ML15111A429

Palo Verde Nuclear Generating Station Unit 3, American Society of Mechanical Engineers (ASME) Code, Section Xi, Request for Approval of an Alternative to Flaw Removal - Relief Request 53

ML15111A429
Person / Time
Site:	Palo Verde
Issue date:	04/17/2015
From:	Cadogan J J Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML15111A422	List: ML15111A429 ML15111A430
References
102-07034-JJC/DCE
Download: ML15111A429 (10)

Text

10 CFR 50 55a,a psJohn 3 Cadogan, JrVice PresidentNuclear EngineeringPalo VerdeNuclear Generating StationP 0 Box 52034Phoenix AZ 85072Mail Station 7602Tel 623 393 4083102-07034-JJC/DCEApril 17, 2015ATTN Document Control DeskU S Nuclear Regulatory CommissionWashington, DC 20555-0001ReferenceAPS letter number 102-07037, Palo Verde Nuclear Generating StationUnit 3, Docket No STN 50-530, Transmittal of Proprietary Documentsfor Relief Request 53, dated April 17, 2015

Dear SirsSubjectPalo Verde Nuclear Generating Station (PVNGS)Unit 3Docket No 50-530American Society of Mechanical Engineers (ASME) Code,

Section XI, Request for Approval of an Alternative to FlawRemoval -Relief Request 53Pursuant to 10 CFR 50 55a(z)(1), Arizona Public Service Company (APS) requestsNRC approval of Relief Request 53, which proposes an alternative to the ASME Coderequirements of Section XI related to flaw indications identified in a Unit 3 reactorcoolant pump 2A suction pressure instrument nozzle Specifically, APS is proposing ahalf-nozzle repair and flaw evaluation which provides an acceptable level of qualityand safety as an alternative to the IWA-4421 requirements for flaw removal Theduration of this relief request is for one operating fuel cycleThe referenced letter provides proprietary documents that were submitted to theNRC in support of this relief requestNo commitments are being made to the NRC by this letterAPS requests approval of this relief request prior to startup from the Unit 3eighteenth refueling outage currently scheduled for April 30, 2015Should you need further information regarding this relief request, please contactThomas Weber, Regulatory Affairs Department Leader at (623) 393-5764/\041~A member of the STARS (Strategic Teaming and Resource Sharing) AllianceCallaway Diablo Canyon Palo Verde Wolf Creek ATTN Document Control DeskU S Nuclear Regulatory CommissionASME Code,Section XI, Request for Approval of an Alternative to Flaw Removal -Relief Request 53Page 2Sincerely,JJC//DCE/hscEnclosure Relief Request 53 Proposed Alternative in Accordance with10 CFR 50 55a(z)(1)cc M L DapasM M WatfordC A PeabodyNRC Region IV Regional AdministratorNRC NRR Project Manager for PVNGSNRC Senior Resident Inspector for PVNGS EnclosureRelief Request 53 Proposed Alternative in Accordance with10 CFR 50 55a(z)(1)ATTACHMENTSAttachment 1 -RCP Instrumentation Nozzle Repair SchematicAttachment 2 -Flaw Fracture Mechanics, Corrosion, and Loose Parts Evaluations forOne Cycle Relief (DAR-MRCDA-15-6-NP)Attachment 3 -APS Response to NRC Request for Additional Information (RAI), datedApril 14, 2015 EnclosureBackground InformationOn April 7, 2015, evidence of leakage was found during post-shutdown boric acidwalkdowns at the Palo Verde Nuclear Generating Station (PVNGS) Unit 3 reactorcoolant pump (RCP) 2A suction pressure instrument nozzle In response, on April 8,2015, a visual examination of the nozzle was conducted in accordance with theAmerican Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel CodeCase N-722-1, Additional Examinations for PWR Pressure Retaining Welds in Class 1Components Fabricated With Alloy 600/82/182 Materials, Section Xl, Division 1 APSdetermined the indication to be reactor coolant system (RCS) pressure boundaryleakage based on the resultsThe RCP 2A suction instrument nozzle was an Alloy 600, 1-inch nominal pipe size, thatcontained an internal orifice designed to limit RCS leakage to within the capacity of thecharging system in the event of a connected instrument line break The nozzle extendsthrough the approximate 3-inch RCP suction safe end pipe wall to connect to itsassociated instrument piping A J-groove weld that connects the suction instrumentnozzle to the safe end pipe wall inner surface provided the original RCS pressureboundary The ASME Code Section III Class 1 boundary was originally located at theinternal orifice within the suction instrument nozzleThe RCP 2A suction instrument nozzle is one of twenty Unit 3 RCS cold leg instrumentnozzles inspected in accordance with Table 1, Item BP-1 5 205, of ASME Code Case N-722-1 Subsequent to the visual examination performed on April 8, 2015, the scopewas expanded to visually examine the remaining 19 RCS cold leg instrument nozzles inaccordance with Note 7 of Code Case N-722-1, Table 1 The results were found to beacceptableDuring the repair of the nozzle, Arizona Public Service Company (APS) performedsupplemental inspections in an attempt to obtain information regarding the as-foundcondition of the suction pressure instrument nozzle These supplemental inspectionsincluded* A dam was installed to allow introduction of liquid penetrant into the annulus of thecut nozzle The penetrant was allowed to soak for approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> and theinternal nozzle bore and the inside face of the J-groove weld were then examinedvisually with a borescope for any evidence of penetrant migration" A straight beam ultrasonic test (UT) through the nozzle wall from the cut end wasperformed to detect circumferential flaws in the nozzle wall A mockup of the nozzlewas used to calibrate the UT process prior to the examination* After boring out a portion of the nozzle for the repair, additional internal visualexaminations were performed using a borescopeThe visual and dye penetrant inspections did not identify signs of degradation or thesource of the leak The straight beam UT did not identify evidence of circumferentialflaws at any depth in the nozzle The results were not unexpected given the likelihoodof axially oriented SCC EnclosureAn ASME Code compliant half-nozzle repair was implemented to replace the originalfunction of the J-groove weld on the interior of the safe end wall The replacement half-nozzle consists of a forged, primary water stress corrosion cracking (PWSCC) resistantAlloy 690 drilled round bar stock attached by an external J-groove weld with a fillet weldcap The half-nozzle repair effectively transfers the Class 1 reactor coolant pressureboundary weld from the original internal J-groove weld in the RCP carbon steel safe endto a new external J-groove weld The replacement half-nozzle contains an internalorifice and integral 90 degree elbow that functionally replaces the original restrictionorifice The inner portion of the original RCP 2A suction instrument nozzle and the J-groove weld (remnant nozzle and remnant weld) will remain in place In summary, therepair relocated the RCS pressure boundary from the RCP 2A suction instrumentnozzle remnant J-groove weld to a new exterior J-groove weld Additionally, the ASMECode Class 1 boundary was relocated from the remnant nozzle internal orifice to thereplacement nozzle orificeThe Enclosure includes the following attachments* Attachment 1- RCP Instrumentation Nozzle Repair Schematic" Attachment 2 -Flaw Fracture Mechanics, Corrosion, and Loose Parts Evaluationsfor One Cycle Relief (DAR-MRCDA- 15-6-NP)" Attachment 3 -APS Response to NRC Request for Additional Information (RAI),dated April 14, 20152 Enclosure1 ASME Code Components AffectedComponents RCP 2A Suction Pressure Instrument NozzleCode Class Class 1Examination Category B-P (Class 1 PWR Components Containing Alloy600/82/182)Code Item Number B15 205Description Reactor Coolant System Cold Leg InstrumentSize 1 inch Nominal Pipe Size at the RCP 2A Suction PressureInstrument Nozzle J-groove WeldMaterial SB-1 66 Alloy 600 Nozzle and ERNiCr-3/ENiCrFe-3 Alloy82/182 Butter and Weld2 Applicable Code Edition and AddendaPVNGS, Unit No 3, Inservice Inspection Program (ISI) -Third Interval, ending January11, 2018 ASME B&PV,Section XI, 2001 Edition including Addenda through 2003(Reference 1) as supplemented by 10 CFR 50 55a(g)(6)(ii)(E), Reactor CoolantPressure Boundary Visual Inspections3 Applicable Code RequirementsSection XI, Article IWA-4000 provides requirements for repair/replacement activitiesIWA-4421 states, in partDefects shall be removed or mitigated in accordance with the followingrequirementsThe following Section XI articles are not applicable because they are exempted byArticle IWB-1220(b)(1), as addressed by 10 CFR 50 55a(g)(6)(ii)(E)(2) and Code CaseN-722-1 since the nominal pipe size of the nozzle is one inch or lessSection Xl, Article IWA-3000 provides standards for examination evaluationIWA-31 00(a) states, in partEvaluation shall be made of flaws detected during an Inservice examination asrequired by IWB-3000 for Class 1 pressure retaining components3 EnclosureIWA-3300(b) states, in partFlaws shall be characterized in accordance with IWA-331 0 through IWA-3390,as applicableSection Xl, Article IWB-3000 provides acceptance standards for Class 1 componentsIWB-3420 statesEach detected flaw or group of flaws shall be characterized by the rules of IWA-3300 to establish the dimensions of the flaws These dimensions shall be usedin conjunction with the acceptance standards of IWB-35004 Reason for RequestAPS conducted boric acid walkdowns inside the containment building at the beginningof the PVNGS Unit 3 18th Refueling Outage (3R1 8) These walkdowns revealedevidence of leakage in the annulus at the RCP 2A suction safe end pressure instrumentnozzle (suction instrument nozzle) Subsequent visual examination confirmed reactorcoolant as the sourceVisual examinations of the remaining Unit 3 RCS cold leg instrument nozzles wereperformed as required by Code Case N-722-1 with no evidence of RCS pressureboundary leakage identifiedRepair of the original RCP 2A instrument nozzle and J-groove weld would requireremoval of the RCP internals to access the internal surface of the reactor coolant pipingin order to grind out the attachment weld and repair or replace the remaining nozzleSuch an activity would result in high radiation exposure to the personnel involved andpresent the additional risk of introducing foreign material into the RCS and reactor coreAdditionally, volumetric UT examination of the remnant J-groove weld was not feasiblebecause of its configuration and the restrictive access associated with the small bore ofthe instrument nozzle internal orificeA half-nozzle design repair was implemented such that the original RCP 2A instrumentnozzle and J-groove weld no longer perform a pressure boundary function APS isproposing a half-nozzle repair and a flaw evaluation as an alternative to the IWA-4421requirements for flaw removal5 Proposed Alternative and Basis for UseAPS is proposing an alternative in accordance with 10 CFR 50 55a(z)(1) Thealternative consists of two main elementsa ASME Code Compliant Half-Nozzle Repair4 EnclosureThe half-nozzle repair is an industry standard, ASME Code compliant repair methodthat attaches a new PWSCC resistant Alloy 690 half-nozzle using an external Alloy52M partial penetration J-groove weld The repair relocated the pressure boundaryweld from the instrument nozzle J-groove weld on the interior wall of the RCPsuction nozzle safe end to the new exterior J-groove weld on the exterior wall Thehalf-nozzle repair of the RCP 2A suction nozzle penetration will not remove the flawsin the remnant J-groove weld or remnant Alloy 600 nozzle material near this weldThe half-nozzle repair is shown in Attachment 1 to this Enclosureb Flaw EvaluationThe flaw evaluation postulated a maximum bounding flaw that propagates axiallyand circumferentially through the J-groove weld and butter into the carbon steelbase material to a depth conservative with respect to one operating fuel cycleThe results of the evaluation were found to be acceptable and are summarized inAttachment 2, Flaw Fracture Mechanics, Corrosion, and Loose Parts Evaluations forOne Cycle Relief, to this EnclosureThe above two elements provide an acceptable level of quality and safety in accordancewith 10 CFR 50 55a(z)(1)6 Duration of Proposed AlternativeThe duration of the request is for the 19th Unit 3 operating fuel cycle ending in therefueling outage U3R1 9 The U3R1 9 refueling outage is currently scheduled for fall20167 PrecedentsPalo Verde Nuclear Generating Station, Units 1, 2, and 3 -10 CFR 50 55a(a)(3)(i)Alternative Repair Request for Reactor Coolant System Hot Leg Alloy 600 Small-BoreNozzles (Relief Request 31, Revision 1), August 16, 2005, ADAMS Accession NumberML 0525503688 ReferencesSection X1, Rules for Inservice Inspection of Nuclear Power Plant Components, 2001Edition, including Addenda through 20039 AttachmentsAttachment 1 -RCP Instrumentation Nozzle Repair SchematicAttachment 2 -Flaw Fracture Mechanics, Corrosion, and Loose Parts Evaluations forOne Cycle Relief (DAR-MRCDA- 15-6-NP)Attachment 3 -APS Response to NRC Request for Additional Information (RAI), datedApril 14, 20155 EnclosureATTACHMENT 1RCP Instrumentation Nozzle Repair Schematic EnclosureAttachment 1 -RCP Instrumentation Nozzle Repair SchematicRCP 2A RCP Instrumentation Nozzle Repair SchematicI