United States Nuclear Regulatory Commission - Protecting People and the Environment

RELAP5 and TRACE Simulation of Hot Leg Break LOCA Experiment on LSTF (NUREG/IA-0494)

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Publication Information

Manuscript Completed: November 2017
Date Published: December 2018

Prepared by:
Andrej Prošek

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

Kirk 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)

Published by:
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Availability Notice


Confidence in the computational tools and establishment of their validity for a given application depends on the assessment. The purpose of this study is therefore to independently assess the TRACE computer code for hot leg break test. A pressurized water reactor (PWR) hot leg break loss-of-coolant accident experiment SB-HL-02 was performed on the Large Scale Test Facility (LSTF) in the Rig of Safety Assessment-IV (ROSA-IV) program with a break size equivalent to 10% cold leg cross sectional area. For calculations the RELAP5/MOD3.3 Patch 5 and TRACE V5.0 Patch 4 computer codes were used. The RELAP5/MOD2 input model was obtained within the framework of International Atomic Energy Agency (IAEA) Coordinated Research Project (CRP) on Evaluation of Uncertainties in Best Estimate Accident Analysis (2006-2010). The obtained input model was first adapted to RELAP5/MOD3.3 and then converted to TRACE using Symbolic Nuclear Analysis Package (SNAP), requiring also manual corrections. The LSTF simulates a Westinghouse-type four-loop 3423 MW (thermal) PWR by a full-height and 1/48 volumetrically-scaled two-loop system. The results suggest that TRACE calculation is comparable to RELAP5 calculations and that results obtained by both codes agree well with the experimental data. Finally, it was also demonstrated that advanced SNAP graphical user interface has the capabilities to graphically present complex phenomena like collapsed liquid level distribution in the loop, helping to understand natural circulation flow in different regimes.

Page Last Reviewed/Updated Thursday, December 20, 2018