Probabilistic Risk Assessment for Nuclear Plants

Probabilistic risk assessment (PRA) methods deal with the low frequency, high impact hazards identified in the operation of nuclear facilities.

Nuclear industry PRA methods have become an invaluable tool to quantify safety and economic risk and to answer “what if?” questions.  Intertek Nuclear performs independent PRA reviews for utilities to assess the significance of off-normal situations.

The technical requirements for the design, operation, and maintenance of a nuclear generating plant are spelled out in Title 10 of the Federal Regulations (10CFR). How these requirements are met is described in the Safety Analysis Report (SAR) for each nuclear facility. These technical requirements are based on traditional engineering methods using safety factors and levels of conservatism that have been proven by practice.

As probabilistic risk assessment methods have matured and computing power has increased, the use of probabilistic methods to address the significance of hazards has become routine, so much so that the regulators now use a risk informed approach.

The concept of risk with a nuclear power plant involves three questions:  

• What could go wrong? (identification of a hazard)
• How likely is it? (frequency)
• What are the consequences? (impact both economic and societal)

Risk is the product of frequency and consequences; a probabilistic risk assessment defines these parameters for each identified hazard. The power of the PRA is increased by the ability to quantify uncertainty and to evaluate the financial value of options to reduce risk. Risk reduction methods are based on reducing frequency (by proactive measures such as inspections and replacement) or by reducing consequences by mitigating measures.

Intertek Nuclear performs independent PRA reviews for utilities and has utilized existing plant PRAs to assess the significance of off-normal situations (defective valve parts for example). By connecting the impact of defective parts, components or systems to the PRA, the action plan for repair or replacement can be developed in a schedule that includes the importance to plant safety.

Intertek Nuclear has also used PRA methods for the design and operation of other high asset value systems such as deep sea pipelines and in the oil and gas industry.

Contact us to see how Intertek can help your organization with Probabilistic Risk Assessment for Nuclear Plants.