Assessment of Two-Phase Critical Flow Models Performance in RELAP5 and TRACE Against Marviken Critical Flow Tests (NUREG/IA-0401)

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Publication Information

Manuscript Completed: June 2011
Date Published: February 2012

Prepared by:
Lukasz Sokolowski
Tomasz Kozlowski

A. Calvo, NRC Project Manager

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

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

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The project aims to (1) conduct the validation of thermal-hydraulics codes RELAP5 Mod 3.3 Patch 03 and TRACE v5.0 Patch 2 on the critical flow experiment giving comprehensive knowledge about the codes' behavior; (2) provide information about sensitivity impact of user-defined variables of critical two-phase models implemented into the codes; (3) and to obtain statistical data for variety of length-to-diameter L/D ratios of pipe. The experimental set-up consisted of vessel, discharge pipe and the group of test nozzles. The vessel was 24.5 m high, with internal average diameter of 5.2 m. The discharge pipe was 6.308 m long with internal diameter of 0.72 m. A total number of nine nozzles was used in the experiment and is characterized by L/D ratios of 0.3, 1.0, 1.5, 1.7, 3.0, 3.1, 3.6 and 3.7. The main conclusions of the studies are that for Marviken Critical Flow Test (CFT) (i) RELAP5 Henry-Fauske model gives more accurate results than RELAP5 Ransom-Trapp (R-T) model; (ii) TRACE R-T gives better results than RELAP5 R-T; and (iii) the dependence between length-to-diameter L/D ratio of the nozzle and the calculation’s accuracy has not been observed.

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