United States Nuclear Regulatory Commission - Protecting People and the Environment

Assessment of RELAP5/MOD2 Cycle 36.04 with LOFT Large Break LOCE L2–3 (NUREG/IA-0070)

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Publication Information

Date Published: April 1992

Prepared by:
Y. S. Bang, H. J. Kim, Korea Institute of Nuclear Safety
S. H. Kim, Korea Atomic Energy Research Institute

Korea Institute of Nuclear Safety
P.O. Box 16, Daeduk-Danji
Daejoni 300–31
Republic of Korea

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
under the International Thermal-Hydraulic Code Assessment
and Application Program (ICAP)

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

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Abstract

The LOFT LOCE L2-3 was simulated using the RELAP5/MOD2 Cycle 36.04 code to assess its capability to predict the thermal-hydraulic phenomena in LBLOCA of the PWR. The reactor vessel was simulated with two core channels and split downcomer modelling for a base case calculation using the frozen code. From the results of the base case calculation, deficiencies of the critical flow model and the CHF correlation at high flow rate were identified, and the severeness, of the rewetting criteria were also found. Additional calculation using an updated version of RELAP5/MOD2 Cycle 36.04 including modifications of the rewet criteria shows a substantial improvement in the core thermal response.

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