Probabilistic fracture mechanics conditional probability

The event frequencies and conditional failure probabilities used to evaluate vessel integrity in the USA are distributions. Probabilistic fracture mechanics computations generate distributions of conditional probability of initial flaw extension (CPI) and conditional probability of vessel failure (CPF) for each transient event and a number of statistically sampled trial pressure vessels. The CPF distributions and the frequency distributions for each transient event are combined to generate a TWCF distribution for the population of trial vessels and events. The individual TWCF values in the distribution are ... 

The sequences of events that may lead to vessel failure and their frequencies are determined from probabilistic risk assessment (PRA) analyses. The pressure, temperature and heat transfer coefficient time histories at the vessel inner surface are determined from thermal hydraulic analyses for the events identified by the PRA analyses. These time histories are used together with probabilistic fracture mechanics (PFM) analysis to calculate the conditional probability of RPV failure. Discussion of the methodology used to perform the PRA analyses and define the transient events and associated frequencies, and the thermal hydraulic analyses used to define the event pressure and temperature time histories are outside the scope of this chapter. Consequently, the remainder of this chapter focuses on the PFM evaluation assumptions and procedures. 

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