United States Nuclear Regulatory Commission - Protecting People and the Environment

Investigations of the VVER-1000 Coolant Transient Benchmark I with the Coupled Code System RELAP5/PARCS (NUREG/IA-0217)

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Publication Information

Date Published: December 2009

Prepared by:
V. Sánchez-Espinoza
Forschungszentrum Karlsruhe GmbH
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen

A. Calvo, NRC Project Manager

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

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This report presents the investigations performed to validate the coupled code RELAP5/PARCS using data of a pump restart-up test carried out at the Kozloduy nuclear power plant (KNPP). An integral plant model—including the relevant primary and secondary systems as well as a detailed model of the reactor pressure vessel and of the core—was developed for RELAP5 and PARCS to simulate the pump restart-up test. From the comparison of the thermal-hydraulic data obtained during the tests with the code's predictions, it can be stated that the overall trends of most plant parameters are in a reasonable agreement with the experimental data. The investigations have shown some limitations of 1D thermal-hydraulic coarse models of the downcomer, lower, and upper plenum. Hence, multidimensional thermal-hydraulic models are needed for a more realistic description of the coolant mixing phenomena within the reactor pressure vessel.

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