Analyses of radio-nuclides release and transport in VEGA-1 and -3 tests with VICTORIA2.0 code

Hidaka, Akihide*   ; Kudo, Tamotsu ; Kida, Mitsuko; Fuketa, Toyoshi

In the VEGA program to investigate radionuclides release from irradiated fuel during severe accidents, the analyses are being performed with VICTORIA2.0 code for comprehensive understanding of radionuclides release and transport phenomena. The VEGA-1 and -3 tests were analyzed in the present study. The correlation for Cs diffusion coefficient in fuel grain obtained from VEGA-1 was applied to the release analysis of VEGA-3. The calculated release of Cs agreed well with the measurement. The correlation was applied to subsequent Cs transport and deposition analyses. The calculation underpredicted the total mass of Cs deposited onto the test apparatuses because nucleation of aerosol and its growth were underestimated due to the consideration of aerosol nucleation originated only from released FP in VICTORIA2.0. A sensitivity analysis with aerosol seeds for heterogeneous nucleation showed a reasonable agreement with the measured Cs distribution. It turned out that additional aerosol seeds besides the released FP be considered when the VICTORIA2.0 code is applied to the VEGA test analyses.