L-12-055, Response to Request for Additional Information on 10 CFR 50.46 Report of Changes or Errors in ECCS Evaluation Models

Response to Request for Additional Information on 10 CFR 50.46 Report of Changes or Errors in ECCS Evaluation Models

ML120440609
Person / Time
Site:	Davis Besse
Issue date:	02/13/2012
From:	Allen B S FirstEnergy Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-12-055
Download: ML120440609 (3)

Text

FENOC fl rctEnergy Nuclea Operatlng Conpany 5501 Notth Slata Rwte 2 OakHartuc Ohlo43449 8uty8,Nen Vice President - Nuclear February 13,2412 L-12-055 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

SUBJECT:

Davis-Besse Nuclear Power Station ECesEvaluationW

,*,Xi!"#',-it{f, 10 cFR 50.a6(aX3Xii)Docket No.

50-346, License No. NPF-3 Response to Reouesifor Additional Information on 10 CFR 50.46 Report of Chanoes 9rBy letter dated May 27,2011 (Agencywide_Documents Access and Management system (nOnUS) Accession No. ML1 tl-5fi6q4, FirstEnergy Nuclear Operating Company iff5fOCisubmitted the annual report for changes and errors in an emergency core cooling system {ECCS) evaluation tnoO"f iiMl, ot in the application of such a model' for the Davis-Besse Nuclear power Station. ine report covered the period from January 1,2A10 to December 31, 2010.On January 18, 2012,the Nuclear Regulatory Commission (NRC) requested additional information

,.gurdin;'this report. FEl.iOC't i"tponse to the request, as discussed withNRC staff on December 19, 2011, is attached.

There are no regulatory commitments contained in this letter. lf there are any questions or if additional informrtion is required, please contact Mr. Phil H. Lashley, Supervisor

-Fleet Licensing, at (330) 315-6808.

Sincerely, ,t*,- 5,4e'--1Barry S. Allen

Attachment:

Response to Request for Additional Information on the 10 CFR 50'46 nep{ of Cianges or Errors in the emuigency Core CoJting System Evaluation Model for the Davis-Besse Nuclear Power Statloncc: NRC Region lll Administrator NRC Resident InsPector Nuclear Reactor Regulation Project Manager Utility Radiological Safety Board Attachment L-12-055 Response to Request for Additional Information on the 10 CFR 50.46 Report ofChanges or Errors in the Emergency Core Cooling System Evaluatlon Modelfor the Davis-Besse Nuclear Power Station Page 1 ot2By fetter dated May 27,2011 (Agencyruide Documents Access and Management System (ADAMS) Accession lrto. wtt-i 11510642), FirstEnergy Nuclear Operating Cbmpany (FENOC) submitted the annual report for changes a1d errors in an emergency core cooling system (ECCS) evaluation model (Elr4),-o1.in the application of such a model, for the Dlvis-Besse Nuclear Power Station (DBNPS), On January 18,2i.A12, the Nuclear Regulatory Commission (NRC) requested additional information regarding this report. lne ruRC staff's request is presented in bold type'followed by FENOC's response.ln Table 1, "10 CFR 50.46 Summary for 2010," lt is noted that peak cladding temperatures for Mk.B.HTP fuel Inihe mixed-core and full'core large'break loss'of-coolant accident (LBLOCA) evaluation models are "estlmated" per Evaluation Model Revision 0.9.

Please ciarify why these specific peak cladding temperatures are ,,estimated" and not "analyzed" slmilar to the other values in the table'FENOC began inserting the new Mk-B-HTP fuel assemblV de191into the DBNPSreactor in Cycle 15, which began in April 2006. The original L-BLO.CAenalyses for peak cladding temperature (PCT) f6r the transition cores and the Mk-B-HTP full-core were pefformed prior to cycle ts. nt that time, analyzed LBLOCA PCT values of 2095'3"F lMk-a-Hrp mixed-core) and 2117.2'F (Mr<-g-FifP full-core) were reported to FENOCby the fuel vendor,By letter dated May 25,,2007 (ADAMS Accesslon No, ML071500391), FENOCsubmitted the 2006 annual report of changes to the 10 CFR 50'46 ECCS EM' whichinctuded tho anaryzed LBLocA pcr vatu6 of 209s"F (rou{gd-down from 2095.3"F) forthe Mk-B-HTp mixed-core.

Since a full core of the Mk-B-HTP fuelwould not beachleved until cycle 17 in 2010, a full-core LBLOCA PCT value was not included in the 2006 through 2009 reports.By letter dated May 28, 2008 (ADAMS Accession No. ML081540470), FENOC submitted the 2oai annual report of changes to the 10 cFR 50.46 Eccs EM, including the effect of an EM application error for tG Mk'B-HTP mixed'core results' The error, as explained in the ZilOl report, was an inconect interpretation of gqmTa energyfractions reported from the bnlCeruZ computer code. This was evaluated by the FENOC fuel vendor and was found to cause an increase in the Mk-B-HTP mixed-core pCT value of +Z.TiF,leading to the final 2007 reported value of 2098'F (rnixed'core)

.shown in Table 1 of that letter. However, the value was reported as "analyzed" when, in fact, it was "estimated" by the FENOC fuel vendor, as required by10 CFR 50.46(aX3Xi). ln ttre 2009 report, submitted by letter C.atgd May 27 ' 2010 (ADAMS nccebdibn'No.

ML101530497), the values were reported correctly as"estimated,"

Attachment L-12-055Page 2 of 2In 2010, when the full core of Mk-B-HTP assemblies was achieved, a PCT value for the Mk-B-HPT full-core LBLOCA was included in the annual report, submitted by the May 27,2011 letter. The gamma energy fraction error noted in the 20OT report also affected the Mk-B-HTP full-core LBLOCA PCT value. The magnitude of the errorwas estimated as +1.8oF for the Mk-B-HTP full-core that yielded an estimated PCT of2119"F when added to the 2117 .2'F full-core analyzed value, Subsequently, in theMay 27,2011 letter, FENOC reported the 2119oF estimated value being utilized at thattime rather than the original analyzed value of 2117.2"F.