In 1995, the U.S. Nuclear Regulatory Commission (NRC) provided an Option B to Title 10 Code of Federal Regulations (CFR) Part 50, Appendix J, which is a performance-based approach to leakage testing requirements that allows licensees with acceptable test performance history to change surveillance frequencies. Addressed with the performance-based approach are the surveillance frequencies for Type A, B and C tests. The Type A test assesses the overall leakage of containment. The Type B test assesses leakage for containment penetrations. The Type C test assesses leakage for containment isolation valves. At that time, provisions were made for extending the Type A test (integrated leak rate test [ILRT]) frequency from 3-in-10 years to 1-in-10 years.

All nuclear power plants must consider and evaluate external flooding risks such as flash flooding from rain, river flooding, dam failure, hurricane and tsunami. These events challenge off-site power, threaten many on-site plant mitigation components, challenge the integrity of plant structures and limit plant access. Plants must understand the impact of these events in order to fully comprehend and prepare for these plant risks. Existing plant mitigation procedures may not be adequate to deal with these types of events.

A Fire PRA is required to implement plant transition to NFPA 805, as well as to meet NRC Regulatory Guide (RG) 1.200 requirements (i.e., technical adequacy of PRA results for risk informed activities). NFPA 805 is a standard developed by the National Fire Protection Association that provides a risk-informed, performance-based alternative to a plant’s current fire protection program. NUREG/CR-6850 is the NRC-endorsed guidance for developing a Fire PRA that meets the Fire PRA Standard, ANS 58.23.

The Westinghouse Fire Risk Services Team is a one-stop shop for all aspects of nuclear power plant fire protection and fire risk assessment.

Regulatory Guide (RG) 1.200 endorses the American Society of Mechanical Engineers (ASME) consensus standard for internal events probabilistic risk assessment (PRA), which includes a set of minimal requirements for PRA modeling of large early release frequency (LERF). As the use of PRA in the nuclear industry matures, the capability of plant-specific LERF models, particularly those used in regulatory operations, must meet these standards.

Westinghouse provides an independent review of probabilistic risk assessment (PRA) program studies to help customers show that their PRAs meet applicable technical-quality requirements. Per Revision 2 of Regulatory Guide 1.200, PRAs used for risk-informed regulatory applications must meet certain technical adequacy and quality requirements, as determined by the American Society of Mechanical Engineers (ASME) and the American Nuclear Society (ANS) PRA Standard (RA-S-2008).

An internal flooding (IF) risk assessment refers to the quantitative probabilistic risk assessment (PRA) treatment of flooding as a result of pipe and tank breaks inside the plants, as well as from other recognized flood sources. The industry consensus standard for Internal Events Probabilistic Risk Assessment (American Society of Mechanical Engineers/American Nuclear Society [ASME/ANS] RA-Sa-2009) includes high-level and supporting technical requirements for developing an internal flooding PRA (IF-PRA).

The increased focus on probabilistic risk assessments (PRAs) and risk-informed applications by the U.S. Nuclear Regulatory Commission (NRC) has led utilities to expand their PRA model update efforts. Their efforts have initially focused on updating the Level 1 and Level 2 PRA models for the internally initiated events.

Many existing Computer-aided Fault Tree Analysis (CAFTA) and Fault Tree Reliability eXpert (FTREX)-based Probabilistic Risk Assessment (PRA) models have been developed, expanded and updated over several years without a strong focus on the ultimate use of the models.

As the probabilistic risk assessment (PRA) and risk applications quickly become part of the fabric of plant operation and licensing, the time demands on a utility’s current PRA staff are continually increasing to support workday scheduling, outage planning and emergent plant configurations.

Westinghouse drives the global risk industry in delivering well-documented Probabilistic Risk Analysis (PRA) models that effectively balance detail, execution time and the required engineering skill necessary to effectively interpret and communicate the risk insights derived from these models.

The key purpose of an in-service inspection (ISI) is to identify a flaw before it becomes a structural failure. In general, inspections have historically been performed based on such mandated requirements as those for nuclear power plant components in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, insurance requirements or company policy.

For the past 10 years, the nuclear industry and the U.S. Nuclear Regulatory Commission (NRC) have been working together to develop Risk-informed Technical Specifications (RITS) to enhance plant safety and improve plant operations. Of the eight initiatives set forth by the partnership, many are currently available for plant implementation. The remaining initiatives will be available in the near future.

For the past 15 years, the nuclear industry and the U.S. Nuclear Regulatory Commission (NRC) have been working together to develop Risk-informed Technical Specifications (RITS) to enhance plant safety and improve plant operations. Following analysis and methodology development by the industry and subsequent approval by the U.S. NRC, the initiatives set forth by this partnership are now essentially complete and are available for plant implementation. The implementation of the initiatives is facilitated by the Technical Specification Task Force travelers (TSTFs).

For the past 15 years, the nuclear industry and the U.S. Nuclear Regulatory Commission (NRC) have been working together to develop Risk-informed Technical Specifications (RITS) to enhance plant safety and improve plant operations.

For decades, Westinghouse has been supporting the nuclear industry as a full-scope seismic probabilistic risk assessment (PRA) provider, offering capabilities ranging from risk-analysis and risk-informed applications, new plant licensing and Post-Fukushima requirments.

Following the Three Mile Island Unit 2 accident, the U.S. Nuclear Regulatory Commission (NRC) developed a plan (NUREG-1050 – August 1985) to resolve the severe accident generic issue. This plan identified that utility commitment to excellence in risk management, including prevention and mitigation, is key to protection of public health and safety; it also identified the need for new severe accident research.

In response to the events at Fukushima Daiichi, the U.S. Nuclear Regulatory Commission (NRC) issued an interim staff guidance document (JLDISG-2012-01) that places increasing emphasis on analysis of external events including high winds. Additionally, the U.S. NRC issued Regulatory Issue Summary (RIS) 2015-06, “Tornado Missile Protection,” that addresses conformance to a plant’s current site-specific licensing basis for tornado-generated missiles and notes its acceptance of License Amendment Requests using probabilistic risk assessment (PRA) methodologies and computer tools to simulate tornado-generated missiles.