Assessment of RELAP5/MOD3.2 for Thermohydraulic Processes in Heated Rod Bundles with Tight Lattice at CKTI Test Facility (NUREG/IA-0168)

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Publication Information

Date Published: October 1999

Prepared by:
A. S. Devkin

Nuclear Safety Institute
Russian Research Center
"Kurchatov Institute"
123182, Moscow

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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The assessment of RELAP5/MOD3.2 for two-phase hydrodynamics and heat transfer processes in the rod bundle model with tight lattice are presented. This experiments have been carried out at the bundle with non-standard geometrical characteristics - close packed assembly and small hydraulic diameters. The investigations have been carried out at the following range of parameters: pressures P = 0.23-2.0 MPa, inlet water flowrate from zero up to G=17-18.3 kg/c, heat fluxes q–up to 0.96 kW/m2 and void fractions α = 0.03 –0.89.

RELAP5/MOD3.2 assessment for processes at steady state conditions at small or zero flowrates at the inlet of the tube bundle showed that for such processes code gives rather good results. The comparison of computed and experimental results for process of boil-off and reflooding shows that there is a good coordination between computed and experimental values between temperatures of pipe bundle walls for upper part of the bundle. For lower part of the bundle there are some discrepancies between computed and experimental values of temperature, the later being some lower than experimental ones. The calculated values of shroud temperature were rather less than experimental ones.

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