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Yoshikawa, Shinji; Sato, Ikken
no journal, ,
Steam and hydrogen generation history and gas leakage area are inversely evaluated by a thermal hydraulic analysis code GOTHIC. The analyzed period in the accident progression is from the arrival of reactor liquid level at the top of active fuel (TAF) until start of depressurization of reactor pressure vessel(RPV) by activation of automatic depressurization system(ADS). Based on the measured behaviors of the RPV and PCV pressures from 6:30 of March 13th until the ADS activation, some leakage from RPV to PCV is supposed during this period. The leakage path and area are inversely derived on plural possible accident scenarios. The leakage area are estimated to be no greater than 1 cm
. This result suggests that the gas flow at the time of the main slumping would have been through S/C, where vapor condensation was effective, thus certain contribution of non-condensable gases like hydrogen seems necessary to explain the observed D/W pressure increase.
Yoshikawa, Shinji; Sato, Ikken
no journal, ,
Steam and hydrogen generation history and leakage scale from RPV of Fukushima Daiichi Nuclear Power Plant unit 3 to reproduce the measured pressure history of RPV and PCV were inversely analyzed using a thermal hydraulic code GOTHIC. The leakage area from RPV to reproduce the measured decrease behavior of RPV pressure is evaluated to be around 1 cm, regardless of the assumed leakage paths. Since some of SRVs are supposed to have been open at the time of the major slumping (~12:00 of March 13), provided that the leakage area was kept ~1cm, its effect on PCV pressure would have been negligible. In this case, the gas flow at the time of the main slumping would have been through S/C, where vapor condensation was effective, thus certain contribution of non-condensable gases like hydrogen seems necessary to explain the observed D/W and S/C pressure increase.