ML23209A769

Draft Audit Results File TSTF-505 and 50.69 (E-mail Dated 6/14/2023) (EPIDs L-2022-LLA-0185 and L-2022-LLA-0186)

ML23209A769
Person / Time
Site:	Nine Mile Point
Issue date:	06/14/2023
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Reynolds R Constellation Energy Generation
References
EPID L-2022-LLA-0185, EPID L-2022-LLA-0186
Download: ML23209A769 (1)

Text

From: Richard Guzman To: Reynolds, Ronnie J:(Constellation Nuclear)

Subject:

Draft Audit Results File Date: Wednesday, June 14, 2023 1:00:00 PM Attachments: NMP1 - Preliminary Audit Results (June 14 2023) DRAFT.pdf

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Rich Guzman Sr. PM, Division Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Office: O-9C7 l Phone: (301) 415-1030 Richard.Guzman@nrc.gov

June 14, 2023 Preliminary Audit Results for Nine Mile Point, Unit 1, to Adopt TSTF-505 and 50.69 Information Needed on Docket (Potential RAIs)

Audit Questions CLOSED Question Staff Observations (including any Refinements to Questions) (response not needed on docket) 01 (TS LCOs 3.6.3.b and The table correction needs to be docketed. The whole table does not 05 (N1-OP-19, Circ Water, 50.69) 3.6.3.e.2, TSTF-505) need to be resubmit, just a description of the change is fine.

02 (TS LCOs 3.6.2i, TSTF-505) - 07 (Gap assessment, TSTF-505) 03 (TS Markups, TSTF-505) - 08 (F&O 1-2 disposition, TSTF-505) 04 (License Cond, TSTF-505) - 15 (Open phase cond., TSTF-505) 06 (FLEX credit, TSTF-505) Part (6.b): Regarding operating trailers at low speeds, provide further 23 (Gap assessment, 50.69) justification that ensure low speed operations during an event (heighten stress levels).

Regarding the screening of battery depletion pre-initiator, provide further screening justification, such as currently FLEX PRA modeling Regarding the modeling of declaring an ELAP, provide clarification on the modeling of the cognitive operator action and its impact on crediting FLEX strategies in the PRA model.

Part (6.c): Additional information needed in response (see Note 1) 22 (FLEX credit, 50.69) Part (22.c): Question was revised (see Note 2) 24 (F&O 1-2 disposition, 50.69) 09 (Small leak surrogate, Add to response the meaning of small containment leak and that it is TSTF-505) associated with the LERF risk metric.

10 (MRule, TSTF-505) -

11 (Shared systems, TSTF-505) -

12 (Digital I&C, TSTF-505) If the loss of feedwater initiating event is modeled separately, then include in the response a discussion on sensitivity of the RICTs to loss of feedwater initiating event frequency.

13 (Seasonal variations, -

TSTF-505) 14 (Unscheduled PRA -

updates, TSTF-505) 16 (High winds penalty in RICT -

estimates, TSTF-505) 17 (SSC design wind capacity, Additional information needed in response (see Note 3)

TSTF-505) 18 (Design wind speed capacity Additional information needed in response (see Note 4) parameter and fragility calcs, TSTF-505) 19 (Main Stack contribution to High The licensees response that the stack would have a vertically Wind, TSTF-505) dominated collapse appears to call into question the assumption that the collapse would have a 31% chance of falling on a critical structure (on the basis of the fact that the critical structures comprise of 31% of the spatial area). A vertically dominated collapse could distribute multiple fragments of the stack debris over a wider area.

The licensee should provide a reasonably conservative or bounding evaluation of the probability of the debris impacting the critical structures given the composition of the stack materials, weight, size, etc, and the assumption that stack structure would experience a vertically dominated collapse.

20 (Tornado Missile Vulnerability, -

TSTF-505) 21 (High Wind Risk for Maint. If any of the calculations change (e.g., questions 17, 18, 19) based on Config, TSTF-505) staff questions, then the calculations pertaining to Question 21 would need to be updated.

25 (Overall Use of NEI 00-04 -

Figure 5-6, 50.69) 26 (HWSSEL, 50.69) -

27 (Local Intense Precipitation, -

50.69) 28 (Screening of Snowfall Risk, -

50.69)

Note 1: Add to response a discussion on whether the RICTs for plant configurations involving more than one LCO entry are significantly impacted by FLEX uncertainties (e.g., expand the sensitivity study to include multiple LCO entries whose RICT is sensitive to FLEX uncertainties and less than the 30 day backstop). Also, discuss the basis for the chosen plant configurations involving more than one LCO entry.

Note 2: [Question Revised] Provide an updated assessment of the impact on 50.69 SSC categorization by FLEX equipment credited in NMP1s PRA models. This assessment should include, if required, any modifications to FLEX modeling based on the issues raised in this question.

Include in this discussion, the impact of FLEX on exceeding importance rankings for affected SSCs and whether the uncertainty associated with FLEX modeling is a key source of uncertainty for 50.69. If this uncertainty is key, then describe and provide a basis for how this uncertainty will be addressed for 50.69 categorization.

Two examples of sensitivity studies:

- ML20303A307 (APLA RAI 05, Tables APLA-05-A.2 and APLA-05-A.3)

- ML20177A535 (APLA RAI 03: Tables B-1 and B-2)

Note 3: Response needs additional information:

• Need supporting justification for the DG board room capacity of 175 mph for walls and roof.

• Remove response in second paragraph of part (b) (i.e., In addition for more details).

Note 4: Response needs additional information:

(a) Provide calculation method that was used for converting fastest-mile wind speed to 3-second gust wind speed.

(b) Need to define new nomenclature for the Vd 3-second gust wind speed.

(c) Provide further justification for using Screenhouse wind speed of 150 mph instead of the current 125 mph.

(d) The licensee may change their current method for calculating Vm for the Screenhouse to be consistent with the other SSCs. Within the next few weeks, the licensee should update the NRC staff of which method will be used to calculate the Screenhouse Vm.

(e) Uncertainty factor (c) should be associated with the Vm calculation. Whichever value is selected, justify that it is conservative and bounding.

(f) Part (f) is only needed if the Uncertainty factor (c) cannot be justified to be conservative and bounding. If Question 18 is stated in an RAI, the NRC staff will modify part (f) accordingly.

(g) Update response per answers (c) through (f)