Analysis of the RELAP5/MOD3.2.2beta Critical Flow Models and Assessment Against Critical Flow Data From the Marviken Tests (NUREG/IA-0186)

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Publication Information

Date Published: July 2000

Prepared by:
C. Queral, J. Mulas, C. G. de la RĂșa

Energy Systems Department
School of Mining Engineering
Polytechnic University of Madrid

Prepared as part of:
The Agreement on Research Participation and Technical Exchange
under the International Code Application and Maintenance Program (CAMP)

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

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In this report the critical flow models of RELAP5/MOD3.2.2beta have been analized. Firstly, an analysis of the implementation of the RELAP5/MOD3.2.2beta models have been performed in which it has been proved that the transition from the critical to the non-critical flow model is not well done for the Ransom-Trapp model. Secondly, a sensitivity analysis of both models (Ransom-Trapp and Henry-Fauske) in subcooled, two-phase and vapor conditions has been taken with respect to temperature, pressure, void-fraction, discharge coefficients, energy loss coefficient and disequilibrium parameter. Finally, seven Marviken tests have been simulated and compared with the experimental data in order to validate both models. As a part of this assessment, an adjustment of the discharge coefficients for the Ransom-Trapp model with different nodalizations has been done and also it has been checked which are the best values of the disequilibrium parameter for the Henry-Fauske model in subcooled and two-phase conditions. Conclusions indicate that the behaviour of the Henry-Fauske model is better than that of the Ransom-Trapp. In this sense, the new model is an improvement with respect to the Ransom-Trapp.

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