ML22102A206

Comment (1) of Frances Pimentel on Design-Basis Floods for Nuclear Power Plants

ML22102A206
Person / Time
Site:	Nuclear Energy Institute
Issue date:	04/08/2022
From:	Pimentel F Nuclear Energy Institute
To:	Office of Administration
References
87FR10260 00001, NRC-2022-0037
Download: ML22102A206 (10)

Text

4/12/22, 9:13 AM blob:https://www.fdms.gov/aea6afa2-abcb-40b2-ad21-db2ffb8f092c SUNI Review Complete Template=ADM-013 As of: 4/12/22 9:13 AM E-RIDS=ADM-03 Received: April 08, 2022 PUBLIC SUBMISSION ADD: Edward ODonnell, Bridget Curran, Mary Neely Status: Pending_Post Tracking No. l1q-l0ss-v6mp Comment (1)

Publication Date: 2/23/2022 Comments Due: April 11, 2022 Citation: 87 FR 10260 Submission Type: Web Docket: NRC-2022-0037 Design-Basis Floods for Nuclear Power Plants Comment On: NRC-2022-0037-0001 Design-Basis Floods for Nuclear Power Plants Document: NRC-2022-0037-DRAFT-0002 Comment on FR Doc # 2022-03791 Submitter Information Email: atb@nei.org Organization: Nuclear Energy Institute General Comment See attached file(s)

Attachments 04-08-22_NRC_ Industry Comments on DG-1290 -R1 blob:https://www.fdms.gov/aea6afa2-abcb-40b2-ad21-db2ffb8f092c 1/1

FRANCES PIMENTEL Senior Project Manager Risk and Technical Support 1201 F Street, NW, Suite 1100 Washington, DC 20004 P: 202.739.8132 fap@nei.org April 8, 2022 Office of Administration Mail Stop: TWFN-7-A60M U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 ATTN: Program Management, Announcements and Editing Staff Project Number: 689

Subject:

NEI Comments on Draft Regulatory Guide DG-1290, Design-Basis Floods for Nuclear Power Plants, Docket ID NRC-2022-0037 Subm itted via regulations.gov

Dear Program Management,

Announcements and Editing Staff, The Nuclear Energy Institute (NEI) 1, on behalf of our members, appreciates the opportunity to provide comments on the subject Draft Regulatory Guide DG-1290, Design Basis Floods for Nuclear Power Plants.

The purpose of this letter is to provide the attached comments which recommend several changes to improve clarity and consistency on the recommended approaches, methods, and analysis this guidance provides.

The regulatory analysis associated with this revision concludes that this update should enhance nuclear power plant safety by providing up-to date guidance and information on determining the effects of severe flooding on nuclear power plants. While the proposed revision does provide reference to updated information, the guidance on design basis flood estimation approaches is very general and lacks specific application details that would enhance the effectiveness of the Regulatory Guide as a useful tool to both end users and the NRC. Additionally, the industry is concerned that the absence of details regarding the approaches and methods discussed in the revision inhibits the enhancement of regulatory certainty in this subject area.

1 The Nuclear Energy Institute (NEI) is responsible for establishing unified policy on behalf of its members relating to matters affecting the nuclear energy industry, including the regulatory aspects of generic operational and technical issues. NEIs members include entities licensed to operate commercial nuclear power plants in the United States, nuclear plant designers, major architect and engineering firms, fuel cycle facilities, nuclear materials licensees, and other organizations involved in the nuclear energy industry.

Program Management, Announcements, and Editing Staff April 8, 2022 Page 2 For example, the discussion in Appendix A on climate variability, climate change, and sea level rise. This section provides details with respect to sea level rise; however, little guidance is included identifying expectations as to which approaches may be preferred (or acceptable) and which hazards, other than storm surge, should be evaluated. To ensure more consistent treatment of climate change impacts, the appendix should include a discussion based on the current knowledge of which external flood hazards would be significantly impacted by climate change and how climate change extrapolations should be treated.

This is just one example of several provided in Attachment 1 that recommend providing additional detail on ways the NRC expects applicants and licensees to apply the updated information presented in this revision.

We appreciate the NRCs effort in developing this draft guidance and encourage your consideration of all stakeholder comments prior to finalizing this draft Regulatory Guide. We trust that you will find these comments useful and informative as you finalize the draft. Please contact me at fap@nei.org or (202) 739-8132 with any questions or comments about the content of this letter or the attached comments.

Sincerely, Frances A. Pimentel Attachment c: Joseph Kanney, RES/DRA/FXHAB, NRC Edward ODonnell, RES/DE/RGPMB, NRC

Attachment 1 Comments on Draft Regulatory Guide DG-1290, Design Basis Floods for Nuclear Power Plants Section Comment/Basis Recommendation

1. Overall message There are some places that hint at a This DG would benefit from explicitly nuclear power plant design that is not stating that a purely deterministic challenged by a flood event not needing approach that assumes a worst-case to perform the detailed analyses flood condition should not need to described in this DG. This DG would provide the NRC staff with the benefit from explicitly stating that a rigorous, site-specific analyses purely deterministic approach that described in this DG.

assumes the entire facility is under water should not need to provide the NRC staff with the rigorous, site-specific analyses described in this DG.

2. B. Analysis Approach The document states that an acceptable This statement conflicts with NRCs (Page 7) framework for probabilistic assessments planned endorsement of the is not currently available nor are ANS/ASME PRA standard that standards acceptable to NRC staff requires PFHA be used to deal with available to review such a probabilistic flooding. Since the standard requires analysis. Accordingly, Probabilistic Flood it, NRC should be able to describe Hazard Assessments (PFHA) will be what is needed or NRC should not considered only on a case-by-case basis endorse that part of the standard by NRC staff. calling for PFHA.

3. B. Analysis Approach The document notes: This guide does NRC should consider guidance on (Page 7) not provide specific guidance on how probabilistic approaches could probabilistic methods for developing be used for combined events.

quantitative estimates of flooding hazards, however, the DG further states The staff expects that either probabilistic or frequency-based estimates, or some combination of the two, will be needed to inform the analysis of combined events.

Furthermore, the staff notes that a framework or Standard for review of these approaches does not exist. This is noted to be of particular importance in the low frequency tails (< 10-4/yr) of the distribution.

4. B. Analysis Approach NRC notes Appendix A to this guide The discussion in App A provides no (Page 8) further discusses PFHA. significant guidance as to what a PFHA should contain and expectations with regards to 1

Section Comment/Basis Recommendation treatment of uncertainty. Please provide more details on how a probabilistic approach could be used for combined events.

5. B. Flood-Causing While in agreement with how a vast Update the document to detail Mechanisms. majority of Flood Hazard Reevaluations whether there are any acceptable Flooding Caused by (FHRs) were performed for Local Intense circumstances or conditions to which Local Intense Precipitation (LIP), criteria for the NRC staff would consider the site Precipitation (Page 8 functionality of a sites drainage drainage or stormwater management to 9) and C.3.a network/stormwater management system system to be functioning or partially Flooding Caused by should be provided. Mechanisms could functioning during an LIP event.

Local Intense include regular maintenance and Precipitation (Page inspection are performed as part of a

17) and C-1. storm preparedness operating General procedures.

Considerations (Page C-1 to C-2)

6. B. Flood-Causing The document notes that wind-generated While agreed that a distant storm Mechanisms. Wind- wave activity may yield a significant may be the bounding scenario, it Generated hazard independent or coincident with would be helpful to place some Associated Wave severe hydrometeorological conditions, bounds or framework, at least Effects (Page 12) specifically that a distant storm could conceptually, on the types and yield more severe wave action than a locations of events that must be local storm event. considered as part of the wave effects analysis for coastal locations.

7. C.2.a The current value used as the annual This value is more conservative than probability of exceedance for the even the seismic values in some reasonableness of combined event ways, and there is less data available flooding scenarios (1E-6) is unreasonably for flooding in many locations.

low and does not have an associated Instead, NRC should focus on the justification. potential for core damage (or equivalent for designs using other metrics). For example, a flood with given a mean annual frequency of E-5 per year with a CCDP of 0.1, with the CCDP crediting reliability of event mitigation, should be acceptable as this is consistent with other regulatory approaches to external hazards, e.g., seismic. Similar consideration of event mitigation can be included in identifying the mean 2

Section Comment/Basis Recommendation annual frequency for designs that use metrics other than core damage.

8. C.2.b The Extreme Storm Data Compilations Recognize that when a technically section does not recognize the value accurate, publicly available data these data sources have or how they source is up to date for a region, it should be included in identifying flood can be employed to characterize potential. Further, site specific flooding in the region. Further, characterization of flood potential should recognize that some advanced NPPs not need to be included if a reactor may not be challenged by flooding.

design is not challenged by flooding.

9. C.2.c. Nonstationary In discussion of sea level rise, it is stated The document should further Effects (Page 16) Additional site-specific analyses will elaborate on when site-specific need to support less conservative analysis may differ from design-basis estimates described in USGCRP Appendix flood analyses (which are requested A. to follow the USGCRP Appendix A methodology). The document should detail the basis for an acceptable less conservative sea level rise estimate.

10. C.3.d Flooding The process detailed for hurricane Provide a better definition and/or Caused by Storm parameter selection in areas where framework for storm parameter Surges, Seiches, and limited historical data is available mirrors selection in areas with a deficient Tsunamis (Page 19- very close a probabilistic-style evaluation, historical record that may not be

20) both in consideration of the representative of worst-case interdependency of meteorological situation(s). Further elaborate on the conditions and storm surge-related data sampling noted for synthetic effects of the storms. However, there is storm simulations. What suite of no detailed guidance provided about how synthetic storms would NRC staff find to approach the selection other than the acceptable for an PMH evaluation?

use of current state-of-the-art knowledge of storm phenomenology which is ambiguous.

11. C.3.h Combined The NRC staff currently uses an average A more complete discussion of Events (Page 22) annual probability of exceedance of less acceptability of frequency methods than 1 x 10-6 as a metric to evaluate the should be considered in the final reasonableness of combined flooding version of the DG.

event scenarios. However, guidance on formal PFHA approaches needed for Given the significance of the metric it consistent treatment of combined events would seem appropriate for NRC to is lacking. Therefore, the NRC will assess provide guidance to help the analyst the reasonableness of qualitative and develop an acceptable approach and 3

Section Comment/Basis Recommendation quantitative probability estimates for presentation and, in particular, combined events on a case-by-case identify pitfalls.

basis.

12. A-3. Non- In terms of coastal erosion effects, the Please include recommendations or a stationarity: Climate document cites a study for SLR effects on methodology for erosional effects Variability, Climate coastal erosion, both for cliff- and dune- (with and without SLR) for sites that Change, and Sea backed coastlines. However, many east may not be able to directly use Level Rise (Page A-2 coast power plant sites do not fit into published methods for classical cliff-to A-3) classical dune-backed coastlines as or dune-backed coastlines.

there are hardened, engineered structures between the open coast and powerblock, and sometimes no traditional dune present at the site. In these situations, what is the staffs recommendations regarding SLR and erosional effects? Or even how to estimate erosional effects in general?

13. A-3. Non- The report discusses climate change and If the NRC staff is expecting stationarity: Climate provides some details with respect to consistent treatment of climate Variability, Climate SLR. However, there is a general change impacts, the NRC staff should Change, and Sea discussion where it is noted that current provide a discussion based on current Level Rise (Page A-2 difficulty [exists] in translating knowledge, on which of the external to A-3) climate research findings into practical flood hazards would be significantly applications for hydrologic design impacted by climate change and how problems. In spite of the difficulties, climate change extrapolations should decisions need to be made, and several be treated.

State and Federal agencies have developed frameworks for assessing climate change risks for water resource applications.

While a number of references are identified for specific locations, little guidance is provided in that section identifying expectations as to which approaches may be preferred (or acceptable) and which hazards other than storm surge should be evaluated.

14. E-3. Source of The document suggests use of synthetic Elaborate on the use of synthetic Historical Storm storms to account for conditions more storm sets and how those sets should severe than those in the historical record be developed to properly address the but considered to be physically 4

Section Comment/Basis Recommendation Information (Page reasonable. Could the staff provide staffs concern about lack of historical E-3) guidance on when and how synthetic storm records.

storms should be developed?

Presumably, synthetic storm sets are most applicable where the historical record of extreme tropical cyclone events are relatively lacking, such as the northeast U.S. coast, but confirmation of where this technique should be applied and what type of meteorological analysis would be deemed acceptable as physically reasonable storm parameters would help guide future evaluations.

15. E-4.2 Coupled Wind, Acceptable hydraulic modeling software, Include Delft3D (and other Wave, and notably Delft3D, should be included by acceptable, state-of-the-art software Hydrodynamic reference for determine the storm surge options) by reference.

Modeling (Page E-4 and wave parameters for a PMH event.

to E-5)

16. F-1. Discussion The seiche methodology acknowledges Address the credible forcing (Pages F-1 to F-2) that if the natural oscillation mode(s) of a questions and update Section F.1 as water body are not dissimilar from needed based on those responses.

credible forcing presumably from meteorological events, such as multiple squall lines/derechos occurring on the water body at that natural resonance frequency, would there be other expected meteorological or non-meteorological forcing to be included in the analysis? Presumably, the geometry/direction of expected squall lines would be included in the credible forcing evaluation. For example, squall lines may only occur in an east-west direction, so they would not need to be considered in a north-south direction.

17. G-3. Tsunami Multiple modeling software options are Include Delft3D by reference as an Computational noted, but other commercial hydraulic acceptable shallow-water wave Modeling Tools software, namely Delft3D is comparable propagation solver for tsunami (Page G-3 to G-4) to ADCIRC in solving shallow-water wave applications.

propagation and should be included by reference as an appropriate technique.

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Section Comment/Basis Recommendation

18. J-1. Coincident Outside of a screening-type application Include further methods for assessing Wave Height and J- for the hazard, significant wave height, wave overtopping and wave forces

2. Wave Runup maximum wave height, and wave runup which are more critical to plant safety (Page J-1 to J-2) are relatively inconsequential parameters. than wave height or wave runup It would be rare that the largest storm height alone.

waves break at/onto powerblock structures directly as larger waves would break over shallow embankments/other site features. Hydrodynamic/hydrostatic forces from the breaking/broken waves and overtopping volumetric rates around the power block area are of critical concern, but a further explanation of an acceptable framework outside of the brief mention of ACES/CEDAS and the USACE CEM. These effects are the critical component to assess the adequacy of protection measures, so more details about what the staff would deem an acceptable method would be welcomed.

19. J-5. Water borne The discussion in this section seems Expand discussion and perhaps debris relatively brief. Expand the discussion to include an example application and more clearly indicate the expectations for provide relevant references of treating this phenomenon. reasonable examples of an assessment of the impact of water borne debris.

20. J-6. Effects of The USACE CEM is referenced for Elaborate on erosional/depositional Sediment Erosion or consideration of erosional/depositional effects analyses expected by the Deposition (Page J- effects for structures (e.g., embankment staff.

3) walls, roads). Outside of standard scour methodology, does the staff expect any other analysis to assess the adequacy of plant design and protection measures with respect to erosional/depositional effects?

21. J-6. Effects of Appendix G (Flooding Caused by Comment on the applicability of the Sediment Erosion or Tsunami) references Appendix J for USACE CEM scour and Deposition (Page J- related effects analyses. Is the USACE erosional/depositional effect methods

3) CEM an adequate framework for are for tsunami waves.

assessing sedimentation/depositional effects from tsunami events? Tsunami waves are long period and behave 6

Section Comment/Basis Recommendation differently than swell/storm wind waves to which the scour and other similar equations presented in the USACE CEM have been calibrated. Have those equations been calibrated for tsunami-like events?

22. J-6. Effects of The guidance is unclear in how this Expand upon what specific issues are Sediment Erosion or evaluation is expected to be performed, expected to be addressed within the Deposition (Page J- and in particular its role in a hazard deposition/erosion challenge within

3) assessment as opposed to fragility the assessment of SSC fragility.

assessment. In evaluating the scenario Consider including an example in the impacts of erosion for assessments of RG as to what might be reasonable to SSCs, is the concern about the short- include in the treatment of these term impact of this mechanism on SSCs phenomena.

(single storm/weather/flood impacts) or the combined impact of the erosion /

deposition challenge over a number of months/years due to repeated events.

Earlier versions of this RG didnt address this issue.

23. Appendix K-1 There is paragraph in this section that Every design will have unique states it recognizes some advanced elements that may increase or reactor designs may use materials that decrease susceptibility to flooding, be have potential for adverse reactions. It it composition of coolant, reliance on specifically calls out sodium fast reactors electrical power, etc. It is unclear for their use of sodium as a coolant. why sodium is explicitly stated here, However, every design will have unique rather than a broad recognition that elements that may or may not contribute designs should consider to flooding susceptibility. susceptibilities to flooding holistically.

24. Appendix K-2, The flow chart starts with Describe Site Recommend initially identifying if Figure K-1 Characteristics. Some advanced nuclear flooding is a safety challenge to the power plant designs can demonstrate plant design.

that there will be no radiological release no matter the size of the flood. Thus, no site flood characteristics are necessary to demonstrate safety.

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