ML21085A594
| ML21085A594 | |
| Person / Time | |
|---|---|
| Issue date: | 03/30/2021 |
| From: | Stutzke M NRC/NRR/DANU |
| To: | Nuclear Energy Institute |
| Williams D | |
| References | |
| Download: ML21085A594 (18) | |
Text
NLWR PRA Acceptability Public Meeting March 30, 2021 1
Background
- NRC staff issued draft White Paper in January 2021- Demonstrating the Acceptability of Probabilistic Risk Assessment Results Used to Support Advanced Non-Light Water Reactor Plant Licensing - ML21015A434
- NEI provided feedback at February 23, 2021 public meeting - ML21055A732 2
Items for Regulatory Guide Section B, Discussion
- Interface with the Parts 50/52 alignment rulemaking
- Docket NRC-2009-0196; RIN-3150-AI66
- Use of assumptions in lieu of detailed design information for CP PRA
- Timing of OL PRA (after plant construction is essentially complete)
- Interface with the Part 53 rulemaking
- NRC-2019-0062; RIN-3150-AK31
- Interface with the graded PRA initiative:
- Develop regulatory position by early May
- Incorporate into ARCAP or develop a stand-alone RG
- Interface with the graded SAMDA analysis initiative for microreactors
Response to NEI Comments Provided During 2/23/2021 Public Meeting (1 of 15)
NEI Comment Staff Response Slide 3, 3rd bullet Will clarify that the draft white paper and the Stated document purpose should reflect that trial-use RG apply to commercial power the existing commission policy and rules reactors.
related to PRA are specific to power reactors and are not applicable to non-power reactors.
Slide 3, 4th bullet 10 CFR Part 51 applies to advanced reactors, References to SAMDAs should be eliminated including NLWRs. The staff is exploring ways to due to lack of applicability of SAMDAs for screen out SAMDAs for microreactors without advanced technologies. going through the entire process as described in NEI 05-01A.
Slide 3, 5th bullet The staff proposes the new term and initialism References to Level 3 PRA should be Comprehensive Probabilistic Radiological Risk eliminated. This term is not appropriate for an Assessment (CPRRA) in lieu of Level 3 PRA.
ANLWR design.
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (2 of 15)
NEI Comment Staff Response Slide 3, 6th bullet
- PRA may be developed using either relative Expectations for relative risk significance or absolute risk significance criteria.
criteria should be removed.
- PRA developer has flexibility in selecting which risk target(s) to use when determining absolute risk significance.
- It is anticipated that NLWRs will have very low risks.
- The staff is concerned that only a few PRA items will be reported as absolute risk significant. Such a result provides limited insight into (1) what PRA items actually control the risk and (2) how to tailor the staffs review process.
- NEI 18-04, Rev. 1, p. 29: Hence, it is appropriate to evaluate risk significance not only on a relative basis but also on an absolute basis.
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (3 of 15)
NEI Comment Staff Response Slide 4, 1st bullet
- Refer to the Part 50/52 alignment No clear basis for expectation of PRA at rulemaking (Docket NRC-2009-0196; RIN-Construction Permit stage 3150-AI66).
- Detail is not available at this time
- Will provide discussion (i.e., links) to
- No safety finding is made at this stage, PRA related ongoing regulatory activities in is not needed Section B of the trial-use RG on NLWR PRA acceptability.
Slide 4, 2nd bullet The staff intends to endorse the screening Screening criteria from the standard should be criteria. Note that the staff may include endorsed as well. clarifications, qualifications, exceptions, or additions in any proposed endorsement.
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (4 of 15)
NEI Comment Staff Response Slide 4, 3rd bullet
- The draft staff white paper reflects the Expectations for timing and scope of peer staffs current interpretation of the NLWR reviews PRA standards requirements.
- Several listed stages will not have PRAs The discussion of peer reviews is aligned suitable for peer review with licensing submittals.
- Scope should be according to PRA
- NLWR applications must demonstrate the availability and changes, not by design acceptability of their PRAs.
The trial-use RG on NLWR PRA acceptability will provide one (but not the only) acceptable approach.
- How will the staff determine the acceptability of a PRA that is not suitable for peer review?
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (5 of 15)
NEI Comment Staff Response Slide 5, 1st bullet
- Agreed. This discussion needs to be Discussion of white paper revealed need for coordinated with the Part 53 rulemaking additional dialogue in several key areas outside and the Part 50/52 alignment rulemaking.
the scope of the paper itself
- Will provide discussion (i.e., links) to
- What PRA means for various technologies related ongoing regulatory activities in
Standard
- Need for durable, visible guidance from NRC Slide 5, 2nd bullet Agreed.
Common understanding critical to providing context of white paper 8
Response to NEI Comments Provided During 2/23/2021 Public Meeting (6 of 15)
NEI Comment Staff Response Slide 6, 1st bullet
- The only purpose of NEI 18-04 is to provide Page 7: For ANLWR applications that are based an acceptable way of selecting licensing on the LMP guidance, the PRA is used to select basis events, classifying SSCs, and licensing basis events, classify systems, evaluating defense-in-depth.
structures and components (SSCs), and to
- The staff agrees that NEI 18-04 is not the inform the defense-in-depth evaluation. only acceptable way for doing so.
- is should be may be as this need not be required 9
Response to NEI Comments Provided During 2/23/2021 Public Meeting (7 of 15)
NEI Comment Staff Response Slide 6, 2nd bullet Will clarify as follows (adapted from RG 1.200, Page 8: Plant representation and PRA Rev. 3):
configuration control
- The listed definition doesnt address PRA Plant representation and PRA configuration configuration control. Suggest eliminating. control: Plant representation is defined in terms of how closely the PRA represents the plant as it is designed, built, and operated. In general, PRA results used to support an application must be derived from a PRA model that represents the as-designed (as-to-be-built), as-built (as-to-be-operated), and as-operated plant to the extent needed to support the application. Consequently, the PRA is maintained and upgraded, where necessary, to ensure it represents the as-designed (as-to-be-built), as-built (as-to-be-operated), and as-operated plant.
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (8 of 15)
NEI Comment Staff Response Slide 7, 1st bullet Will clarify as follows:
Page 8: The NRC staff expects that a PRA that supports implementation of the LMP guidance The NRC staff expects that a NLWR PRA that or other voluntary risk-informed applications supports implementation of the LMP guidance (such as implementation of 10 CFR 50.69 for or other voluntary risk-informed applications applicants that do not use the LMP guidance), (such as implementation of 10 CFR 50.69 for will have an increased level of detail and plant applicants that do not use the LMP guidance),
representation. will have an increased level of detail and plant
- Some ANLWRs will have a simplified safety representation as compared to a NLWR PRA case so additional detail (relative to LWRs) that does not support implementation of the may not be necessary. This sentence should LMP guidance or other voluntary risk-informed be eliminated. applications.
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (9 of 15)
NEI Comment Staff Response Slide 8, 1st bullet
- The staff understands that the NLWR PRA Page 10: Discussion on CDF and LERF standard provides requirements for
- The ANLWR PRA standard is not organized developing a CPRRA.
- The draft staff white paper discusses the
- These references are not appropriate for difficulties involved in adapting this white paper/regulatory guidance. intermediate risk metrics used for LWRs to
- The PRA owner may define and use core NLWRs. This discussion should be of damage, but not all will. interest to NLWR applicants who are
- Risk integration and risk significance criteria contemplating the development of a PRA require quantification of event sequence that is less than a CPRRA.
consequences
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (10 of 15)
NEI Comment Staff Response Slide 8, 2nd bullet
- See response to Slide 8, 1st bullet.
Page 10: Discussion on LRF
- Interestingly, SRM-SECY-89-102
- LRF and LERF are intentionally not used in (ML12251A496) states that the Large the standard and should not be used here. Release Guideline relates to all current as
- Existing definitions of LRF and LERF are well as future designs. This SRM qualitative and difficult to apply to NLWRs specifically mentions LWRs, LMRs, and HGTRs.
Slide 9, 1st bullet
- Consistent with the discussion provided in Page 11: Discussion on fire LPSD POSs SRP Chapter 19.0, Final Rev. 3 (December
- There is insufficient technological 2015), pp. 19.0-23 and 19.0-24, the staff advancement to support development of expects NLWR PRAs to address internal fires supporting requirements on this in the that may occur during LPSD.
standard. It is unclear what the purpose of
- The use of bounding, conservative, and screening analyses may be appropriate.
- The NRC is considering the need to initiate research into LPSD fire PRA.
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (11 of 15)
NEI Comment Staff Response Slide 9, 2nd bullet The staff interprets the NLWR PRA standard as Discussion on bounding site requiring the use of site-specific information
- An application should only need to provide (e.g., external hazards, meteorology) once the enough siting information to demonstrate site has been selected. For example, see the that the site is bound by the bounding site table provided in Section 3.3.2.
analyses performed.
Slide 10, 1st bullet 10 CFR Part 51 applies to advanced reactors, Page 12: Risk metrics that support the including NLWRs. The staff is exploring ways to evaluation of SAMDAs, such as population dose screen out SAMDAs for microreactors without risk (person-rem per plant-year) and offsite going through the entire process as described economic risk ($ per plant-year). in NEI 05-01A.
- SAMDAs are likely not in the scope for many ANLWRs and this is not an appropriate expectation 14
Response to NEI Comments Provided During 2/23/2021 Public Meeting (12 of 15)
NEI Comment Staff Response Slide 10, 2nd bullet Revisions to the PRA should be reflected in Page 13: Commercial operations stage: The periodic FSAR revisions, as required by 10 CFR plant accrues operating experience; the PRA 50.71(h)(2) for COL holders. The Part 50/52 reflects the as-built, as-operated plant alignment rulemaking will add a similar including plant-specific operating experience. requirement for OL holders.
- It is unclear what is meant by this. Is there an expectation that the PRA will be resubmitted?
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Response to NEI Comments Provided During 2/23/2021 Public Meeting (13 of 15)
NEI Comment Staff Response Slide 11, 1st bullet
- Will coordinate with the Part 50/52 Page 13: OL application stage: The plant has alignment rulemaking.
been constructed and is ready to begin pre-
- Will provide discussion (i.e., links) to operational testing; the PRA generally related ongoing regulatory activities in represents the as-built and as-to-be-operated Section B of the trial-use RG on NLWR PRA plant but does not reflect plant-specific acceptability.
operating experience.
- The plant has not necessarily been constructed at the OL stage. The OL cannot be issued until the plant is largely constructed.
o A defined time prior to fuel load could be a better expectation.
- In this sentence, as-built should be as-to-be-built 16
Response to NEI Comments Provided During 2/23/2021 Public Meeting (14 of 15)
NEI Comment Staff Response Slide 12, 1st bullet 10 CFR 50.71(h)(2) requires COL holders to Page 16: Type 5 SRs become applicable when maintain and upgrade the PRA every four plant-specific operating experience is first years. The Part 50/52 alignment rulemaking incorporated into the PRA; Type 4 SRs become will add a similar requirement for OL holders.
not applicable
- Unclear on what the regulatory standing of this is Slide 12, 2nd bullet See response to Slide 3, 6th bullet.
Page 17: Discussion on use of relative and absolute criteria.
- Standard gives flexibility for use of either criteria; requiring both types of criteria was never considered in the standards development or use 17
Response to NEI Comments Provided During 2/23/2021 Public Meeting (15 of 15)
NEI Comment Staff Response Slide 13, 1st bullet Agreed, as stated in the draft staff white paper.
Page 18: Reference to Appendix B The staff expectations for PRA quality control
Slide 13, 2nd bullet Agreed. The staff is pointing out that TI-CAP is Page 20: The industry-led technology-inclusive expected to provide an acceptable approach content of application project (TI-CAP) is for documenting PRA results, should an developing proposed content for specific applicant decide to use it.
portions of the safety analysis report (SAR) that would be used to support an advanced reactor application. The TI-CAP portion of the SAR will be informed by the guidance found in the LMP guidance (NEI 18-04).
Change would to could -TI-CAP should not be required to be used by applicants for advanced reactor licenses 18