ML13063A033

Davis-Besse, Revised Reply to Request for Additional Information for the Review of License Renewal Application

ML13063A033
Person / Time
Site:	Davis Besse
Issue date:	02/28/2013
From:	Lieb R A FirstEnergy Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-13-098, TAC ME4640
Download: ML13063A033 (5)

Text

FENOCTMFE OC% 5501 North State Route 2FirstEnergy Nuclear Operating Company Oak Harbor, Ohio 43449Raymond A. Lieb 419-321-7676Vice President, Nuclear Fax:419-321-7582February 28, 2013L-1 3-098 10 CFR 54ATTN: Document Control DeskU. S. Nuclear Regulatory CommissionWashington, DC 20555-0001SUBJECT:Davis-Besse Nuclear Power Station, Unit No. 1Docket No. 50-346, License Number NPF-3Revised Reply to Request for Additional Information for the Review of the Davis-BesseNuclear Power Station, Unit No. 1, License Renewal Application (TAC No. ME4640)By letter dated August 27, 2010 (Agencywide Documents Access and ManagementSystem (ADAMS) Accession No. ML102450565), FirstEnergy Nuclear OperatingCompany (FENOC) submitted an application pursuant to Title 10 of the Code ofFederal Regulations, Part 54 for renewal of Operating License NPF-3 for theDavis-Besse Nuclear Power Station, Unit No. 1 (Davis-Besse). By letter L-13-037dated February 12, 2013, FENOC replied to Nuclear Regulatory Commission (NRC)requests for additional information (RAIs) related to NRC review of the Davis-BesseLicense Renewal Application (LRA). During a telephone conference with the NRCProject Manager for Davis-Besse License Renewal held on February 19, 2013, theNRC stated that it appeared there was a typographical error in the FENOC response toRAI B.2.43-2a regarding the value for university testing crack size.FENOC performed a review of the response to RAI B.2.43-2a and confirmed that theuniversity testing crack size of 0.20 inches provided in the response was atypographical error. The correct value for the crack size should have been 0.020 inches.FENOC performed a review of the entire response and identified one additional changein the response. Specifically, in the fourth paragraph of the response, the statement that"[t]wo adjacent splices at 6 inches on center spacing were used" should read "[t]woadjacent splices at clear spacing of approximately 6 inches were used", since thespacing between the splices was not "on center" spacing. These conditions wereentered into the FENOC Corrective Action Program.The Attachment provides the revised FENOC reply to NRC request for additionalinformation B.2.43-2a. The NRC request is shown in bold text followed by the FENOCresponse.1W1(45 Davis-Besse Nuclear Power Station, Unit No. 1L-13-098Page 2There are no regulatory commitments contained in this letter. If there are any questionsor if additional information is required, please contact Mr. Clifford I. Custer, FleetLicense Renewal Project Manager, at 724-682-7139.I declare und r penalty of perjury that the foregoing is true and correct. Executed onFebruary ;,k, 2013.Sincerely,RayýoA L ie bAttachment:Revised Reply to Request for Additional Information for the Review of theDavis-Besse Nuclear Power Station, Unit No. 1 (Davis-Besse), License RenewalApplication (LRA), Section B.2.43cc: NRC DLR Project ManagerNRC Region III Administratorcc: w/o AttachmentNRC DLR DirectorNRR DORL Project ManagerNRC Resident InspectorUtility Radiological Safety Board

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L-1 3-098Revised Reply to Request for Additional Information for the Review of theDavis-Besse Nuclear Power Station, Unit No. 1 (Davis-Besse),License Renewal Application (LRA),Section B.2.43Page 1 of 3Question RAI B.2.43-2aBackground:By letter dated November 20, 2012, the applicant responded to a request foradditional information (RAI) regarding the proposed monitoring methods for theshield building (SB) cracking. The RAI response indicates that the proposedinspection sample size of 20 core bores will cover the three areas of cracking(flute shoulders, upper 20 ft of the building, and the steam line penetrations) andis adequate to identify any changes in the laminar cracking, without furtherimpulse response testing during the period of extended operation.Issue:As part of evaluating the applicant's plan for monitoring the SB cracking withcore bores, the staff needs to understand the technical basis for the size of thesample. For example, is the sample based purely on statistics or is it based onthe long term effect of the concrete cracks on the ability of the reinforcement tocarry design loads and the safety significance of the cracking. In an earlier RAIresponse, dated April 5, 2012, it was indicated that the structural impact of thecracking would be determined via testing. A summary description of the testresults and discussion of how the test results demonstrate that the sample size issufficient has not been provided.Request:Provide a discussion of the technical basis for the adequacy of the sample size. Ifthe sample size was based on laboratory testing, provide a summary of thetesting. Include an explanation of the testing completed as well as the results,and how this information relates to the structural capacity of the SB and supportsthe adequacy of the sample size.Telephone Conference Call Summary:The NRC Staff initiated a telephone conference call with FENOC on January 16,2013, to discuss and clarify NRC follow-up RAIs B.2.43-2a and B.2.43-3a regardingthe Davis-Besse Shield Building Monitoring Program. Following discussions, NRCStaff stated that, instead of addressing RAI B.2.43-2a as written, FENOC shouldrespond to the RAI by providing summaries of the laboratory (i.e., university)testing performed and the results of the testing. The summary should address the

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L-1 3-098Page 2 of 3Shield Building reinforcing bar-concrete bond strength, the assumptions made inthe structural operability calculations regarding bond strength, and how thetesting performed supports those assumptions. A copy of laboratory reports isnot needed by the NRC Staff.RESPONSE RAI B.2.43-2aTesting was performed at the University of Kansas and at Purdue University to assessthe concrete-rebar bond strength of concrete with a laminar crack. Given theconservative nature of the test conditions used in these studies, it is concluded that thereinforcement in the Shield Building experiences little, if any reduction in strength andcapacity due to the laminar cracking condition.During the evaluation of the Shield Building laminar cracking in 2011, FENOC performedcalculations to document that the Shield Building remains capable of performing itssafety functions despite the presence of laminar cracking. FENOC assumed in theevaluation calculations that there was no reinforcement capacity in cracked zones wherethe reinforcing bar included splices. The rationale for the assumption was that unsplicedrebar spanning cracked zones retained capacity, while reinforcement capacity with rebarsplices could not be quantified, and therefore was considered ineffective in the analysis.It was recognized at the time that follow-up laboratory testing was required to confirmassumptions regarding reinforcement capacity of spliced rebar.FENOC sponsored independent testing programs at Purdue University and theUniversity of Kansas to determine the effects of laminar cracking in the plane of andparallel with reinforcing bar splices (a condition similar to the Shield Building laminarcracking). The laboratory testing confirmed that the robust design and construction of theShield Building allow the building to retain significant margin against design loads evenwith laminar cracking.Both universities conducted testing programs to evaluate the effects of the laminarcracking using large scale rectangular section beams with size #11 tensionreinforcement splices. The #11 reinforcement was chosen since it matches the size usedin the construction of the Shield Building. Two adjacent splices at clear spacing ofapproximately 6 inches were used in all beams to simulate rebar interaction. The testspecimen set-up at both universities was conservative since the Shield Buildingreinforcement splices are staggered, and not side-by-side, as constructed at bothlaboratory test facilities. Both testing programs used materials that were representativeof the Shield Building materials with similar strengths. Concrete strengths of the sampleswere representative and conservative relative to the strength of the materials in theShield Building. Select beams in both the Purdue and Kansas studies were subject toreload cycles. These beams were loaded to develop the crack (at calculated yield),unloaded, and the beams were reloaded to failure. The crack sizes developed exceededthe crack widths identified in the Shield Building.

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L-1 3-098Page 3 of 3Purdue University tested six samples with 120-inch splices and six samples with 79-inchsplices. These splice lengths correspond to the splice lengths used in the ShieldBuilding. Purdue used beam geometry in order to produce a preferential (laminar) crackat the location of reinforcement when loaded.During testing, cracks developed and opened to widths exceeding 0.10 inches whenapproaching the maximum load. These crack widths well exceeded the Shield Buildingcracks identified and essentially covered the entire test span prior to failure.Each of the beams tested demonstrated two fundamental properties:1. Each beam developed yielding stress in the reinforcement after thedevelopment of laminar cracks, and2. The load deflection curves for each beam exhibited classic ductile behavior withincreasing deflection beyond the yield point.These tests demonstrate that the reinforcement, and therefore the building as a system,retains its strength despite cracking, given the reinforcement was capable of developingyield stress. By exhibiting ductile behavior, the tests confirm that despite the laminarcracking condition, the building system can be expected to demonstrate the classicallyrequired deflection and surface cracking indications prior to failure.The University of Kansas also used a large-scale rectangular beam section with #11rebar splices as noted above; however, the main study beams were cast with a cold jointin the plane of the reinforcement for a length greater than the entire splice length. TheUniversity of Kansas tested 6 beams: 3 with 79-inch splices, and 3 with 120-inch splices.These splice lengths correspond to the splice lengths used in the Shield Building.For the beams with the reload cycles, crack widths were at or greater than a width of0.020 inches prior to unloading. This exceeds the crack widths identified in the ShieldBuilding by a factor of approximately 2. These specimens developed capacities near andabove yield despite the conservative testing conditions.Given the conservative nature of the conditions used in the tests, it is the conclusion ofthe professors who conducted and evaluated the tests that the reinforcement in theShield Building experiences little, if any, reduction in strength and capacity due to thelaminar cracking condition. The studies also document that the structure retains itsserviceability and ductile behavior. The university test findings provide additionalconfidence in structural adequacy above that already documented in the functionalitycalculations, and confirmed that the robust design and construction of the ShieldBuilding allow the building to retain significant margin against design loads even withlaminar cracking.