Optimizing PRA Models and Operations

Westinghouse uses experience to deliver services for PRA/PSA model and operations efficiency. PRA/PSA model development, optimization and integration, and maintenance/update support.

Internal Events

Our team has performed modeling and provided training and consultation on model building techniques, methods and other risk modeling items to consider and has gained extensive experience through partnerships and new plant model development for Level 1, Level 2 and low power and shutdown conditions. With the end in mind, we can help construct or optimize the Internal Events model to serve as a backbone for all hazard PRA models.

Internal Flood

Our team capitalizes on experience in internal flooding methods to support model building or consultation support.

We have performed full scope IF-PRAs for several nuclear power plants, supporting the original development of the Electric Power Research Institute (EPRI) guidelines for development of an IF-PRA, that has been exercised in all its tasks, from the initial IF-dedicated walkdowns to the final model and quantification with different PRA code.

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Internal Fire

Our team capitalizes on experience in internal fire methods to support a wide range of services including model building or consultation support. We can perform detailed fire modeling to provide a realistic fire risk assessment in key fire compartments at the plant. Westinghouse engineers are qualified users of all mainstream zone and computational fluid dynamics fire modeling software (e.g., CFAST, MAGIC, and FDS). In addition, Westinghouse has developed and validated our own multiple compartment fire analysis code, FATE. Westinghouse Fire PRA experience in time-consuming tasks, such as plant walkdown, and industry lessons-learned can be leveraged to combine walkdowns for several tasks to maximize overall efficiency in a cost-saving manner. Our team can also support related fire services including safe shutdown analysis, NFPA-805 and fire protection.

We have performed numerous full scope Fire PRAs for both domestic and international nuclear power plants. Westinghouse has fire model experience with 2, 3, and 4 loop designs as well as BWR and new reactor (AP1000 and ABWR). We have experience with the methodology of NUREG/CR-6850 and supplemental guidance, NFPA-805 fire protection program, ASME/ANS standard, RG 1.200, as well as peer review and regulatory review experience.


Our team capitalizes on seismic experience globally to support utilities in seismic evaluations. Our large spectrum of skills allows for a single integrated team to address every single aspect of a seismic PRA, from coordination of the seismic hazard development to the development of detailed finite element models for buildings and structures; from walkdowns by experienced Seismic Qualification Utility Group (SQUG) qualified engineers to the development of structural, component and relay fragilities.

We have developed several peer-reviewed S-PRA models for plants with different seismic hazards characteristics, including the very first Seismic PRA successfully peer reviewed in the United States against the modern ANS/ASME PRA Standard. These S-PRA models were developed using guidance from EPRI implementation guideline that we helped develop and meets the requirements of the ASME/ANS PRA standards.

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External Hazards

Our team uses vast experience in external hazards and high winds to support the market of model development or consultation.

We have supported one of the most extensive external flooding risk evaluations in the industry (Fort Calhoun Power Station) and has been involved with EPRI and NRC in developing guidance for external flooding hazard evaluations, fragility assessment for penetration seals and PRA modeling, including the unique human factor elements associated with long term actions in case of flooding.

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Spent Fuel Pool

We have provided Spent Fuel Pool PRAs addressing both the seismic hazard and the spent fuel pool cooling systems risk assessments.

Low Power and Shutdown

Our team has extensive experience performing LPSD PRA studies to meet customer needs and industry requirements.

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Peer Reviews

Our team has extensive experience with peer reviews including through the Pressurized Water Reactors Owners Group (PWROG). In addition to peer review support, we provide self-assessment and independent review support.

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Severe Accident Analysis

Westinghouse has extensive Severe Accident Management Guidance (SAMG) experience and is well equipped to support customer needs ranging from full updates to reflect updated industry guidance, gap assessments for training/drills, development of accident scenarios and training support.

Westinghouse has developed plant-specific SAMG programs as well as supported development of generic industry SAMG guidance.

Specialty Risk Products

WRAP: Westinghouse continues to develop Innovative tools to streamline the development and maintenance of the PRA models supporting Risk-Informed Applications. Among the latest is WRAP, which organizes the immense amount of physical and operational data that is then used to generate all, or a focused portion of the PRA model.

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Multi Unit PRA: Westinghouse can perform multi-unit PSA assessments. As the vast majoring of NPPs worldwide have at least two units, there is the ability to model site wide events and provide necessary regulatory alignment post-Fukushima.

Digital I&C PRA Modeling: The Digital I&C PRA modeling skill is a specialized skill related to PRA systems modeling that addresses unique features associated with digital I&C systems.

Industrial Risk Assesment: This service primary focuses on generic problem solving capabilities and the ability to employ and/or adapt a variety of risk-based tools to implement solutions and fit the individual needs of the specific application at hand.

Fault Tree Target Set Analysis (FTTSA): PRA logic associated with area events (i.e., flood and fire) is used as starting point and appropriately manipulated to assess/identify target sets.

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Risk-Informed Design: Risk-Informed design is a combination of skills that uses numerous elements in from Probabilistic Risk Assessment to support design phase as opposed to supporting operation for operating reactors.