United States Nuclear Regulatory Commission - Protecting People and the Environment

CFD Analysis of 1/7th Scale Steam Generator Inlet Plenum Mixing During a PWR Severe Accident (NUREG-1781)

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Publication Information

Manuscript Completed: September 2003
Date Published:
October 2003

Prepared by:
C.F. Boyd, K. Hardesty

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

Computational fluid dynamics (CFD) is used to predict steam generator inlet plenum mixing during a severe accident scenario in a pressurized water reactor. Comparisons are made to 1/7th scale data. Qualitatively, the code predicts the experimental flow patterns and mixing phenomena. Quantitatively, comparisons are made with key temperatures, mass flows, and mixing parameters. The best estimate prediction is generally within 5% of the reported values. Key temperature predictions are within a few degrees K of the test data. Boundary conditions applied to the model include the hot leg inlet mass flow and temperature as well as the tube secondary side temperature and heat transfer. The mass averaged temperature of the flow entering the tubes is predicted to within 1 degree of the experimental data. The mass flow through the tube bundle is predicted to within 0.5% of the data. The number of hot tubes is overpredicted by 7 tubes out of the 216 total. The mixing fraction and the recirculation ratio, both important mixing parameters, are predicted to within 5% of the data. These predictions provide confidence in the code and modeling approach. The secondary side heat transfer coefficient is determined to be the dominant governing parameter.

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