The ASME PSA Standard and Its Role in Risk Informed Regulation

Abstract

The nuclear industry has been aggressively pursuing risk-informed regulation for the past seven years. In this pursuit, the Nuclear Regulatory Commission (NRC) has established a basic framework for reviewing and granting risk-informed regulations. Focused regulatory guides have been specifically prepared in the areas of Plant Technical Specifications, In-Service Testing, In Service Inspections and Graded Quality Assurance. While these regulations have not supplanted traditional deterministic regulations, they have been used to support focused changes to the plant design basis. As the industry continues to mature the use of PSA information in day to day plant operations will grow. Today, risk insights are required by federal regulation for all plant maintenance activities. In addition, the regulator reserves the right to include consideration of risk in applications where the outcome could have a significant impact on risk. Despite, the major strides made in development and use of risk information, the industry and the regulator were operating without an agreed to PSA standard. Over the past three years the ASME has formed a committee of stakeholders, both commercial and regulatory, to develop a workable standard for the development and utilization of PSA data in the nuclear industry. The ASME PSA standard has recently been issued. The current standard has been developed to support licensing applications and is focused on the development and use of the Level 1PSA and the calculation of the Large Early Release Frequency (LERF). The ASME standard is unlike most standards in that it is tiers, and includes guidance for using results when specific items in the standard are not in complete compliance with specific standard elements. The tiers included in the standard are reflective of the level of detail in the PSA elements. The ability to use PSAs with many elements acceptable only at the lowest tier will be more limited than for more sophisticated PSAs and therefore, applications may be limited in scope and would likely involved strong deterministic support as well. As PSA tiers increase the reliance of the decision on the PSA may increase. The acceptability of the PSA elements is established via peer review process. It is the intent of this panel discussion to explore the implications of the recently released ASME PSA standard, and other focused standards under development on the nuclear industry and the role of the ASME standard in the associated regulatory process. The panelists will explore expectations of the industry, needs of the regulator and challenges of the PSA peer review process.