United States Nuclear Regulatory Commission - Protecting People and the Environment

ICAP [International Code Assessment and Applications Program] Assessment of RELAP5/MOD2, Cycle 36.05 Against LOFT [Loss of Fluid Test] Small Break Experiment L3-7 (NUREG/IA-0031)

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Publication Information

Date Published: April 1990

Prepared by:
Euy-Joon Lee, Bud-Dong Chung, Hho-Jung Kim

Nuclear Safety Center
Korea Advanced Energy Research Institute

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

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

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Abstract

The LOFT small break (1 in-dia) experiment L3-7 has been analyzed using the reactor thermal hydraulic analysis code RELAP5/MODZ, Cycle 36.05.

The base calculation (Case A) was completed and compared with the experimental data. Three types of sensitivity studies (Cases B, C, and D) were carried out to investigate the effects of (1) break discharge coefficient Cd, (2) pump two-phase difference multiplier and (3) High Pressure Injection System (HPIS) capacity on major thermal and hydraulic (T/H) parameters. A nodalization study (Case E) was conducted to assess the phenomena with a simplified nodalization.

The results indicate that Cd of 0.9 and 0.1 fit to the single discharge flow rate of Test L3-7 best among the tried cases. The pump two-phase multiplier has little effects on the T/H parameters because of the low discharge flow rate and the early pump coast down in this smaller size SBLOCA. But HPIS capacity has a very strong influence on parameters such as pressure, flow and temperature. It is also shown that a simplified nodalization could accomodate the dominant T/H phenomena with the same degree of code accuracy and efficiency.

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