ML18267A171

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NRR E-mail Capture - Final RAI from PRA Branch: Revise Technical Specifications to Increase Inverter AOT Extension (L-2018-LLA-0140)
ML18267A171
Person / Time
Site: Salem  PSEG icon.png
Issue date: 09/21/2018
From: James Kim
Plant Licensing Branch 1
To: Duke P, Bernard Thomas
Public Service Enterprise Group
References
L-2018-LLA-0140
Download: ML18267A171 (5)
v • d • e


Text

NRR-DMPSPEm Resource From: Kim, James Sent: Friday, September 21, 2018 4:05 PM To: Duke, Paul R.; Thomas, Brian J.

Cc: Marabella, Lee A.

Subject:

Salem 1 and 2 - Final RAI from PRA Branch RE: Inverter AOT Extension Attachments: Salem AOT-Revised Final RAI from PRA Branch.docx By letter dated May 16, 2018, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18136A866), as supplemented by letter dated June 14, 2018 (ML18169A218), PSEG Nuclear LLC (PSEG, the licensee), requested an amendment to Renewed Facility Operating License No. DPR-70 and DPR-75 for Salem Generating Station (Salem) Units 1 and 2. This license amendment request proposes to change Technical Specification (TS) 3.8.2.1, "A. C. Distribution - Operating." The proposed change would increase the Vital Instrument Bus (VI B) Inverters allowed outage time (AOT) from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for the A, B and C inverters to 7 days and from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for the D inverter to 7 days.

The NRC staff from Instrumentation and Controls Branch has determined that the additional information is required for the staff to complete its review. On September 6, 2018, the NRC staff sent PSEG the draft Request for Additional Information (RAI). This RAI relates to the licensees request to increase the Vital Instrument Bus (VIB) Inverters allowed outage time (AOT).

On September 18, 2018, the NRC staff and the licensee held a conference call to clarify the request. During the conference, it was agreed that a revised RAI will be provided. On September 20, 2018, the NRC staff sent PSEG the revised RAI. Subsequently, the licensee agreed to respond to this request within 30 days of this email. A publicly available version of this final RAI (attached) will be placed in the NRCs ADAMS.

Jim Kim Project Manager - Salem Generating Station NRR/DORL/LPL1 301-415-4125 1

Hearing Identifier: NRR_DMPS Email Number: 585 Mail Envelope Properties (James.Kim@nrc.gov20180921160400)

Subject:

Salem 1 and 2 - Final RAI from PRA Branch RE: Inverter AOT Extension Sent Date: 9/21/2018 4:04:55 PM Received Date: 9/21/2018 4:04:00 PM From: Kim, James Created By: James.Kim@nrc.gov Recipients:

"Marabella, Lee A." <Lee.Marabella@pseg.com>

Tracking Status: None "Duke, Paul R." <Paul.Duke@pseg.com>

Tracking Status: None "Thomas, Brian J." <Brian.Thomas@pseg.com>

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 1572 9/21/2018 4:04:00 PM Salem AOT-Revised Final RAI from PRA Branch.docx 24603 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

REVISED REQUEST FOR ADDITIONAL INFORMATION BY THE PROBABILISTIC RISK ASSESSMENT LICENSING BRANCH, DIVISION OF RISK ASSESSMENT LICENSE AMENDMENT REQUEST FOR EXTENSION OF VITAL INSTRUMENT BUS INVERTER ALLOWED OUTAGE TIMES PSEG NUCLEAR LLC SALEM NUCLEAR GENERATING STATION UNITS 1 AND 2 DOCKET NOS. 50-272 AND 50-311 (EPID: L-2018-LLA-0140)

By letter dated May 16, 2018, as supplemented by letter dated June 14, 2018 (Agencywide Documents Access and Management System (ADAMS) Accession Numbers ML18136A866 and ML18169A218, respectively), Public Service Enterprise Group Nuclear, LCC (PSEG, the licensee), submitted a license amendment request (LAR) regarding the Salem Nuclear Generating Station Units 1 and 2. The proposed amendment would change technical specification (TS) 3.8.2.1, A.C. [alternating current] Distribution - Operating, that would increase the vital instrument bus inverter allowed outage time (AOT) from 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to 7 days for the A, B and C inverters and from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days for the D inverter. The licensee states that the proposed change will allow increased flexibility in the scheduling and performance of corrective maintenance, allow better control and allocation of resources, and reduce the potential for unplanned plant shutdowns.

The Probabilistic Risk Assessment (PRA) Licensing Branch (APLA) of the Division of Risk Assessment staff has reviewed the LAR and determined that additional information, related to PRA considerations described in the LAR, is required for the APLA staff to complete the review.

A request for additional information (RAI) memorandum was provided to the Division of Operating Reactor Licensing on August 23, 2018. Subsequently, a clarification call was held with the licensee and NRC staff on September 18, 2018, and clarifications to the RAI questions were determined to be appropriate. The revised RAI questions are provided below.

Regulatory Basis Title 10 of the Code of Federal Regulations (10 CFR) Part 50.65, "Requirements for monitoring the effectiveness of maintenance at nuclear power plants," requires that preventive maintenance activities must be sufficient to provide reasonable assurance that Structures Systems and Components are capable of fulfilling their intended functions. As it relates to the proposed inverter AOT extension, 10 CFR 50.65(a)(4) requires the assessment and management of the increase in risk that may result from proposed maintenance activities.

10 CFR 50.63, "Loss of all alternating current power," requires that nuclear power plants must be able to withstand a loss of all A.C. power for an established period of time and recover from a station blackout.

Enclosure

The following are applicable regulatory guidelines and policy documents for evaluating the risk impact of the proposed change:

  • RG 1.177, Revision 1 (May 2011), "An Approach for Plant-Specific, Risk-Informed Decision-making: Technical Specifications," describes an acceptable risk-informed approach for assessing proposed permanent TS changes in AOTs. In addition, this RG provides risk acceptance guidelines for evaluating the results of such assessments.
  • RG 1.200, Revision 2 (March 2009), An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities, describes an acceptable approach for determining whether the quality of the PRA models, in total or the parts that are used to support an application, is sufficient to provide confidence in the results, such that the PRA models can be used in regulatory decision making for light-water reactors.

Request For Additional Information APLA RAI-1 In order to ensure efficiency in its reviews and prevent duplicate reviews of a licensees PRA technical acceptability, the NRC staff may utilize PRA information from the licensees previous risk-informed submittals. In the course of its review for this LAR, the staff utilized information from the licensees application for Salem containment fan cooler unit AOT extension dated March 6, 2017 (ADAMS Accession Number ML17065A241), as supplemented by letters dated May 4, 2017 (ADAMS Accession Number ML17125A051) and September 14, 2017 (ADAMS Accession Number ML17257A439). The method used by the licensee for estimating core damage frequency (CDF) for fire and seismic events in the supplemental letter dated May 4, 2017, differs from the method used in the current LAR dated May 16, 2018 (ADAMS Accession Number ML18136A866). The NRC staff performed a confirmatory calculation based on the method used in the May 4, 2017 letter. The resulting value for CDF for fires corresponded to Region II RG 1.74 acceptance criteria. As a result, the licensees conclusion in Section 3.2.3.2 of the current LAR that since the change in CDF is negligible, the large early release frequency (LERF) impact will also be negligible would not be valid per the confirmatory calculation, as a change in CDF corresponding to Region II of RG 1.74 is not considered negligible.

Alternate Fire Event Calculations for Salem Inverter D Calculation of CDFsurrogate:

CDFsurrogate = FIE-F x UAINV x PBU x (TAOT/TCYC) = 2.51E-06 / reactor-year where:

FIE-F = fire initiating event frequency = 4.62E-01 UAINV = Unavailability of inverter D = 1.0 PBU = Probability of backup power failure = 2.83E-04 TAOT = AOT duration = 7 days TCYC = cycle duration = 365 days TAOT/TCYC = Fractional Unavailability Per the NRC alternate calculations above, the values determined for CDFsurrogate correspond to Region II RG 1.74 acceptance criteria. This is a less conservative result than that reported in Section 3.2.3.2 of the licensees LAR dated May 16, 2018.

RAI-1

Please provide a discussion explaining the use of the two different calculation methods and the rationale for the acceptability of the fire PRA approach used in the LAR dated May 16, 2018, as opposed to the method used in the letter dated May 4, 2017, and the basis for the determination that this approach is sufficiently conservative to support the proposed inverter AOT extension.

In addition, provide an evaluation of the LERF from fire events.

APLA RAI-2 The entry for item (l) in Table A-7 of Attachment 2 to the LAR dated May 16, 2018, notes that the Salem PRA Model of Record (MOR) (SA115A) was only completed for Salem Unit 1 and it relies on Unit 2 equipment for certain support functions.

RAI-2

Please provide justification that the cross-unit support functions, as well as the asymmetries, in the Salem PRA MOR (SA115A) are adequately accounted for such that application to Salem Unit 2 is appropriate.

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