Rupture Frequency of CANDU^® Large-Diameter Primary Heat Transport Piping Estimated Using Probabilistic Fracture Mechanics Codes

This paper presents a pilot study of using probabilistic fracture mechanics codes (PRO-LOCA 2009 and WinPRAISE 2007) to estimate the rupture frequency of CANDU^® large diameter Primary Heat Transport (PHT) piping. The results of this study show that WinPRAISE 2007 and PRO-LOCA 2009 produce comparable trends for the predicted probability of leak and probability of large break leak. There is a number of sensitive leak detection methods available in CANDU plants. The materials and quality of fabrication and sensitive leak detection results in the total probability of a large break leak in the large diameter PHT piping welds being estimated to be on the order of 1E−8 breaks per plant per year. The results of the pilot study indicate that probabilistic fracture mechanics codes could be used to demonstrate that a shutdown action limit of 100 kg/h is sufficient to ensure the probability of rupture of large diameter PHT piping welds is extremely low.