Validation study of the sodium-water reaction thermohydraulic analysis code, SWAC13E.REG2; Large leak sodium-water reaction analysis (Report No.16)

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To enhance the degree of analytical accuracy of a large leak sodium-water reaction in an LMFBR steam generator, the Long-Term Sodium-Water Reaction Thermohydraulic Analysis Code, SWAC13E, was modified and validated using experimental results. In the present study, besides the refinement of the two-phase flow model utilized in the code, a relative velocity and a heat transfer equation corresponding to each flow regime were newly provided. Following the modification, the calculational results were compared with the data of SWAT-3 Runs4, 5, 6, and 7. As the results of the modification, over-conservatism of fluid temperatures existing in the conventional model was reduced to a proper degree and the calculational results of temperatures and pressures agreed well with the experimental data. The prediction of a sodium mass expelled to the reaction products tank was improved, but it has still a certain degree of conservatism. This validation study revealed that SWAC13E.REG2 could replace the quasi-static pressure calculation module of SWACS, which had been used for the large leak analysis since the Construction Permission of the Prototype FBR, Monju.