ML20289A678
| ML20289A678 | |
| Person / Time | |
|---|---|
| Issue date: | 10/08/2020 |
| From: | Robert Pascarelli NRC/NRR/DRA |
| To: | |
| Kichline M | |
| Shared Package | |
| ML20289A715 | List: |
| References | |
| Download: ML20289A678 (8) | |
Text
Credit for FLEX in Risk-Informed Licensing Applications Robert Pascarelli Branch Chief, PRA Licensing Branch A Division of Risk Assessment Office of Nuclear Reactor Regulation NEI FLEX Summit Webinar September 2020
Improved Review Efficiency for Risk-Informed LARs 2
- Industry efforts improved review efficiency
- F&O closures reduced number of F&Os submitted
- PRA upgrades identified and peer reviewed prior to submittal
- Incorporation of RAI responses into subsequent LARs
- Public meetings to discuss issues of generic applicability
- Pre-application meetings
- Other areas for improvement and increased dialogue
FLEX Credit in Risk-Informed LARs 3
- Staff has been issuing multi-part RAIs to address all possibilities, including questions on:
- Human Error Probabilities, Failure Rates/Demand Probabilities; PRA upgrade; impact on application
- Public meeting on July 29, 2020 discussed staff information needs regarding FLEX
- Increased review efficiency needed in this area
Guidance on Key Assumptions and Sources of Uncertainty 4
comparison of the PRA results with the acceptance guidelines must be based on an understanding of the contributors to the PRA results and the impacts of the uncertainties, both those that are explicitly accounted for in the results and those that are not.
RG 1.174 NRC reviewer..
[will].. focus their review on key assumptions and areas identified by peer reviewer as being of concern
[i.e., F&Os]
RG 1.200 Guidance on Treatment of Uncertainties Associated with PRAs NUREG 1855
- Credit for FLEX in PRA may impact the regulatory decision, therefore may be a key assumption or source of uncertainty for an application
- Identification and evaluation of uncertainties is important for TSTF-505 and 50.69
- Allow licensees to approach acceptance guidelines, or
- Reliance on importance measures, which are influenced by either conservative and non conservative assumptions in the PRA FLEX Credit Review in LARs 5
PRA Configuration Control 6
RG 1.200 requires PRA Configuration Control process to provide confidence that the PRA adequately represents the as-built, as-operated plant.
- Incorporation of FLEX in PRA consistent with guidance Is incorporation of FLEX a PRA Upgrade or Update?
- Plant specific arguments
- PRA Upgrade definition
- RG 1.200 Rev 2: a change in capability that impacts significant accident scenarios or results
- Upgrades require focused-scope peer reviews
- Peer reviews provide for independent expert review of licensees implementation; may be beneficial to assist staffs review
Potential Paths Forward for Risk Informed Licensing Risk Informed LAR Review No or minimal impact Staff may perform a cursory review of FLEX credit More than minimal impact Detailed, plant specific review; potentially through audit Open to other alternatives to be explored
?
NRC Generic Review Can be complex review; all plants and applications 7
Conclusions
- Staff will continue to review FLEX credit in risk-informed applications
- Generic review of FLEX credit would benefit both NRC and industry 8