ML14038A076

Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, and 3 - Response to Request for Additional Information (RAI) Associated with Near-Term Task Force Recommendation 2.3, Flooding Walkdowns

ML14038A076
Person / Time
Site:	Palo Verde
Issue date:	01/31/2014
From:	Mims D C Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
102-06829-DCM/PJH
Download: ML14038A076 (6)

Text

10 CFR 50.54(f)QapsDWIGHT C. MIMSSenior Vice President, NuclearRegulatory

& Oversight Palo VerdeNuclear Generating StationP.O. Box 52034Phoenix, AZ 85072Mail Station 7605Tel 623 393 5403102-06829-DCM/PJH January 31, 2014ATTN: Document Control DeskU.S. Nuclear Regulatory Commission 11555 Rockville PikeRockville, MD 20852

References:

1. APS Letter 102-06627, Flooding Walkdown Report Requested byNRC Letter, Request for Information Pursuant to 77tie 10 of theCode of Federal Regulations 50.54(f)

Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insightsfrom the Fukushima Dai-ichi

Accident, dated November 27, 2012(ADAMS Accession No.: ML12334A416)

2. N RC Letter, Request for Additional Information Associated withNear-Term Task Force Recommendation 2.3, Flooding Walkdowns, dated December 23, 2013 (ADAMS Accession No.: ML13325A891)

Subject:

Palo Verde Nuclear Generating Station (PVNGS)Units 1, 2, and 3Docket Nos. STN 50-528, 50-529, and 50-530Response to Request for Additional Information (RAI)Associated with Near-Term Task Force Recommendation 2.3,Flooding Walkdowns On November 27, 2012, Arizona Public Service (APS) submitted Reference 1which provided the APS flooding walkdown submittal report in response toNear-Term Task Force Recommendation 2.3, Flooding Walkdowns, for PVNGS.This report is consistent with the flooding walkdown guidance described in NEI 12-07, Guidelines For Performing Verification Walkdowns Of Plant Flood Protection Features.

On December 23, 2013, the U. S. Nuclear Regulatory Commission (NRC) provided arequest for additional information (RAI) (Reference

2) associated with the APSflooding walkdown submittal report. The NRC requested that APS provide a responseby January 31, 2014. The enclosure to this letter provides the APS response to theRAI.A member of the STARS (Strategic Teaming and Resource Sharing)

AllianceCallaway

• Comanche Peak

• Diablo Canyon

• Palo Verde

• Wolf Creek 102-06829-DCM/PJH January 31, 2014ATTN: Document Control DeskU.S. Nuclear Regulatory Commission Request for Additional Information Associated with Near-Term Task Force Recommendation 2.3,Flooding Walkdowns Page 2No commitments are being made to the NRC by this letter. Should you need further information regarding this response, please contact Mark McGhee, Department Leader Nuclear Regulatory

Affairs, at (623) 393-4972.

I declare under penalty of perjury that the foregoing is true and correct.Executed on(Date)Sincerely, DCM/PJH/hsc

Enclosure:

Response to NRC RAI Associated with Flooding Walkdowns

-Review ofAvailable Physical Margin (APM) Assessments cc: E. J. LeedsM. L. DapasJ. K. RankinA. E. GeorgeM. A. BrownL. M. RegnerNRC Director Office of Nuclear Reactor Regulation NRC Region IV Regional Administrator NRC NRR Project ManagerNRC NRR Project ManagerNRC Senior Resident Inspector PVNGSNRC NRR/JLD/JPMB Project Manager ENCLOSURE Response to NRC RAI Associated with FloodingWalkdowns

-Review of Available PhysicalMargin (APM) Assessments Enclosure

-Response to NRC RAI Associated with FloodingWalkdowns

-Review of Available Physical Margin (APM) Assessments INTRODUCTION On March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) staff issued a letter(Agencywide Documents Access and Management System (ADAMS) Accession No. ML12053A340) requesting additional information per Title 10 of the Code of FederalRegulations, Section 50.54(f)

(hereafter called the 50.54(f) letter).

The 50.54(f) letterrequested that licensees conduct flooding hazard walkdowns to identify and address plant-specific

degraded, nonconforming, or unanalyzed conditions through the corrective actionprogram (CAP). All licensees stated by letter that the flooding walkdowns would beperformed in accordance with Nuclear Energy Institute (NEI) 12-07, Guidelines forPerforming Verification Walkdowns of Plant Flood Protection

Features, May 2012 (ADAMSAccession No. ML 12172A038).

Following the NRC staff's initial review of the reportsdocumenting the results of the licensees' walkdowns, regulatory site audits were conducted at a sample of plants. During the site audits the NRC staff observed that several licensees did not consistently determine and/or document available physical margin (APM) in amanner that met the expected interpretation of NEI 12-07. Based on the walkdown reportreviews and site audits, the NRC staff identified additional information necessary to allowthe NRC staff to complete its assessments.

By letter dated December 23, 2013, the NRCstaff provided a request for additional information (RAI) to Arizona Public Service Company(APS).This enclosure is the APS response to the RAI regarding flooding walkdowns.

The NRCinformation

requests, provided in the December 23, 2013 letter, are restated then followedby the APS response.

RAI Number 1 -Confirmation that the process for evaluating APM was reviewedAPS ResponseAPS confirms that the process used at Palo Verde Nuclear Generating Station (PVNGS) forevaluating available physical margin (APM) was reviewed as requested.

The APS review wasto ensure the process for APM determination and evaluation was consistent with theguidance in NEI 12-07.RAI Number 2 -Confirmation that the APM process is now or was alwaysconsistent with the guidance in NEI 12-07 and discussed in this RAIAPS ResponseAPS confirms that the APM process is now consistent with the guidance described in NEI 12-07. During the original flooding walkdown effort (under the NTTF Recommendation 2.3) itwas the intention of APS to follow the guidance provided in NEI 12-07 including defining theterm "small margin" in the original flooding walkdown report. Although the definition of"small margin" was not included in the original flooding walkdown report the definition wasagreed to in advance and contained in a proprietary vendor procedure.

This definition of"small margin" has now been added to the flooding walkdown report. The floodingwalkdown report has now been supplemented with a detailed spreadsheet that identifies theAPM values for flooding protection features.

As part of the original walkdown process APSentered into the PVNGS corrective action process those flooding protection features withI Enclosure

-Response to NRC RAI Associated with FloodingWalkdowns

-Review of Available Physical Margin (APM) Assessments small APMs and significant consequences.

The flooding walkdown report is maintained onsite for future audits and inspections.

RAI Number 3 -If changes are necessary, a general description of any processchanges to establish this consistency APS ResponseAs stated above, the original walkdown effort followed the guidance provided in NEI 12-07,including a definition for a "small margin."

Although no process changes were necessary, APS did supplement the flooding walkdown report as described in the response to RAINumber 2 above.RAI Number 4 -As a result of the audits and subsequent interactions with industryduring public meetings, NRC staff recognized that evaluation of APM for seals(e.g., flood doors, penetrations, flood gates, etc.) was challenging for somelicensees.

Generally, licensees were expected to use either Approach A orApproach B (described below) to determine the APM for seals:a) If seal pressure ratings were known, the seal ratings were used todetermine APM (similar to example 2 in Section 3.13 of NEI 12-07). Anumerical value for APM was documented.

No further action was performed if the APM value was greater than the pre-established small-margin threshold value. If the APM value was small, an assessment of "significant consequences" was performed and the guidance in NEI 12-07 Section 5.8was followed.

b) If the seal pressure rating was not known, the APM for seals in a floodbarrier is assumed to be greater than the pre-established small-margin threshold value if the following conditions were met: (1) the APM for thebarrier in which the seal is located is greater than the small-margin threshold value and there is evidence that the seals weredesigned/procured, installed, and controlled as flooding seals in accordance with the flooding licensing basis. Note that in order to determine that theseal has been controlled as a flooding seal, it was only necessary todetermine that the seal configuration has been governed by the plant'sdesign control process since installation.

In this case, the APM for the sealcould have been documented as "not small".As part of the RAI response, state if either Approach A or Approach B was used aspart of the initial walkdowns or as part of actions taken in response to this RAI. Noadditional actions are necessary if either Approach A or B was used.If neither Approach A or B was used to determine the APM values for seals (eitheras part of the walkdowns or as part of actions taken in response to this RAI), thenperform the following two actions:e Enter the condition into the CAP (note: it is acceptable to utilize a singleCAP entry to capture this issue for multiple seals). CAP disposition of"undetermined" APM values for seals should consider the guidance provided2 Enclosure

-Response to NRC RAI Associated with FloodingWalkdowns

-Review of Available Physical Margin (APM) Assessments in NEI 12-07, Section 5.8. The CAP disposition should confirm all seals canperform their intended safety function against floods up to the currentlicensing basis flood height. Disposition may occur as part of the Integrated Assessment.

If an Integrated Assessment is not performed, determine whether there are significant consequences associated with exceeding thecapacity of the seals and take interim action(s),

if necessary, via the CAPprocesses.

These actions do not need to be complete prior to the RAIresponse.

9 Report the APM as "undetermined" and provide the CAP reference in theRAI response.

APS ResponseDuring the original flooding walkdowns inspections were performed on plant floodingprotection features (roof and wall penetrations, piping penetrations, hatches and plugs,etc.) and non-design basis features.

If those features did not meet the pre-established small-margin threshold value for APM, the condition was entered into the PVNGS corrective action program.

At PVNGS, neither Approach A or B, as described in RAI number 4, wereused to determine the APM values for seals. Of the flooding protection features inspected inthe original flooding walkdowns, there is only one penetration seal that was identified duringthe RAI review that was documented as "undetermined."

This penetration seal is located in an exterior wall that is exposed to ground water. It is anabandoned original construction aid conduit in the west wall of the Unit 3 Auxiliary Buildingat the 54'-0" elevation.

The penetration seal for this conduit was inspected as part of theoriginal flooding walkdowns for signs of degradation.

It was discovered that the seal wasweeping water into the Unit 3 Auxiliary Building.

The degraded penetration seal was enteredinto the PVNGS corrective action program and the repair was completed (Work Ordernumber 4241431).

During the RAI review, the APM for this seal was documented as "undetermined" (PaloVerde Action Request [PVAR] number 4494502, dated January 16, 2014) and was recordedas such in the amended walkdown record forms.3