United States Nuclear Regulatory Commission - Protecting People and the Environment

RELAP5/MOD3.2.2 Gamma Assessment for Pressurized Thermal Shock Applications (NUREG/CR-6857)

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Publication Information

Manuscript Completed: October 2004
Date Published:

Prepared by:
C. D. Fletcher†, D. A. Prelewicz, W. C. Arcieri

Contributors:
M. A. Bolander, D. L. Mlynarczyk, K. C. Wagner§, R. Anderson, J. Cajigas

Michael B. Rubin, NRC Project Manager

ISL, Inc.
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Applied Analysis Corp.
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Idaho Falls, ID 83415

§Innovative Technology Solutions, Inc..
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Kent, WA 98032

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

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Abstract

The RELAP5/MOD 3.2.2 Gamma computer code has been used to simulate overcooling and/or pressurization events that have the potential to result in pressurized thermal shock (PTS) in the reactor vessels of pressurized water reactors. An assessment of this code version is reported here to establish the suitability of the computer code for analyzing transients that may be significant PTS risk contributors. Code assessment principally consists of performing calculations for a specific test in an experimental facility and comparing the calculated results to the measured data from the experimental facility.

Prior assessment of the RELAP5 code series has been performed for a wide variety of transients over the 20-year development history of the code. Many of these assessments focused on loss-of-coolant accidents (LOCAs) where the purpose of the analysis is to demonstrate core integrity during postulated licensing basis transients. For LOCAs, conditions in the core region are of principal interest. In contrast, for PTS related transients the focus is on the temperature and pressure conditions in the reactor vessel downcomer. Hence the assessment reported here focuses on comparing RELAP5 results with experimental data for conditions in the downcomer. Note that LOCA can be an important risk contributor to PTS and so assessments using LOCA tests remain relevant.

This report presents assessments that demonstrate the suitability of the code for analyzing PTS transients.

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