Containment Depressurization Capabilities of Filtered Venting System in 1000 MWe PWR with Large Dry Containment

Abstract

After the Fukushima Daiichi nuclear power plant accident, the Korean government and nuclear industries performed comprehensive safety inspections on all domestic nuclear power plants against beyond design bases events. As a result, a total of 50 recommendations were defined as safety improvement action items. One of them is installation of a containment filtered venting system (CFVS) or portable backup containment spray system. In this paper, the applicability of CFVS is examined for OPR1000, a 1000 MWe PWR with large dry containment in Korea. Thermohydraulic analysis results show that a filtered discharge flow rate of 15 [kg/s] at 0.9 [MPa] is sufficient to depressurize the containment against representative containment overpressurization scenarios. Radiological release to the environment is reduced to10-3considering the decontamination factor. Also, this cyclic venting strategy reduces noble gas release by 50% for 7 days. The probability of maintaining the containment integrity in level 2 probabilistic safety assessment (PSA) initiating events is improved twofold, from 43% to 87%. So, the CFVS can further improve the containment integrity in severe accident conditions.

Application of ASTEC, MELCOR, and MAAP Computer Codes for Thermal Hydraulic Analysis of a PWR Containment Equipped with the PCFV and PAR Systems

“…The passive containment filtered venting (PCFV) system and passive autocatalytic recombiners (PAR) are specially designed systems and equipment which operate in the most severe conditions without the need of an operator action. The reports and papers published in the open literature, some of them listed in [1][2][3][4], support the interest of nuclear facilities for such systems to restrict radioactive releases out of the NPPs. Influence of safety systems on containment behaviour is examined by calculating a station blackout event without any recovery actions with three integral severe accident codes: ASTEC, MELCOR, and MAAP.…”

A Conceptual Approach to Eliminate Bypass Release of Fission Products by In-Containment Relief Valve under SGTR Accident

“…Finally, the containment pressure reached 0.53 MPa and 0.8 MPa in the base-cavity flooding case and the ICRV-CNMT-cavity flooding, respectively. Although it is not low pressure, ultimate containment failure pressure of OPR1000 with 5% probability at 95% confidence level is 1.01 MPa [26]. Therefore, the cavity flooding method is potentially successful as a depressurization strategy because it reduced the containment pressure from 1.2 MPa to 0.8 MPa in the ICRV-CNMT case.…”