APPLICABILITY AND EFFECTS ON SAFETY IMPROVEMENT OF CONTAINMENT FILTERED VENT SYSTEM IN OPR1000

摘要

After the Fukushima Dai-ichi nuclear power plant accident, the Korean government and nuclear industries performed comprehensive special safety inspections on all domestic nuclear power plants against beyond design bases external events. As a result, a total of 50 recommendations were defined as safety improvement action items. One of the major action items is installation of a containment filtered vent system or temporary backup containment spray system. In this paper, the applicability and effects on safety improvement of containment filtered vent system (CFVS) in OPR1000, 1000MWth PWR in Korea, are examined. Thermo-hydraulic analysis results show that a filtered discharge flow rate of 6 [kg/s] is sufficient to depressurize the containment against major severe accident scenarios. When containment pressure reaches CFVS operating set-point at approximately 11 hours after the initiating events, CFVS effectively depressurizes the containment and maintains its integrity. In addition, the probability of maintaining the containment integrity in level 2 Probabilistic Safety Assessment (PSA) initiating events is improved two-fold, from 43% to 86%. The CFVS can thus further improve the safety of containment integrity in OPR1000 with respect to the severe accident mitigation strategy and PSA. As a further study item, adverse effects, such as containment negative pressure and local hydrogen concentration buildup, should be examined to guarantee the overall safety improvement effects of the CFVS.