ML22048C223

Audit Agenda and Questions for License Amendment Request to Adopt TSTF-505, Risk-Informed Extended Completion Times - RITSTF Initiative 4B

ML22048C223
Person / Time
Site:	Hatch
Issue date:	03/01/2022
From:	John Lamb Plant Licensing Branch II
To:	Gayheart C Southern Nuclear Operating Co
Lamb J
References
EPID L-2021-LLA-0199
Download: ML22048C223 (23)

Text

March 1, 2022 Ms. Cheryl A. Gayheart Regulatory Affairs Director Southern Nuclear Operating Co., Inc.

3535 Colonnade Parkway Birmingham, AL 35243

SUBJECT:

EDWIN I. HATCH NUCLEAR PLANT, UNITS 1 AND 2 - AUDIT AGENDA AND QUESTIONS FOR LICENSE AMENDMENT REQUEST TO ADOPT TSTF-505, RISK-INFORMED EXTENDED COMPLETION TIMES - RITSTF INITIATIVE 4B (EPID L-2021-LLA-0199)

Dear Ms. Gayheart:

By letter dated October 26, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21300A153), Southern Nuclear Operating Company (SNC, the licensee) submitted a license amendment request (LAR) for Edwin I. Hatch Nuclear Plant (Hatch), Units 1 and 2. The proposed LAR would modify the plants Technical Specification requirements to permit the use of risk-informed completion times in accordance with Technical Specification Task Force Traveler TSTF 505, Provide Risk-informed Extended Completion Times, RITSTF [Risk-Informed Technical Specification Task Force] Initiative 4b.

On November 29, 2021 (ADAMS Accession No. ML21309A000), the U.S. Nuclear Regulatory Commission (NRC) staff issued an audit plan that conveyed intent to conduct a regulatory audit to support its review of the subject license amendment. In the audit plan the NRC staff requested an electronic portal setup and provided a list of documents to be added to the portal.

The NRC staff has performed an initial review of these documents and developed a list of audit questions. The proposed date for the audit is from Tuesday, April 5, 2022, through Thursday, April 7, 2022. The proposed agenda for the audit is provided as Enclosure 1, and the list of Audit questions are provided as Enclosure 2 to this letter.

If you have any questions, please contact me at (301) 415-3100 or by e-mail at John.Lamb@nrc.gov.

Sincerely,

/RA/

John G. Lamb, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-321 and 50-366

Enclosures:

1. Audit Agenda

2. Audit Questions cc: Listserv

AUDIT AGENDA - HATCH TSTF-505 LAR Day 1 - Tuesday, April 5, 2022 9:00 a.m. to 12:00 p.m. Eastern Time (ET)

Entrance Meeting o Opening comments by U.S. Nuclear Regulatory Commission (NRC) and Southern Nuclear Operating Company (SNC, the licensee) o Introductions and logistics Electrical power distribution presentation, Real-time risk (RTR) model demonstration, and risk-informed completion times (RICT) sample calculations by SNC Discuss RTR model and calculation of RICT estimates o Dialog item - RTR model benchmarking, update, and interim evaluation process.

o Impact of seasonal variations (Question (Q) Number 1 (Q1) - Probabilistic Risk Assessment (PRA) Licensing Branch-A (APLA))

o Consideration of shared systems in RICT calculations (Q2 - APLA) 1:00 p.m. to 4:00 p.m. ET Discuss uncertainty analysis process and disposition of assumptions (Q3 and 4 - APLA)

Open phase condition (Q5 - APLA)

Digital instrumentation and control modeling (Q6 - APLA)

In-scope LCOs and corresponding probabilistic risk assessment (PRA) modeling (Q7 -

APLA)

Summary of the day (3:30 p.m.)1 Day 2 - Wednesday, April 6, 2022 9:00 a.m. to 12:00 p.m. ET Summary of previous day and review open items Discussion of technical specification questions (Q14 thru 23 - Technical Specification Branch (STSB))

Dialog item - RICT program administrative controls (TS 5.5.16) 1:00 p.m. to 4:00 p.m. ET Seismic and tornado missile (Q10 thru 13 - PRA Plant Licensing Branch-C (APLC))

Fire PRA uncertainty associated with methods (Q8 - PRA Plant Licensing Branch-B (APLB)) 2 National Fire Protection Association (NFPA) 805 committed modifications and implementation items (Q9 - APLB) 2 Summary of the day (3:30 p.m.)1 1 If discussion topics are completed early, additional discussions for Day 1 may be on the next days agenda items.

2 If the afternoon session runs long the remaining questions will be covered during the afternoon of Day 3 Day 3 - Thursday, April 7, 2022 9:00 a.m. to 12:00 p.m. ET Summary of previous day and review open items Discuss Electrical Engineering Branch (EEEB) audit questions (Q24 thru 29) 1:00 p.m. to 4:00 p.m. ET Follow up on any remaining or new open action items Technical summary meeting with SNCs audit team (3:00 p.m.)

Formal exit meeting (4:00 p.m.)

ENCLOSURE 2 AUDIT QUESTIONS LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATIONS TO ADOPT TSTF-505, REVISION 2 SOUTHERN NUCLEAR OPERATING COMPANY EDWIN I. HATCH NUCELAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-321 AND 50-366 By application dated October 26, 2021, (Agencywide Documents Access and Management System (ADAMS) Accession No.ML21300A153) Southern Nuclear Operating Company (SNC) submitted a license amendment request (LAR) for Edwin I. Hatch Nuclear Plant (Hatch), Units 1 and 2.

The amendment would revise technical specification (TS) requirements to permit the use of risk-informed completion times (RICTs) for actions to be taken when limiting conditions for operation (LCOs) are not met. The proposed changes are based on Technical Specifications Task Force (TSTF) Traveler TSTF-505, Revision2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative4b, dated July 2, 2018 (ADAMS Accession No. ML18183A493). The U.S. Nuclear Regulatory Commission (NRC) issued a final model safety evaluation (SE) approving TSTF 505, Revision 2, on November 21, 2018 (ADAMS Accession No. ML18269A041).

The NRC staff determined that the following information is needed to complete its review.

Probabilistic Risk Assessment Licensing Branch A (APLA) Audit Questions QUESTION 1 (APLA) - Impact of Seasonal Variations The Tier 3 requirement of Regulatory Guide (RG) 1.177, Rev. 2, An Approach for Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications, January 2021 (ADAMS Accession No. ML20164A034), stipulates that a licensee should develop a program that ensures that the risk impact of out of service equipment is appropriately evaluated prior to performing any maintenance activity. Nuclear Energy Institute (NEI) 06-09, Rev. 0, Risk Informed Technical Specifications Initiative 4b: Risk Managed Technical Specifications (RMTS)

(ADAMS Accession No. ML063390638), and the NRCs SE to this guidance state that for the impact of seasonal changes either conservative assumptions should be made or, the probabilistic risk assessment (PRA) should be adjusted appropriately to reflect the current (e.g.,

seasonal or time of cycle) configuration.

Table E4-4 of the LAR dated October 26, 2021, states for both low and high abnormal ambient temperatures that Hatchs Heating, Ventilation, and Air-Conditioning (HVAC) systems are designed to operate between outside temperatures between 20 degrees Fahrenheit (°F) and 95°F. It further states that it is assumed that exceedance of these temperatures would be minimal, and the thermal inertia of the concrete structures is relied upon for safety-related equipment functionality. The NRC staff notes that LAR Enclosure 8, dated October 26, 2021, does not appear to address when and how PRA adjustments are made to seasonal variations due to changes in temperature-related design requirements. Therefore, address the following:

a) Discuss the modeling that will be subject to adjustment due to seasonal variations such as hot or cold weather or other environmental factors (e.g., water levels) that can impact the performance of plant systems. Explain what kind of adjustments will be made and clarify whether they will be made conservatively like the adjustments that will be made for HVAC dependency b) Explain what criteria (e.g., trigger) are used to know when PRA adjustments due to seasonal variations need to be made in the real-time risk (RTR) and justify that this approach is consistent with the guidance in NEI 06-09.

QUESTION 2 (APLA) - Consideration of Shared Systems in Risk Informed Completion Time (RICT) Calculations Regulatory Guide (RG) 1.200, Revision 2, An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities, March 2009 (ADAMS Accession No. ML090410014), states that The base PRA serves as the foundational representation of the as-built, as-operated, and maintained plant necessary to support an application.

The LAR, Enclosure 12, dated October 26, 2021, indicates the existence of cross-ties between units. Please clarify what systems are shared, how they are shared, whether they are capable of supporting both units in an accident, and how the shared systems are credited for each unit in the PRA models. The NRC staff notes that for certain events, such as dual unit events (e.g., loss of offsite power) credit for a system may be limited to one unit. Therefore, address the following:

a) Explain how shared systems credited in the RTR model that support the RICT calculations are modelled for each unit in a dual unit event.

b) If the impact of events that can create a concurrent demand for the system shared by both units and credited in the RTR model is not addressed, then justify that this modelling exclusion has an inconsequential impact on the RICT calculations.

QUESTION 3 (APLA) - PRA Model Uncertainty Analysis Process The NRC staffs SE to NEI 06-09 specifies that the LAR should identify key assumptions and sources of uncertainty and to assess and disposition each as to their impact on the RMTS application. NUREG-1855, Revision 1, Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decision Making, Main Report, dated March 2017 (ADAMS Accession No. ML17062A466) presents guidance on the process of identifying, characterizing, and qualitative screening of model uncertainties.

Section 2 of the LAR, Enclosure 9, dated October 26, 2021, states that the screening of sources of uncertainty was conducted in accordance with Step E-1 and E-2 of NUREG-1855. Please clarify if only the consensus modeling screening of E-1.4 was utilized for the Hatch TSTF-505 uncertainty analysis. The LAR continues by stating that the remaining sources of uncertainty (after the NUREG-1855 screening) were subjected to sensitivity analysis to determine their impact on this application with the results provided in the LAR Enclosure. The NRC staff notes that only one unscreened source of uncertainty was provided in Table E9-1 for internal events and internal flooding PRA hazard models. Please explain how the Hatch uncertainty process only identified one source of uncertainty that required a sensitivity study. Therefore, address the following:

a) Describe the general evaluation criteria used to consistently screen sources of uncertainties from an initial comprehensive list of assumptions and sources of PRA modeling uncertainty (including those associated with plant specific features, modeling choices, and generic industry concerns), to produce the list of candidate key assumptions and sources of uncertainty that is presented in the LAR.

b) Discuss the criteria used to consistently determine when a sensitivity study was needed to address the identified source of uncertainty.

QUESTION 4 (APLA) - Dispositions Assumptions and Sources of Uncertainty The NRC staffs SE for NEI 06-09 specifies that the LAR should identify key assumptions and sources of uncertainty and to assess and disposition each as to their impact on the RMTS application. NUREG-1855, Revision 1, presents guidance on the process of identifying, characterizing, and qualitative screening of model uncertainties.

a) Enclosure 9 to the LAR dated October 26, 2021, provides dispositions for candidate key assumptions and sources of uncertainty in Table E9-1 for this application. The entry, regarding minimum joint human error probability (JHEP) states that a sensitivity study was performed for a select sample of TS that are included in the RICT program. The NRC staff notes that operator actions can impact each PRA hazard model across a wide spectrum of scenarios and mitigating equipment. Please ndicate the criteria used to determine which TS RICTs to be sampled and which TS limiting conditions of operation (LCO) were selected. Therefore, address the following:

i.

Provide the criteria used to determine which TS LCOs should be included in the sensitivity studies to determine the source of uncertainty impact on RICT calculations.

ii. Provide the list of TS LCOs selected for the minimum JHEP sensitivity study.

iii. Provide justification that the TS LCOs selected in Part (b) are the most impacted RICTs for this source of uncertainty.

b) The LAR, Enclosure 9, Table E9-3, Task #3, Cable Selection, explains that some components were assumed conservatively to be failed based on lack of cable data. Such components were referred to as Unknown Location (UNL) components. The LAR states that a sensitivity analysis was performed to determine the impact of the treatment of UNL components by removing all UNL components from every fire scenario. Based on the results of the sensitivity study, the LAR states that this issue does not introduce significant conservatismsthat mask key risk insights. The LAR does not provide the results of the uncertainty analyses nor does it address the impacts to applicable RICTs. The NRC staff reviewed the sensitivity study results provided in the fire PRA uncertainty and sensitivity analysis report on the portal and notes that the impact to core damage frequency (CDF) and large early release frequency (LERF) is not insignificant (i.e., risk reduction in the 36 to 50 percent range) and that the impact for the RICT program was not performed. The NRC staff also notes that conservatism in PRA modeling could have a nonconservative impact on the RICT calculations while having only a small or modest impact on total CDF or LERF.

Please clarify if that the modelling assumption applied to untraced cables and to functions/systems for which circuits analysis was not performed has no impact on the RICT program calculations. If a structure, system, and component (SSC) is part of a system not credited in the fire PRA or it is supported by a system that is assumed to always fail, then the risk-increase due to taking that SSC out of service is masked. Therefore, address the following:

i.

Identify the UNL systems or components that are assumed to be always failed in the PRA or are not included in the PRA.

ii. Justify that this assumption has an inconsequential impact on the RICT calculations by describing and performing a sensitivity study using LCO conditions that could be most impacted by this modeling uncertainty having RICTs less than the 30-day backstop.

iii. As an alternative to part (b) above, identify the LCO conditions impacted by the treatment of this modelling uncertainty for which risk management actions (RMAs) will be applied during a RICT. Include discussion of the kinds of RMAs that would be applied and justification that the RMAs will be sufficient to address the modeling uncertainty.

QUESTION 5 (APLA) - Open Phase Condition By letter dated September 20, 2021 (ADAMS Accession No. ML21253A113), the NRC staff closed out Bulletin (BL) 2012-01, Design Vulnerability in Electric Power System, deterministically.

The NRC issued BL 2012-01 on July 27, 2012 (ADAMS Accession No. ML12074A115). As part of the initial Voluntary Industry Initiative (VII) for mitigation of the potential for the occurrence of an open phase condition (OPC) in electrical switchyards, some licensees have installed plant modifications (e.g., Open Phase Isolation System (OPIS)). The NEI 19-02, Guidance for Assessing Open Phase Condition Implementation Using Risk Insights, dated June 20, 2019 (ADAMS Accession No. ML19172A086, discusses performing estimations of OPC and OPIS risk, and further states that the risk impact of an OPC can vary widely dependent on electrical switchyard configuration and design. Furthermore, Section 2.3.4 of NEI 06-09 specifies that criteria shall exist in PRA configuration risk management to require PRA model updates concurrent with implementation of facility changes that significantly impact RICT calculations.

Considering these observations, provide the following information:

a. For Hatch, discuss the evaluation of the risk impact associated with OPC events including the likelihood of OPC-initiated plant trips and the impact of those trips on PRA modeled SSCs and indicate the extent to which the Hatch Bulletin response addressed this issue.

b. Confirm whether any installed equipment and associated operator actions are credited in the PRAs to address OPC. If equipment and associated operator actions are credited, then provide the following information:

i.

Describe the equipment and associated actions that are credited in the PRA models.

ii.

Describe the impact that this treatment, if any, has on key assumptions and sources of uncertainty.

iii.

Discuss human reliability analysis (HRA) methods and assumptions used for crediting alarm manual response.

iv.

Discuss how OPC-related scenarios are modeled for non-internal event scenarios such as internal floods, fire, and seismic.

v.

Regarding inadvertent actuation of the open phase detection system open phase isolation:

1. Explain whether scenarios regarding inadvertent actuation of the OPIS, if applicable, are included in the PRA models that support the RICT calculations or RISC.

2. If inadvertent OPIS actuation scenarios are not included in the PRA models, then provide justification that the exclusion of this inadvertent actuation does not impact the RICT calculations or risk-informed safety class (RISC) categorizations.

c. If OPC and the open phase detection system and ability to manually mitigate an open phase condition are not included in the application PRA models, then provide justification that the exclusion of this failure mode and mitigating system does not impact the RICT program.

d. As an alternative to Part (c), propose a mechanism to ensure that OPC-related scenarios are incorporated into the PRA models prior to implementing the RICT program.

QUESTION 6 (APLA) - Digital Instrumentation and Control Modeling NEI 06-09 states concerning the quality of the PRA model that RG 1.174, Revision 1, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis, November 2002 (ADAMS Accession No. ML023240437), and RG 1.200, Revision 1, An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities, January 2007 (ADAMS Accession No. ML070240001), define the quality of the PRA in terms of its scope, level of detail, and technical adequacy. The quality must be compatible with the safety implications of the proposed TS change and the role the PRA plays in justifying the change.

Regarding digital instrumentation and control (I&C), the NRC staff notes the lack of consensus industry guidance for modeling these systems in plant PRAs to be used to support risk-informed applications. In addition, known modeling challenges exist, such as the lack of industry data for digital I&C components, the difference between digital and analog system failure modes, and the complexities associated with modeling software failures including common-cause software failures. Also, though reliability data from vendor tests may be available, this source of data is not a substitute for in-the-field operational data. Given these challenges, the uncertainty associated with modeling a digital I&C system could impact the RICT program. Please indicatewhether the licensee credited digital I&C systems in the PRA models that will be used in the RICT program or whether this modelling can impact the RICT calculations. Therefore, address the following:

a) Clarify whether digital I&C systems are credited in the PRA models that will be used in the RICT program.

b) If digital I&C systems are credited in the PRA models that will be used in the RICT program, provide justification that demonstrates the modeling uncertainty associated with crediting digital I&C systems has an no adverse impact on the RICT calculations.

QUESTION 7 (APLA) - In-Scope LCOs and Corresponding PRA Modeling The NRCs SE to NEI 06-09 specifies that the LAR should provide a comparison of the TS functions to the PRA modeled functions to show that the PRA modelling is consistent with the licensing basis assumptions or to provide a basis for when there is a difference. LAR, Table E1-1 identifies each TS LCO proposed for the RICT program, describes whether the systems and components participating in the TS LCO are implicitly or explicitly modeled in the PRA, and compares the design basis and PRA success criteria. For certain TS LCO Conditions, the table explains that the associated SSCs are not modelled in the PRAs but will be represented using a surrogate event that fails the function performed by the SSC.

For some LCO conditions, the LAR did not provide enough description for the NRC staff to conclude that the PRA modeling will be sufficient for each proposed LCO Condition. Address the following:

a) Regarding TS 3.3.5.1.B, Table E1-1 states that the drywell high pressure instruments have placeholders for fire impacts that can be used as surrogate events. Please indicate when the surrogates would be used, if the surrogates are adequately bounding, and that the fire impacts are appropriate surrogates for the internal events (including internal flooding) model.

i.

Describe when the drywell high pressure instrument fire impacts would be used as surrogates in RICT calculations.

ii. Provide justification that the fire impact surrogates appropriately bound the loss of function associated with the out-of-service component.

iii. Describe and justify how fire impact surrogates represent the out-of-service component in the internal events (including internal flooding) PRA models for RICT calculations.

b) Regarding TS 3.3.5.1.E, Table E1-1 states that the minimum flow failing to close function is not included in the model due to restricting orifice downstream of valve limiting flow.

Please explain if a surrogate is being proposed for the close function.

Explain how the minimum flow failing to close function is addressed in the RTR model to support RICT calculations (i.e., implicit or explicit).

c) Regarding TS 3.6.1.2.C, Table E1-1 states that early containment isolation failure will be used as a surrogate when one of the primary containment airlocks is inoperable. Please indicate the impact of this surrogate on large early release calculations compared to the airlock.

i.

Briefly describe the overall impact (i.e., plant response) for the failure of early containment isolation on LERF.

ii. Provide justification that the impact described in Part (i) adequately bounds the inoperability of a containment airlock door.

d) Regarding TS 3.3.6.1.A, Table E1-1 states that since the functions are not modeled composite events will be used as surrogates. The LAR does not provide sufficient information to conclude why the surrogates are considered bounding.

Identify the specific events that are modeled as surrogates and why these events are bounding for use in the RICT.

e) Regarding TS 3.6.1.3.A, Table E1-1 states that, for the valves not modeled, a generic isolation failure event will be used as a surrogate. The LAR does not provide sufficient modeling information regarding the generic isolation failure event to conclude that the surrogates are bounding.

Identify the specific basic events that are modeled as surrogates and why these events are bounding for use in the RICT.

Probabilistic Risk Assessment Licensing Branch B (APLB) Audit Questions The NRC staff evaluates the acceptability of the PRA for each new risk-informed application and, as discussed in RG 1.174, recognizes that the technical acceptability of risk analyses necessary to support regulatory decisionmaking may vary with the relative weight given to the risk assessment element of the decision-making process. The NRC staff notes that the calculated results of the PRA are used to calculate an RICT, which subsequently determines how long SSCs (both individual SSCs and multiple, unrelated SSCs) controlled by TSs can remain inoperable. Therefore, the PRA results are given a very high weight in a TSTF-505 application, and the NRC staff requests additional information on the following issues that have been previously identified as potentially key FPRA assumptions.

QUESTION 8 (APLB) - Fire PRA Uncertainty Associated with Methods The LAR, Enclosure 9, Section 4 dated October 26, 2021, indicates that the Hatch fire PRA was developed using methods presented NUREG/CR-6850 and other more recent NUREGs, (e.g.,

NUREG-7150 and published frequently asked question FAQs) for fire PRA. Moreover, LAR presents the following from 5.5.16 of the TSs for the RICT program:

Methods to assess the risk from extending the Completion Times must be PRA methods used to support this license amendment, or other methods approved by the NRC for generic use; and any change in the PRA methods to assess risk that are outside these approval boundaries require prior NRC approval.

The NRC staff notes that since (or about the same time as) the Hatch NFPA 805 program NRC SE (ADAMS Accession No. ML20066F592) was issued June 11, 2020, further NRC endorsed guidance was issued that can impact the fire PRA modelling and potentially the RICT calculations. These fire PRA studies and methods include:

NUREG-2178, Volume 2, Refining and Characterizing Heat Release Rates from Electrical Enclosures During Fire (RACHELLE-FIRE) Volume 2: Fire Modeling Guidance for Electrical Cabinets, Electric Motors, Indoor Dry Transformers, and the Main Control Board, dated June 2020 (ADAMS Accession No. ML20168A655).

Therefore, for the above NRC-accepted fire PRA methods and studies, please address the following:

a) Explain whether the cited fire PRA guidance has been incorporated into the Hatch fire PRA and, as applicable, summarize the changes made to the fire PRA model. Indicate whether this change was PRA maintenance or a PRA upgrade as defined in American Society of Mechanical Engineers/American Nuclear Society (ASME/ANS) RA-Sa-2009, Section 1-5.4 and qualified by RG 1.200, Revision 3, December 2020 (ADAMS Accession No. ML20238B871), along with a justification for the determination. If this change constitutes a PRA upgrade, then discuss the focused-scope (or full-scope) peer review(s) that was performed to evaluate the change and provide any open Facts and Observations (F&Os) and associated dispositions from this peer review(s) in accordance with RG 1.200, Revision 3.

b) If the response to part (a) above indicates that the cited fire PRA guidance has not been incorporated into the Hatch fire PRA, then justify why application of the fire PRA guidance would have no adverse impact on the (1) TSTF-505 RICT calculations, and (2) estimated total CDF and total LERF. As part of this justification, identify any fire PRA methodologies used in the Hatch fire PRA that are no longer accepted by the NRC staff (e.g., guidance provided in Frequently Asked Question (FAQ) 08-0046, Closure of National Fire Protection Association 805 Frequently Asked Question 08-0046 Incipient Fire Detection Systems, ADAMS Accession No. ML093220426, has been retired by letter dated July 1, 2016, (ADAMS Accession No. ML16167A444). Provide technical justification for its use in the fire PRA supporting RICT calculations and evaluate the significance of its use on the risk estimates provided in Enclosure 5 of the LAR.

c) If in response to part (b) above, the cited fire PRA guidance has not been incorporated into the Hatch fire PRA and it cannot be justified that the application of the cited fire PRA guidance would have no adverse impact on the TSTF-505 RICT calculations, and estimated total CDF and total LERF, then propose a mechanism that ensures the cited fire PRA guidance (or other NRC acceptable methods) will be integrated into the Hatch fire PRA prior to implementation of the RICT program. If this fire PRA update is determined to be a PRA model upgrade per the ASME/ANS PRA standard, then include in this mechanism a process for conducting a focused-scope peer review and ensure any findings are closed by using an approved NRC process.

QUESTION 9 (APLB) - NFPA 805 Committed Modifications and Implementation Items Both RG 1.200, Revision 3 and NEI 06-09, state that the PRA models which support the risk-informed program must be maintained consistent with the as-built, as-operated plant. The Hatch NFPA 805 program NRC safety evaluation (SE) dated June 11, 2020 (ADAMS Accession No. ML20066F592) cites commitments made in Attachment S of the Hatch NFPA 805 LAR to perform plant modifications and complete implementation items (e.g., updated fire response procedures) before fully transitioning to the NFPA 805 program. These plant improvements were used to offset the risk increase associated with transitioning to the NFPA 805 program and show that the risk acceptance guidelines in RG 1.174, Revision 3 are met. Please indicate whether the NFPA 805 plant modifications and implementation items have been completed and if there exist any incomplete modifications or implementation items that can impact the RICT program. Therefore, address the following:

a) Confirm that the fire PRA model used to support the RICT program reflects the as-built, as-operated plant (e.g., do not credit NFPA 805 plant modifications or implementation items that are not yet complete).

b) If in response to part (a), it cannot be confirmed that the fire PRA models used to support the RICT program reflect the as-built, as-operated plant, then justify that the modeling credit for NFPA 805 plant modifications and/or implementation items not yet completed but credited in the fire PRA do not have an adverse impact on the RICT program.

Probabilistic Risk Assessment Licensing Branch C (APLC) Audit Questions QUESTION 10 (APLC) - Impacts of Seismic Hazard Spectral Frequencies Section 2.3.1, Item 7, of NEI 06-09, states that the impact of other external events risk shall be addressed in the RMTS program and explains that one method to do this is by performing a reasonable bounding analysis and applying it along with the internal events risk contribution in calculating the configuration risk and the associated RICT. The NRC staffs SE for NEI 06-09 states that Where PRA models are not available, conservative or bounding analyses may be performed to quantify the risk impact and support the calculation of the RICT.

In Section 5 of Enclosure 4 to the LAR, the licensee discussed the effect of using different seismic hazard curves with different spectral frequencies on the seismic penalty for use in the RICT calculations. The licensee provided a comparison of seismic core damage frequency (SCDF) values obtained from convolution of the hazard curves from the probabilistic seismic hazard analysis (PSHA) in the Hatch Seismic Hazard Reevaluation and Screening Report (2014; ADAMS Accession No. ML14092A017) and the plant-level fragility based on the high confidence of low probability of failure (HCLPF) from the Hatch Individual Plant Examination of External Events (IPEEE). Hazard curves for four different spectral frequencies (peak ground acceleration (PGA), 10 Hz, 5 Hz, and 2.5 Hz) and HCLPF values adjusted per the Hatch IPEEE seismic margins earthquake (SME) ground response spectra curve were used, and the comparison shows that the PGA-based SCDF is approximately 15-percent lower than those based on other spectral frequencies. The licensee also stated that, if the ground motion response spectra (GMRS) from the 2014 Hatch PSHA were used (instead of IPEEE SME spectra), the difference in the calculated SCDFs would be less than 10-percent.

a) Provide SCDF values for different spectral frequencies (PGA, 10 Hz, 5 Hz, and 2.5 Hz) obtained from calculations involving the GMRS from the 2014 HNP PSHA, demonstrating the difference in the calculated SCDFs is less than 10-percent.

b) Justify that the consideration of seismic hazard curves at frequencies other than the PGA does not significantly change the SCDF penalty proposed in the LAR.

QUESTION 11 (APLC) - Impact of Portable FLEX Equipment on Seismic Penalty The NRC memorandum dated May 30, 2017, Assessment of the Nuclear Energy Institute 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, Guidance for Risk-Informed Changes to Plants Licensing Basis (ADAMS Accession No. ML17031A269),

provides the NRCs staff assessment of challenges to incorporating FLEX equipment and strategies into a PRA model in support of risk-informed decision-making in accordance with the guidance of RG 1.200, Revision 2 (ADAMS Accession No. ML090410014).

With regards to equipment failure probability, in the May 30, 2017 memo, the NRC staff concludes (Conclusion 8):

The uncertainty associated with failure rates of portable equipment should be considered in the PRA models consistent with the ASME/ANS PRA Standard as endorsed by RG 1.200. Risk-informed applications should address whether and how these uncertainties are evaluated.

With regards to human reliability analysis (HRA), NEI 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, dated August 26, 2016 (ADAMS Accession No. ML16286A297), Section 7.5 recognizes that the current HRA methods do not translate directly to human actions required for implementing mitigating strategies. Sections 7.5.4 and 7.5.5 of NEI 16-06 describe such actions to which the current HRA methods cannot be directly applied, such as: debris removal, transportation of portable equipment, installation of equipment at a staging location, routing of cables and hoses; and those complex actions that require many steps over an extended period, multiple personnel and locations, evolving command and control, and extended time delays. In the memo dated May 30, 2017 (ADAMS Accession No. ML17031A269), the NRC staff concludes (Conclusion 11):

Until gaps in the human reliability analysis methodologies are addressed by improved industry guidance, [Human Error Probabilities] HEPs associated with actions for which the existing approaches are not explicitly applicable, such as actions described in Sections 7.5.4 and 7.5.5 of NEI 16-06, along with assumptions and assessments, should be submitted to NRC for review.

Section 2 of Enclosure 4 to the LAR states that, while Internal Events, Internal Flooding, and Fire PRA models credit only permanently installed FLEX equipment, portable FLEX equipment was credited in the Hatch Seismic PRA (SPRA) model. The Hatch SPRA is not directly used in the RICT program but used to provide selected input into the calculation of the SCDF and seismic large early release frequency (SLERF) seismic penalty. Please indicate how much impact of the portable FLEX equipment would have on the evaluation of the SCDF and SLERF penalty.

Provide a sensitivity study or other means that shows the impact of the portable FLEX equipment credited in the Hatch SPRA on the calculated SCDF and SLERF penalty values.

QUESTION 12 (APLC) - SCDF and SLERF Penalty Estimate Section 2.3.1, Item 7, of NEI 06-09 states that the impact of other external events risk shall be addressed in the risk management technical specification (RMTS) program and explains that one method to do this is by performing a reasonable bounding analysis and applying it along with the internal events risk contribution in calculating the configuration risk and the associated RICT. The NRC staffs SE for NEI 06-09 states that Where PRA models are not available, conservative or bounding analyses may be performed to quantify the risk impact and support the calculation of the RICT.

In the LAR, the seismic penalty approach is used to quantify the risk impact and to support the RICT evaluation. Section 5 of Enclosure 4 to the LAR indicates that a seismic PRA (SPRA) for the Hatch plant was developed and that the Hatch SPRA was not directly used in the RICT program but provided input into the calculation for SCDF and SLERF penalty values. The licensee compared the estimated SCDF penalty for the proposed RICT calculations against the point-estimate SCDF from the site-specific SPRA. In addition, the licensee used the SLERF to SCDF ratio from the site-specific SPRA to determine the SLERF penalty for use in the proposed RICT calculations.

The comparison of the estimated SCDF and SLERF penalties against the corresponding point-estimate mean values from the site-specific SPRA does not provide justification that the SCDF and SLERF penalty estimates are conservative. There is no upper bound on the change-in-risk calculation, and the change in risk can exceed the base SCDF and SLERF. However, it appears that the SPRA could provide the means to justify that the proposed SCDF and SLERF penalty estimates are conservative, consistent with the NRC staffs SE for NEI 06-09.

Justify that the SCDF and SLERF penalty estimates are conservative based on the results and insights from change-in-risk calculations for the proposed RICTs using the Hatch SPRA, including the impact of the portable FLEX equipment.

QUESTION 13 (APLC) - Tornado Missiles Section 2.3.1, Item 7, of NEI 06-09 states that the impact of other external events risk shall be addressed in the RMTS program, and explains that one method to do this is by documenting, prior to the RMTS program, that the external events that are not modeled in the PRA are not significant contributors to configuration risk. The SE for NEI 06-09 states that [o]ther external events are also treated quantitatively, unless it is demonstrated that these risk sources are insignificant contributors to configuration-specific risk.

Table E4-4 of Enclosure 4 to the LAR indicates that the tornado-generated missile hazard is screened based on criteria C1 (Event damage potential is < events for which plant is designed) of Table E4-5. Section 3 of Enclosure 4 to the LAR indicates that two non-conformances were identified, with one being corrected with a plant modification and the other, associated with service water systems, was evaluated and screened. However, the NRC staff reviewed a document, Plant Hatch Tornado Missile Project Summary Report, made available on the audit portal [SNC826314], which states that a Tornado Missile Risk Evaluation (TMRE) will need to be performed to conservatively estimate the risk of the remaining unprotected SSCs from tornado-generated missiles. The NRC staff notes that this risk appears to be related to beyond design basis events and that no TMRE documentation was provided in the application process. Therefore, address the following:

a) Clarify if a TMRE was conducted for the tornado-generated missile vulnerabilities that were not addressed by a plant modification. If completed, then provide the results and conclusions of that evaluation.

b) Alternatively, to Part (a), provide justification that an evaluation of risk associated with the unprotected SSCs from tornado-generated missiles is not required to screen this hazard.

c) Explain how the C1 screening for tornado-generated missile hazard is appropriate when the hazard appears to include beyond design basis risk.

d) If the screening criteria cited in the LAR is not sufficient to screen the tornado-generated missile hazard from consideration for impact on the RICTs for all plant configurations encompassed in the RICT program, then justify screening the tornado-generated hazard using another basis.

e) If it cannot be justified that the tornado-generated missile hazard can be screened for impact on the RICT calculations, then explain how the RICT program will mitigate or prevent the impact of the tornado-generated missile hazard during a RICT application.

Technical Specifications Branch (STSB) Audit Questions QUESTION 14 (STSB)

The following TS are listed as variations in the cross-reference table (Table E1-2) but are not listed in the variation section, Section 2.3, of the LAR. The NRC staff notes that these TS are not in TSTF-505 and should be listed under number 4 in Section 2.3, where it is stated that there is one Hatch TS SNC is proposing to apply the RICT program to. There are 5 total including 3.6.2.5, which is currently listed in the variation section.

3.5.1.C.1 3.7.2.D.1 3.8.7.A.1 3.8.7.B.1 QUESTION 15 (STSB)

The NRC staff noted the following editorial items in Attachment 3 (Bases mark-up):

For Unit 1, TS 3.5.1, Actions D.1, D.2, and D.3, second sentence should state: at least MODE 2 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, instead of.at least MODE 2 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, For both units, TS 3.6.1.3, Actions A.1, A.2, and A.3: Does a reference need made to the Note in the TS stating not applicable to main steam-line for Action A.1?

For Unit 2, TS 3.5.1, Actions E.1 and E.2, first sentence licensee inadvertently deleted the I in If.

For Unit 2, TS 3.8.1, page 3.8-18, formatting needs fixed at the top.

QUESTION 16 (STSB)

For Hatch, Unit 2, TS 3.5.1, ECCS [emergency core cooling system] - Operating, LCO 3.5.1, Each ECCS injection/spray subsystem and the Automatic Depressurization System (ADS) function of six of seven safety/relief valves shall be OPERABLE, Condition B is missing from pages 3.5-1 and 3.5-2 (pages 77 and 78 out of 401 pages in the application).

It appears that Condition B will remain as it is written in the current TS; however, based on pages 77 and 78 in the application, Condition B would be deleted. Please verify that Condition B will remain as written in the current plant TS and provide revised TS pages indicating such.

QUESTION 17 (STSB)

The TSTF-505, Revision 2 (ADAMS Accession No. ML18183A493), does not allow for TS loss of function conditions (i.e., those conditions that represent a loss of a specified safety function or inoperability of all required trains of a system required to be operable) in the risk informed completion time program.

Based on the design success criteria provided in the license amendment request Table E1-1, it appears that some proposed LCO Actions may constitute a loss of function. See the following questions related to the table.

a. The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.5.1 Condition E a condition with HPCI [high pressure coolant injection] system inoperable. The corresponding column of the SSCs Addressed by TS Condition indicates HPCI system, and the column of Design Success Criteria indicates one train (not credited in loss-of-coolant accident (LOCA) safety analysis).

Clarify for TS 3.5.1.E Condition with HPCI system inoperable, that the Design Success Criteria is reactor core isolation cooling (RCIC) is operable and ECCS injection/spray subsystems are operable. Discuss the analysis of record (AOR) that demonstrated adequacy of RCIC and ECCS injection/spray subsystems for ensuring adequate core cooling and reference the NRC documents approving the AOR of the concern or address the acceptability of the AOR if it was not previously approved by the NRC.

b. The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.5.1 Condition F a condition with HPCI system inoperable AND Condition A entered. The corresponding column of the SSCs Addressed by TS Condition indicates HPCI system and emergency core cooling system injection/spray, and the column of Design Success Criteria indicates one of two core spray subsystems and one LPCI [low pressure coolant injection] pump in each LPCI subsystem and one train (not credited in LOCA safety analysis).

Clarify for TS 3.5.1.F Condition with HPCI system inoperable and Condition A entered, that the Design Success Criteria is the remaining low pressure ECCS subsystems in conjunction with ADS are operable. Discuss the AOR that demonstrated adequacy of the low pressure ECCS injection/spray subsystems in conjunction with ADS for ensuring adequate core cooling and reference the NRC documents approving the AOR of the concern or address the acceptability of the AOR if it was not previously approved by the NRC.

c. The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.5.3 Condition A a condition with RCIC system inoperable. The corresponding column of the SSCs Addressed by TS Condition indicates RCIC system, and the column of Design Success Criteria indicates one train (not credited in safety analysis).

Clarify for TS 3.5.1.A Condition with one train of RCIC inoperable, that the Design Success Criteria is HPCI is operable. Discuss the AOR that demonstrated adequacy of HPCI for ensuring overall plant capability to provide makeup inventory at high reactor pressure and reference the NRC documents approving the AOR of the concern or address the acceptability of the AOR if it was not previously approved by the NRC.

QUESTION 18 (STSB)

TSTF-505, Revision 2 (ADAMS Accession No. ML18183A493), does not allow for TS loss of function conditions (i.e., those conditions that represent a loss of a specified safety function or inoperability of all required trains of a system required to be operable) in the risk informed completion time program.

Based on the design success criteria provided in the license amendment request Table E1-1, it appears that some LCO Actions may constitute a loss of function. See the following question related to the table.

The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.8.1 Condition D a condition with two or more required offsite circuits inoperable. The column of Design Success Criteria indicates the minimum diesel generators as one unit diesel generator (DG) and the swing DG OR two unit DGs AND one opposite unit DG capable of supplying power to one standby gas treatment (SGT) subsystem AND two DGs, each capable of supplying power to one unit LPCI valve load center. Given LCO 3.8.1 has multiple alternating current (AC) electrical sources required to be operable, please explain whether the DGs can provide the necessary power needed for all AC electrical sources listed in your LCO if you lose offsite power.

QUESTION 19 (STSB)

TSTF-505, Revision 2 (ADAMS Accession No. ML18183A493), does not allow for TS loss of function conditions (i.e., those conditions that represent a loss of a specified safety function or inoperability of all required trains of a system required to be operable) in the risk informed completion time program.

Based on the design success criteria provided in the license amendment request Table E1-1, it appears that some LCO Actions may constitute a loss of function. See the following questions related to the table.

a. The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.8.4 Condition A a condition with swing DG direct current (DC) electrical power subsystem inoperable due to performance of SR 3.8.4.3 or SR 3.8.6.6 OR one or more required opposite unit DG DC electrical power subsystems inoperable. The column of Design Success Criteria indicates one unit DG DC and the swing DG DC OR two unit DG DC; AND opposite unit DG DC capable of supplying power to support the required SGT safety function and required DGs to support design basis accident (DBA) and transient analysis. If more than one opposite unit DG DC electrical power subsystems are inoperable, this appears to be a loss of function (LOF). Please explain why it is not and if it is, please add the note not applicable when a LOF occurs, consistent with TSTF-505.

b. The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.8.4 Condition D a condition with one or more required Unit station service DC battery chargers on one subsystem inoperable. The column of Design Success Criteria indicates one unit station service DC electrical power subsystem. If more than one unit station service DC battery chargers on one subsystem are inoperable, this appears to be a LOF. Please explain why it is not and if it is, please add the note not applicable when a LOF occurs, consistent with TSTF-505.

QUESTION 20 (STSB)

The LAR, Enclosure 1, Table E1-2 includes a TSTF-505 cross reference to associated Hatch TS.

1) For TS 3.8.4, Condition A and D, the licensee states that a loss of function may occur.

Please discuss how TS 3.8.4, Condition G will alleviate the LOF in Condition A and D and why a Note is not required. Without a Note in Condition A and D, please explain how an operator would be aware not to use the RICT Program when there is a LOF.

2) TS 3.8.4, Condition A is applicable for DG DC electrical power subsystems and TS 3.8.4, Condition G is applicable for DC electrical power subsystems. Please confirm whether TS 3.8.4, Condition G is applicable for DG DC electrical power subsystems.

3) Additionally, please confirm whether Unit 1 TS 3.8.4, Condition G is applicable to Unit 2 electrical power subsystems.

QUESTION 21 (STSB)

TSTF-505, Revision 2 (ADAMS Accession No. ML18183A493), does not allow for TS loss of function conditions (i.e., those conditions that represent a loss of a specified safety function or inoperability of all required trains of a system required to be operable) in the risk informed completion time program.

Based on the design success criteria provided in the license amendment request Table E1-1, it appears that some LCO Actions may constitute a loss of function. See the following questions related to the table.

a. The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.8.7 Condition A a condition with one or more required opposite unit AC or DC electrical power distribution subsystems inoperable. The column of Design Success Criteria indicates opposite unit AC and DC electrical power distribution subsystem(s) needed to support minimum equipment. If more than one required opposite unit AC or DC electrical power distribution subsystems are inoperable, this appears to be a LOF. Please explain why it is not and if it is, please add the note not applicable when a LOF occurs, consistent with TSTF-505.

b. The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.8.7 Condition B a condition with one or more (Unit or swing bus) DG DC electrical power distribution subsystems inoperable. The column of Design Success Criteria indicates one unit or swing DG DC electrical power distribution subsystem. If more than one unit or swing bus DG DC electrical power distribution subsystems are inoperable, this appears to be a LOF. Please explain why it is not and if it is, please add the note not applicable when a LOF occurs, consistent with TSTF-505.

c. The LAR, Enclosure 1, Table E1-1 lists in the column of TS 3.8.7 Condition C a condition with one or more (Unit or swing bus) AC electrical power distribution subsystems inoperable.

The column of Design Success Criteria indicates one unit or swing AC electrical power subsystem. If more than one unit or swing bus AC electrical power distribution subsystems are inoperable, this appears to be a LOF. Please explain why it is not and if it is, please add the note not applicable when a LOF occurs, consistent with TSTF-505.

QUESTION 22 (STSB)

The LAR, Enclosure 1, Table E1-2 includes a TSTF-505 cross reference to associated HNP TS.

For TS 3.8.7, Condition A, B and C, the licensee states that a loss of function may occur.

Please discuss how TS 3.8.7, Condition F will alleviate the loss of function in Condition A, B and C and why a Note is not required. Without a Note in Condition A, B and C, please explain how an operator would be aware not to use the RICT Program when there is a loss of function.

QUESTION 23 (STSB)

The proposed administrative controls for the RICT Program in TS 5.5.16 paragraph e of of the LAR were based on the TS markups of TSTF-505, Revision 2 for Hatch.

The NRC staff recognizes that the model SE for TSTF-505, Revision 2 contains improved phrasing for the administrative controls for the RICT Program in TS 5.5.16 paragraph e, namely the phrasing approved for use with this program instead of used to support this license amendment. Please clarify the original phrasing in TS 5.5.16 paragraph e, and discuss whether the phrases used to support Amendment # xxx or, as discussed in the TSTF-505 model SE, approved for use with this program would provide more clarity for this paragraph.

Electrical Engineering Branch (EEEB) Audit Questions QUESTION 24 (EEEB)

For TSTF-505, the design success criterion is a minimum set of the remaining required equipment that has the capacity and capability to provide the TS safety function.

a. In Table E1-1 of Enclosure 1 of the LAR, the licensee stated the design success criteria for TS 3.8.1, Condition A (One required offsite circuit inoperable). Hatch has three offsite power circuits and the design success criteria for TS 3.8.1, Condition A does not address the second and third offsite power circuit. Please explain what happens to the second and third offsite power circuit when you have one required offsite circuit inoperable for TS 3.8.1, Condition A design success criteria.

QUESTION 25 (EEEB)

In TS Bases 3.8.4, for Unit 1, the licensee states that some components required by Unit 1 require power from Unit 2 sources (e.g., SGT System and LPCI valve load centers). For Unit 2, the licensee states that some components required by Unit 2 require power from Unit 1 sources (e.g., SGT System, LPCI valve load centers, Main Control Room Environmental Control (MCREC) System, and Control Room Air Condition (AC) System).

The design success criterion for TS 3.8.4, Condition A, B, and C, the licensee states opposite unit DG DC capable of supplying power to support the required SGT (and for Unit 2, Unit 1 MCREC and Control Room AC safety function and required DGs to support DBA and transient analyses.

a. Please explain why LPCI valve load centers would not be included for TS 3.8.4, Condition A, B, and C design success criterion.

b. Provide clarification whether the MCREC and Control Room AC requires power from Unit 2 sources.

QUESTION 26 (EEEB)

In the column, LCO ACTION TSTF-505/HATCH 1&2 TS of Table E1-4 of Enclosure 1-4, the licensee provided the RICT estimate for LCO 3.8.7, Required Action A.1 and LCO 3.8.7, Required Action B.1. Additionally, the licensee provided the RICT estimate for LCO 3.8.7, Required Actions A.1 and C.1, and LCO 3.8.7, Required Actions A.1, B.1 and D.1.

a. Please discuss whether LCO 3.8.7, Required Action A.1 and LCO 3.8.7, Required Action B.1 has multiple RICT estimate.

b. Please explain why LCO 3.8.7, Required Action A.1 has been added together with RICT estimate for LCO 3.8.7, Required Actions A.1 and C.1 and LCO 3.8.7, Required Actions A.1, B.1 and D.1. in Table E1-4 of Enclosure 1-4.

c. Please explain why LCO 3.8.7, Required Action B.1 has been added together with RICT estimate for LCO 3.8.7, Required Actions A.1, B.1 and D.1 in Table E1-4 of -4.

QUESTION 27 (EEEB)

In the LAR, Enclosure 12, Risk Management Action (RMA) Examples, the licensee stated that for TS 3.8.1 Condition A.3, one required offsite circuit inoperable, the sample calculated RICT provided in Enclosure 1 is on the order of 7.7 days. However, in Table E1-4 of Enclosure 1-4, the licensee stated that for TS 3.8.1 Condition A.3 the RICT estimate is 30 days. Please explain the inconsistency in the RICT estimate for TS 3.8.1 Condition A.3.

QUESTION 28 (EEEB)

In the LAR, Enclosure 12, the licensee provided example RMAs for emergent scenario for all TS Condition for TS 3.8.1, TS 3.8.4, and TS 3.8.7. However, in Table E1-4 of Enclosure 1-4, the licensee provided emergent RICT for TS 3.8.1 Condition E, and TS 3.8.7 Condition B, C and D. Provide clarification whether the remaining TS Condition for TS 3.8.1, TS 3.8.4, and TS 3.8.7 in Table E1-4 of Enclosure 1-4 have emergent RICT.

QUESTION 29 (EEEB)

In the LAR, Enclosure 12, the licensee states that for TS 3.8.7 Condition C, one or more (same Unit or swing bus) DG DC electrical power distribution subsystems inoperable, the sample calculated RICT provided in Enclosure 1 is on the order of 45.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> for an emergent RICT.

However, in Table E1-1 of Enclosure 1 of the LAR, the licensee states TS 3.8.7 Condition C, one or more (Unit or swing bus) AC electrical power distribution subsystems inoperable. Please verify whether TS 3.8.7 Condition C is for AC or DG DC electrical power distribution subsystems.

ML22048C223 OFFICE NRR/DORL/LPL2-1/PM NRR/DORL/LPL2-1/LA NRR/DRA/APLA/BC NAME JLamb KGoldstein RPascarelli DATE 2/16/2022 02/18/2022 2/24/2022 OFFICE NRR/DORL/LPL2-1/BC NRR/DORL/LPL2-1/PM NAME MMarkley JLamb DATE 3/1/2022 3/1/2022