ML21167A161
| ML21167A161 | |
| Person / Time | |
|---|---|
| Issue date: | 06/16/2021 |
| From: | Kristy Bucholtz, Antonios Zoulis NRC/NRR/DRA/APOB |
| To: | |
| Vasavada S | |
| Shared Package | |
| ML21167A163 | List: |
| References | |
| Download: ML21167A161 (8) | |
Text
PRA and Risk Insights in 10 CFR 50.59 Antonios Zoulis Branch Chief, Division of Risk Assessment Kristy Bucholtz Reliability and Risk Analyst 1
Background - RG 1.187
- Regulatory Guide (RG) 1.187, Rev. 1 endorses industry guidance on implementation of 10 CFR 50.59 requirements o NEI 96-07, Rev. 1, Guidelines for 10 CFR 50.59 Implementation
- NRC did not endorse reference documents in NEI 96-07, Rev. 1 nor were the examples found to be applicable for all licensees.
- Licensees are responsible for ensuring that an example is applicable to its circumstances before implementing the guidance.
2
Background - 10 CFR 50.59
- In the 1999 Statement of Considerations for 10 CFR 50.59, commenters
- requested quantitative standards and guidance for using risk insights or PRA to determine when a more than minimal increase in probability has occurred, and
- thought that values for changes in CDF and LERF in RG 1.174 might be used.
3
Background - 10 CFR 50.59
- In the 1999 Statement of Considerations for 10 CFR 50.59, the Commission
- Stated RG 1.174 was developed for the purpose of guiding changes to the licensing basis where the NRC staff was reviewing and approving the change, not for changes made under § 50.59.
- Concluded that if use is to be made of PRA in § 50.59, more fundamental changes to the rule would be necessary to provide a coherent set of requirements, in that § 50.59 deals with design basis events, and RG 1.174 deals with risk including that from severe accidents beyond the design basis.
4
Inspection Manual Chapter 0335
- NRC working group used public engagement, agency experts, and agency-wide collaboration to develop IMC 0335 o Derived from review of several existing documents (e.g., NEI 96-07, existing Part 9900 Guidance, and Statement of Considerations for the rule) o Provides guidance to inspectors regarding use of PRA and risk insights in 10 CFR 50.59 evaluations 5
IMC 0335 PRA and Risk Insights
- Consistent with the Commissions statements supporting the final 10 CFR 50.59 rule.
- While the resultant CDF and LERF from the PRA are not acceptable as the sole basis to inform the licensees 10 CFR 50.59 evaluation, it is acceptable for licensees to use reasonable engineering practices, engineering judgement, and PRA techniques, as appropriate, to inform 10 CFR 50.59 evaluations with respect to more than a minimal increase.
6
Potential Path Forward
- In the 1999 Statement of Considerations, the Commission acknowledged that it may be possible to develop guidance for accident frequency that could be used in a quantitative sense to judge minimal increases
- Specifically, values developed as part of the revised oversight process could be considered, so that the increase is minimal, if the resultant likelihood of occurrence remains well within the acceptable ranges given for initiating events.
- The NRC staff would like to determine the level of interest in pursuing this option?
7
Questions?
8