Break probability evaluation for a weld in piping of the water-cooled ceramic breeder blanket for CFETR

Abstract

The Water-cooled ceramic breeder (WCCB) blanket is one of the three major blanket design concepts for CFETR. Weld failures will result in the blanket failure and reduce blanket reliability. Especially, weld failures in piping of the blanket may cause loss of coolant accidents (LOCAs) which are typical initiating events in the probabilistic safety analysis (PSA) for CFETR. Determining the failure probabilities of welds at coolant piping in the blanket is necessary and helpful to evaluate the occurrence frequencies of the LOCAs, accelerating the construction of PSA reliability database for CFETR. The present paper provides a probabilistic model to estimate the probability of failure at a weld in coolant piping of WCCB blanket. A girth butt weld in piping of the first wall (FW) was chosen as the numerical example to demonstrate the model. The probabilities of the weld breakage over the design lifetime of CFETR were estimated. Sensitivity analyses for input parameters of the probabilistic model, such as operational temperature and pressure, were carried out as well, with results indicating that the effects of uncertainties associated with initial crack size and crack growth factor on break probabilities estimated are significant.