Severe Accident Assessments for PLNGS PSA Support by MAAP5-CANDU Simulations

Abstract

A series of severe accident progression and consequence assessments on the CANDU® 6 reactor were performed for the Point Lepreau Nuclear Power Generation Station in support of the Level 2 probabilistic safety assessment. In the assessments, a modular accident analysis program, the MAAP5-CANDU computer code, was used. This work is in compliance with Canadian Nuclear Safety Commission regulatory documents REGDOC-2.4.1 and REGDOC-2.4.2, using the best estimate approach in deterministic safety analysis for severe accident assessments. The assessments include severe accident cases involving station black-out, loss-of-coolant accidents (LOCAs), in-core LOCAs, containment by-pass, seismically induced LOCAs, and accident events in the shutdown state. The MAAP models integrate the plant’s finalized design with containment emergency filtered venting and reactor vault make-up systems (which were installed during Point Lepreau refurbishment prior to Fukushima as a result of the Level 2 probabilistic safety assessment conducted in 2008), together with the spent fuel bay modelling. The assessments updated the previous work conducted for the Point Lepreau refurbishment project in 2008, and form the basis for using emergency mitigating equipment, as well as supporting Level 2 probabilistic safety assessments and severe accident management.