United States Nuclear Regulatory Commission - Protecting People and the Environment

Loss of External Load Analysis with RELAP5/MOD3.3 Patch 03 Code (NUREG/IA-0249)

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Publication Information

Manuscript Completed: September 2010
Date Published: December 2010

Prepared by:
Andrej Prošek, Borut Mavko

Jožef Stefan Institute
Jamova cesta 39
SI-1000 Ljubljana, Slovenia

A. Calvo, NRC Project Manager

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
Under the International Code Assessment and Maintenance Program (CAMP)

Prepared for:
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

By removing resistance temperature detectors (RTD) bypass manifold system with fast-response thermowell-mounted RTDs the reactor coolant system temperature measurement time may change, what influences the time delays for overtemperature ΔT (OTΔT) and overpower ΔT (OPΔT) trips. The total time delays should not exceed the value assumed in the accident analyses.

In this paper we are presenting Krško nuclear power plant specific analysis of loss of external load varying the total delay time for OTΔT trip. For simulations the latest RELAP5/MOD3.3 Patch 03 thermal hydraulic computer code was used. The verified standard RELAP5/MOD3.3 input model from 2008 (cycle 23) was delivered by Krško nuclear power plant. Base case calculation was compared to safety analysis report calculation to qualify the RELAP5 calculated results before the sensitivity analyses were performed.

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