An updated probabilistic fracture mechanics methodology for application topressurized thermal shock

The US Nuclear Regulatory Commission (NRC) is, in concert with the US nucle ar industry, currently revisiting its rule and analysis requirements for pr essurized thermal shock (PTS) scenarios. This paper provides an overview of an updated probabilistic risk analysis (PRA) methodology that is continuin g to evolve as part of that effort. The evolution process includes a carefu l assessment of recent advancements that have been made in the various part s of the computational methodologies. The process also involves interaction s between experts in relevant disciplines (thermal hydraulics, PRA, materia ls, fracture mechanics, and non-destructive and destructive examination). R epresentatives include staff members from the USNRC staff, research laborat ories, and the nuclear industry. The updated methodology is being integrate d into the FAVOR (Fracture Analysis of Vessels: Oak Ridge) computer code fo r application to re-examine the adequacy of the current regulations and to determine if the updates provide sufficient technical bases for revisions. This paper also discusses recent modifications to the probabilistic fractur e mechanics (PFM) methodology that is central to FAVOR. (C) 2001 Elsevier S cience Ltd. All rights reserved.