Uncertainty and Sensitivity Analysis of Hot Leg LOCA in Two-Loop PWR Using RELAP5 Version 3.3lj (NUREG/IA-0547)

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Publication Information

Manuscript Completed: November 2023
Date Published: April 2024

Prepared by:
Andrej Prošek Jožef Stefan Institute
Jamova cesta
39 SI-1000, Ljubljana, Slovenia

K. Tien, NRC Project Manager

Division of Systems Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Prepared as part of
The Agreement on Research Participation and Technical Exchange
Under the Thermal-Hydraulic Code Applications and Maintenance Program (CAMP)

Published by
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

The reactor pressure vessel (RPV) is vulnerable to occurrence of pressurised thermal shock (PTS) in a pressurised water reactor (PWR). PTS can occur during several overcooling scenarios, including loss of coolant accidents. Thermal hydraulic calculations of overcooling scenarios provide an input to structural analysis. The purpose of this study is to perform the calculation of hot leg small break loss of coolant accident with uncertainty and sensitivity analysis. The reactor selected was two-loop PWR, for which verified and validated input deck was available. For analysis the RELAP5 developmental version 3.3lj from 2022 with built-in code uncertainty parameters has been used. For uncertainty and sensitivity analysis Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) Data Processing program Software for Uncertainty and Sensitivity Analyses (SUSA) Version 4.2.5 has been used. For uncertainty and sensitivity analysis 208 RELAP5 runs have been performed. The three figures of merit selected for uncertainty analysis were reactor pressure, liquid temperature and reactor vessel wall temperature below the cold leg connection.

The results are presented for reference calculation, sensitivity study varying one parameter at a time and uncertainty and sensitivity analysis.