of WRS on SCC is not yet fully clarified; the knowledge of acting (primary and secondary) operating and residual stresses in a NPP component is very essential
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