RELAP5 and TRACE Simulation of Bethsy 9.1b Test with Accuracy Quantification (NUREG/IA-0531)

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Publication Information

Manuscript Completed: November 2021
Date Published: April 2022

Prepared by:
Andrej Prošek, Boštjan Končar

Jožef Stefan Institute
Jamova cesta 39
SI-1000, Ljubljana, Slovenia

K. Tien, NRC Project Manager

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

Prepared as part of
The Agreement on Research Participation and Technical Exchange
Under the Thermal-Hydraulic Code Applications and Maintenance Program (CAMP)

Availability Notice


In this study the TRACE advanced thermal-hydraulic system code has been used to simulate the BETHSY 9.1b integral experimental test. The TRACE results are compared with the RELAP5 computer code predictions. In addition, the accuracy of both simulations has been evaluated. BETHSY is an integral test facility, which was designed to simulate most pressurized water reactors (PWR) accidents of interest, to study accident management procedures and to validate the computer codes. The BETHSY 9.1b experiment represents the Small Break Loss-of-Coolant Accident (SBLOCA) with loss of high pressure injection system. After the Fukushima-Daiichi nuclear accident, this type of accident is considered as a part of Design Extension Conditions (DEC). As no DEC safety features for high pressure injection are available in BETHSY 9.1b test, a delayed operator action for secondary system depressurization has been analysed in this study. For accuracy quantification the Fast Fourier Transform Based Method by signal mirroring (FFTBM-SM) and original FFTBM have been used. The comparison of the simulated results with the experimental data is presented. Finally, the results of code accuracy quantitative assessment are shown.

Page Last Reviewed/Updated Thursday, April 14, 2022