Development and Application of an Operational Probabilistic Risk Assessment (PRA) at Ontario Power Generation

Abstract

Ontario Power Generation Inc. has embraced the use of Probabilistic Risk Assessment (PRA) in operational decision-making. Common examples include decisions related to continued operation while in an abnormal plant configuration based on incremental risk increase, and the use of risk monitors (i.e., Equipment Out-of-Service (EOOS)) for outage planning and managing risk during on-line maintenance. Unlike the baseline PRA where average risk is calculated, these operational decisions/tools are best made using a real-time, or instantaneous analysis reflecting actual plant configuration. The process of taking the baseline, time-averaged PRA, to an instantaneous model is part of broader process of “operationalizing” the plant PRA. Additional items in the process include activities related to the development of the risk monitors themselves, and the development and establishment of procedures and governance related to the use of the PRA and risk monitors in applications. This paper looks into the processes and factors requiring consideration when “operationalizing” a nuclear power plant PRA. As well, the paper includes a case study describing the use of an operational PRA to support the decision-making process at Pickering NGS B.