United States Nuclear Regulatory Commission - Protecting People and the Environment

Qualification of the Three-Dimensional Thermal Hydraulic Model of TRACE using Plant Data (NUREG/IA-0242)

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Publication Information

Manuscript Completed: December 2007
Date Published: April 2011

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

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

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In this report the investigations performed to validate the 3D thermal hydraulic model of TRACE using data gained in the nuclear power plant Kozloduy Unit 6 regarding the coolant mixing within the reactor pressure vessel will be presented. These data were distributed to the scientific community in the frame of the VVER-1000 Coolant Transient Benchmark Phase 2. The measured data was recorded during the non-symmetrical core heat-up test caused by the closure of the isolation valve of the steam line of the loop-1. Since plant data for code validation is rather scarce, this coolant mixing data is very much appropriate for the qualification of the 3D thermal hydraulic models of the TRACE code.

A detailed multidimensional model for the RPV of the VVER-1000 was elaborated using the 3D VESSEL component of TRACE. The complete model consisted of more than 1000 3D thermal hydraulic cells. Using this model a post test analysis of the heat-up test was performed with the TRACE version V4160 in a Linux cluster.

The obtained results for the initial and final state are in very good agreement with the plant data. TRACE needed not more than six minutes for the simulation of the whole test duration of 1800 sec. It was demonstrated that the chosen 3D-nodalization of the RPV is adequate for the description of the coolant mixing phenomena in a VVER-1000 reactor.

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