ML23205A241

NRC Staff Follow-up Comments on Audit Questions 6a, 6b, and 6c TSTF-505 and 50.69 Regulatory Audit (E-mail Dated 7/11/2023) (EPIDs L-2022-LLA-0185 and L-2022-LLA-0186)

ML23205A241
Person / Time
Site:	Nine Mile Point
Issue date:	07/11/2023
From:	Richard Guzman NRC/NRR/DORL/LPL1
To:	Rossi M Constellation Energy Generation, Constellation Nuclear
References
EPID L-2022-LLA-0185, EPID L-2022-LLA-0186
Download: ML23205A241 (1)

Text

From: Richard Guzman To: Rossi, Matthew:(Constellation Nuclear)

Cc: Reynolds, Ronnie J:(Constellation Nuclear); Passehl, David Bcc: Richard Guzman

Subject:

RE: NMP1 Revised Responses for Audit Questions 17 and 19 Date: Tuesday, July 11, 2023 9:33:00 AM

Matt,

Below are comments from the NRC staff on the revised responses to NMP1 TSTF-505 audit questions 6a, 6b and 6c. Please include as appropriate when completing the updated response to be docketed.

Comment on revised response to audit question 6.a:

In Table 6a-1 for portable generator failure to run after 1st hour, the base case was shown in the table as 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> instead of 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />. The product of 6.16E-2 is correct for 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />.

Comments on revised response to audit question 6.b:

Information from both the original response to 6.b and the revised response to 6.b are needed on the docket.

Revised response to audit question 6.b states, 15 mph = 2,200 FT/min. Should that be 25 mph? Please correct this in revised response.

The revised response states, any incentive for excessive speed is considered negligible risk. Given the response lists 25 mph, is this the highest speed that can be expected? Please clarify in revised response.

Regarding the HEP for jump starting a depleted FLEX DG battery using the tow vehicle. Are the battery voltages compatible, i.e., 12V vs. 24V (please explain)?

If not, explain how the tow vehicle battery would be utilized to start the FLEX DG.

Comments on revised response to audit question 6.c:

In Table 6c-1 for portable generator failure to run after 1st hour, the base case was shown in the table as 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> instead of 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />. The product of 6.16E-2 is correct for 23 hours2.662037e-4 days <br />0.00639 hours <br />3.80291e-5 weeks <br />8.7515e-6 months <br />.

For the sensitivity study in Table 6c-2, what is the RICT sensitivity results for LCO combination 3.6.3.H (one DC electrical power subsystem inoperable) and 3.6.3.C, and discuss the results?

The revised response concluded that the RICT is not sensitive to the uncertainties associated with FLEX equipment failure probabilities, and based on the results of the sensitivity study, no specific global risk management actions (RMAs) were identified related to these uncertainties.

However, the NRC staff notes that the sensitivity study results in Table 6c-2 show significant decreases in RICT (20 percent) for LCO combination 3.6.3.C and 3.1.3.B (one EDG /offsite & one EC train). Also, for single LCO 3.6.3.H (one DC train), the decrease in RICT (10.4 percent) can be considered significant.

Therefore, the basis for the licensees conclusion regarding this sensitivity study (i.e., the impact is still assessed to be minor) is unclear. The impact of FLEX failure probability uncertainties appears to significantly impact RICT calculations for certain LCOs and that this is a key source of uncertainty.

Considering these observations,

a. Describe and provide a basis for how the uncertainty of FLEX equipment failure probabilities will be addressed in the RMTS program (e.g.,

programmatic changes such as identification of additional RMAs, program restrictions, or the use of bounding analyses which address the impact of the uncertainty). If the programmatic changes include identification of additional RMAs, then (1) describe how these RMAs will be identified prior to the implementation of the RMTS program, consistent with the guidance in Section 2.3.4 of NEI 06-09-A; and (2) provide RMA examples that may be considered during a RICT program entry to minimize any potential adverse impact from this uncertainty and explain how these RMAs are expected to reduce the risk associated with this uncertainty.

-OR-

b. Provide a mechanism (e.g., a license condition/implementation item) to incorporate NRC-accepted FLEX parameter data in the NMP1 PRA models used for RICT calculations prior to implementing the RICT program.