Abstract

Under the severeaccident condition, the containment is the last shielding for preventing the accidentalrelease of radioactive fission products to the atmosphere. To figure out the failure margin in accident conditions, it is necessary to research and analyze the effects of surface liquid film coverage on the containment safety. The Passive Containment Cooling System’s thermal-hydraulic model has been built with passive containment analysis code in Large Power Passive Reactor. Based on the reference conditions of Double Ended Guillotine (DEG) on a cold leg and Main Steam Line Break (MSLB), the sensitivity analysis of parameters related to surface liquid film coverage has been performed, the cases of the water distribution tube failure and the spray pipe pluggage added the failure of water distribution tube, and the scram under different power level have been carried out, respectively. Results: The analysis results show that: (1) the containment would fail in 24 hours after DEG accident start as a result of the liquid film coverage lower than 45%; (2)under the MSLB condition, the containment pressure is highest when scram power level is 30% of Fission Power (FP) under keeping the design liquid film coverage, and with the decrease of liquid film coverage, the containment is not failing as a result of overpressure, although the pressure is highest on the scram power level 0% FP.

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