State of the Art for Thermal-Hydraulic Analysis of Pressurised Thermal Shock Scenarios

Abstract

Most of the nuclear power plants (NPPs) in the European Union (EU) are currently in the second half of their designed lifetime and numerous projects have been initiated to increase knowledge of their safety level, life span and capacity factor. Within the scope of long-term operation (LTO) progammes, pressurized thermal shock (PTS) has been identified as one of the limiting safety considerations, where the safety margin against fast fracture initi-ation of reactor pressure vessel (RPV) failure must be demonstrated. Accurate analysis of loads in RPV of pressurized water reactors (PWRs) requires knowledge of the local ther-mal-hydraulic (TH) parameters for different operational scenarios. These parameters are obtained through TH analysis of relevant cases. In the Advanced PTS Analysis for LTO (APAL) project funded by Euratom research and training programme, a literature review and collection of experience and current practices has been carried out to define the current state-of-the-art in the field of TH analysis for PTS scenarios. Experience from the APAL partners was collected through a questionnaire in order to assess the state-of-the-art based on national practices. The limitations of computer codes used for mixing analysis are dis-cussed. The results of previous projects focused on TH analysis and uncertainty quantifica-tion (UQ) relevant for PTS analysis have been collected and summarized. The available experimental TH data for PTS from validation of TH computer codes and development of UQ methods have been collected.