Validation of selected CESAR friction models of the ASTECV21 code based on Moby Dick experiments

[+] Author and Article Information
Ignacio Gómez

Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Cadarache, bât 702, 13115 Saint-Paul-lez-Durance, France

Laurent Laborde

Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Cadarache, bât 702, 13115 Saint-Paul-lez-Durance, France

1Corresponding author.

ASME doi:10.1115/1.4042119 History: Received August 03, 2018; Revised November 20, 2018


In the event of a loss of integrity of the Main Coolant Line, a large mass and energy release from the primary circuit to the containment is to be expected. The temporal evolution of such depressurization is mainly governed by the critical flow, whose correct prediction requires, in first place, a correct description of the different friction terms. Within this work, selected friction models of the CESAR module of the ASTEC V2.1integral code are validated against data from the Moby Dick test facility. Simulations are launched using two different numerical schemes: first, with the 5 equation approach, with one momentum conservation equation for an average fluid plus one algebraic equation on the drift between the gas and the liquid; then, with the recently implemented 6 equation approach, where two differential equations are used to obtain the phase velocities. The main findings are listed hereafter: • The use of 5 equations provides an adequate description of the pressure loss as long as the mass fluxes remain below 1.24 (kg/cm2/s) and the gas titles below 5.93*10^(-4). Beyond those conditions, the hypotheses of the drift flux model are exceeded and the use of an additional momentum equation is required. • The use of an additional momentum equation leads to a better agreement with the experimental data for a wider range of mass fluxes and gas titles. However, the qualitative prediction for high gas titles still shows some deviations due to the decrease of the regular friction term.

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