Probabilistic Fracture Mechanics Code--PRAISE-CANDU 2.1

Abstract

PRAISE-CANDU, a Monte Carlo based Probabilistic Fracture Mechanics (PFM) software has been developed for use in fitness-for-service assessment, risk-informed in-service inspection and large-break loss-of-coolant accident reclassification. The software has the capability to model crack initiation, crack growth and crack stability for degradation mechanisms including fatigue, stress corrosion cracking (SCC), and flow accelerated corrosion (FAC) as well as material aging (i.e. time dependent material properties). The combination of all four mechanisms, which is important for CANDU piping systems, is a unique feature of PRAISE-CANDU.

Since the development of the initial version in 2013, significant technical advancements in fracture mechanics have been achieved, especially in crack opening area, crack transitioning and stress intensity factor solutions for circumferential cracks. In addition, there is growing importance of considering axial cracks in the piping bend/elbow for leak-before-break (LBB) application. International benchmark projects have allowed cross-verification of the software and identified areas for improvement. Based on these latest developments and the knowledge gained in the industry, PRAISE-CANDU has been updated to Version 2.1 and compliant with CSA Standard N286.7-16. This paper summarizes the technical advancements and new capabilities of PRAISE-CANDU 2.1. The results for several benchmarking test cases with other PFM software and plant operating experience for fatigue, PWSCC and FAC degradation mechanism are also presented.