Integration of Risk Insights Into Nuclear Power Plant Operations

Today’s nuclear plant operator is challenged to safely operate a complex power plant while prudently managing the business aspects with efficiency. Risk insights provide a ready tool to aid today’s operators in effectively performing both of these sometimes contradictory tasks with a sound basis. While plants possess and maintain Probabilistic Risk Assessment (PRA) models, other regulatory applications are readily available to aid the nuclear operator. Some of these tools include 10CFR 50.69 Risk-informed Categorization and Treatment of Structures, Systems, and Components for Nuclear Power Reactors, Industry Initiative 4(b) Risk Managed Technical Specifications, and Industry Initiative 5(b) Risk-informed Surveillance Test Intervals. This paper will introduce each of these risk-informed tools and will discuss practical applications of these insights at the South Texas Project nuclear power plant. These insights are readily translatable to other nuclear power facilities. 10CFR 50.69 permits a risk-informed categorization of selected structures, systems, and components. For components determined to be Low Safety Significant, many of the current regulatory controls can be reduced while maintaining reasonable confidence that these ‘Low-ranked’ components continue to perform their design functional requirements. South Texas Project was the industry’s proto-type pilot for this effort. Initiative 4(b) is a risk-informed, configuration-based approach to managing Technical Specification allowed out of service times. The limiting, deterministic allowed outage times are replaced with a Configuration Risk Management Program which uses risk threshold values to determine the length of time a Technical Specification piece of equipment can remain out of service. An imposed back-stop of 30 days is used to limit the allowed outage time. This approach was approved for South Texas Project in July 2007, and South Texas Project was the industry pilot plant for this effort. Initiative 5(b) is a risk-informed approach to Technical Specification surveillance test intervals. This approach allows surveillance test intervals to be removed from Tech Specs and placed in an owner-controlled program. Once relocated, a blending of probabilistic and deterministic insights is used to assess proposed extensions of surveillance test intervals. Once implemented, a feedback process is relied upon to validate the acceptability of the revised testing interval. This approach was piloted by the Limerick Nuclear Station, and South Texas Project submitted a request in October 2007 to the NRC to pursue this initiative. The above risk insights have proven very effective at South Texas Project, and could aid other nuclear operators in making well-founded, informed decisions. Risk insights also allow a Station’s limited resources to be focused on those activities and equipment which are of greatest safety significance. These insights are valuable for current licensees, and may be very beneficial to apply toward new nuclear construction.