United States Nuclear Regulatory Commission - Protecting People and the Environment

An Assessment of TRACE V5 RC1 Code Separator Model with the Westinghouse Model Boiler 2 Experiments (NUREG/IA-0224)

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Publication Information

Date Published: April 2010

Prepared by:
S. Hillberg

VTT—Technical Research Centre of Finland
Nuclear Power Plant Modeling
P.O.B. 1000
02044 VTT
Finland

Antony Calvo, NRC Project Manager

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

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Abstract

A TRAC/RELAP Advanced Computational Engine (TRACE) model of the Model Boiler 2 test facility has been built as part of the International Code Assessment and Maintenance Program (CAMP) validation case. Simulation cases with 100-percent and 50-percent power levels were run, and the results were compared to tests that were performed in the facility in the early 1980s. Because the main interest was in the functionality of the primary separator, the model includes no steam dryer assembly. The only heat structures built into the model were the primary-secondary heat transfer elements, since the model was run in a steady state and therefore the heat capacities of the structures had little effect on the results.

The Model Boiler 2 test facility failed to achieve the intended primary separator efficiencies in an oscillation-free system. Primary separator drain conditions had a major effect on the stability of the system and on the efficiency of the separation. A bigger drain area resulted in separation levels that were closer to the set value, but the system drifted easily into heavy oscillation. When the drain area was smaller, the separation levels were not achieved, but the system became more stable.

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