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SPECIAL SECTION: SELECTED PAPERS FROM THE INTERNATIONAL YOUTH NUCLEAR CONGRESS 2018 - 26TH WIN GLOBAL ANNUAL CONFERENCE

Validation of Selected Cesar Friction Models of the ASTECV21 Code Based on Moby Dick Experiments

[+] Author and Article Information
I. Gómez-García-Toraño

Institut de Radioprotection et de
Sûreté Nucléaire (IRSN),
Cadarache, bât 702,
Saint-Paul-lez-Durance 13115, France
e-mail: ignacio.gomezgarciatorano@irsn.fr

L. Laborde

Institut de Radioprotection et de
Sûreté Nucléaire (IRSN),
Cadarache, bât 702,
Saint-Paul-lez-Durance 13115, France
e-mail: laurent.laborde@irsn.fr

Manuscript received August 3, 2018; final manuscript received November 20, 2018; published online March 15, 2019. Assoc. Editor: Kevin Fernández-Cosials.

ASME J of Nuclear Rad Sci 5(2), 020908 (Mar 15, 2019) (9 pages) Paper No: NERS-18-1070; 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 Accident Source Term Evaluation Code (ASTEC) V2.1 integral code are validated against data from the Moby Dick test facility. Simulations are launched using two different numerical schemes: on the one hand, the classical five equation (drift flux) approach, with one momentum conservation equation for an average fluid plus one algebraic equation on the drift between the gas and the liquid; on the other hand, the recently implemented six equation approach, where two differential equations are used to obtain the phase velocities. The main findings are listed hereafter: The use of five 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 mass fractions 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 mass fractions. However, the qualitative prediction for high gas mass fractions still shows some deviations due to the decrease of the regular friction term at the end of the test section.

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References

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Figures

Grahic Jump Location
Fig. 1

Moby Dick test section considered for code validation

Grahic Jump Location
Fig. 2

Left: comparison of computational (solid lines) and experimental (dots) pressure profile at steady-state for selected single phase subsonic Moby Dick tests; right: contribution of each term of the momentum equation to the pressure gradient along the test section for the test 3154. Results obtained using CESAR 5 equations.

Grahic Jump Location
Fig. 3

Left: comparison of computational (solid lines) and experimental (dots) pressure profiles at steady-state for selected two phase subsonic Moby Dick tests involving low (first row), moderate (second row) and high (third row) gas titles; right: contribution of selected friction terms to the pressure gradient along the test section for the tests 3103, 3116, 3133 (low, moderate, and high gas titles). Results obtained using CESAR 5 equations.

Grahic Jump Location
Fig. 4

Left: comparison of predicted (solid and dashed lines) and experimental (dots) pressure profile at steady-state for selected single phase Moby Dick tests; solid and dashed lines correspond to CESAR five- and six-equation modeling, respectively; right: contribution of selected friction terms to the pressure gradient along the test section for the test 3154 using CESAR 6 equations

Grahic Jump Location
Fig. 5

Left: comparison of computational (solid and dashed lines) and experimental (dots) pressure profiles at steady-state for selected two phase subsonic Moby Dick tests involving low (first row), moderate (second row), and high (third row) gas titles; solid and dashed lines correspond to CESAR five- and six-equation modeling, respectively; right: contribution of selected friction terms to the pressure gradient along the test section for the tests 3103, 3116, 3133 (low, moderate, and high gas titles) using CESAR 6 equations

Grahic Jump Location
Fig. 6

Predicted (solid and dashed lines) and experimental (dots, if there were experimental data) pressure, void fraction, liquid and gas velocity profiles at steady-state for selected two phase subsonic Moby Dick tests involving high gas titles. Solid and dashed lines correspond to CESAR 5 and 6 equations, respectively.

Grahic Jump Location
Fig. 7

Relative deviation between predicted and experimental axial pressure drop when using CESAR the five (left) and six (right) equation model, where each point represents a given simulation/experiment. Points are colored according to the relative error in the pressure drop prediction.

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