safety evaluation re error in exxon loca-eccs analysis for
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g[ *g UNITED STATESg NUCLEAR REGULATORY COMMISSION
D p WASHINGTON, D. C. 20555
\...../SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
OMAHA PUBLIC POWER DI5TRICT -
DOCKET NO. 50-285FORT CALHOUN UNIT 1 RESPON5ES REGARDING
EXXON CODE ERROR
INTRODUCTION
On March 15, 1985 Exxon Nuclear Corporation infonned the NRC of a
coding error in the T00DEE2 computer code stiich affected the LOCA-ECCS analyses
for several PWRs. In refgrence 1 Exxon provided a description of the codingerror. The error was in an expression for a multiplier on the reflood heat
transfer coefficient. The incorrect coding caused the heat transfer
co'fficient multiplier to be 1.045, when it was intended to be 1.0.e
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In addition to the coding error in the T000EE2 code, the staff has also become
aware of other errors in Exxon LOCA analyses. These include:;
-Use of heat transfer augmentation factors for local rod peaking and
mixing vanes in some recently submitted LOCA analyses perfonned to
support license amendment applications. The use of these factors was
found unacceptable some time ago during our review of the EXEM/pWR ECCS
evaluation model.
-Discovery of an input error in the St. Lucie Unit 1 LOCA analysis. This
error is described in Reference 2.
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-Assuming the validity and applicabilty of applying the Wettinghoute-derived
K(z)curvetoExxonfuel.
0507030229 050613PDR ADOCK 05000205P PDR
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In order to determine the extent to which the staff concerns with respect to
the Exxon LOCA models and analysis methods were generically applicable, the staff_
contacted all PWR licensees using Exxon fuel on March 20, 1985. At that time,
the staff requested that each of the licensees evaluate these concerns with.
respect to their plants and determine if they were applicable.
On March 25, the licensee for Fort Calhoun Unit 1, Omaha Public Power District,
provided in reference 3 their evaluation of the Exxon LOCA issues.
Supplemental information was provided by the licensee in reference 4. The staff's
evaluation of this information follows:
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EVALUATION
The current Exxon LOCA analysis, applicable to Cycle 8 operation of Fort
Calhoun Unit 1, was transmitted to the staff in reference 5. In reference 3,
the licensee stated that they were informed by Exxon that the reference 5
analysis utilized the T00DEE2 code version which had the coding error. The
reference 5 analysis did not utilize the unacceptable augmentation factors nor
did it contain the St. Lucie Unit 1 input error.
The licensee also provided in reference 3 the results of a revised LOCA
analysis using a corrected version of the T00DEE2 code. Via reference 4, the
licensee provided supplemental information describing the ECCS evaluation model
utilized for the revised analysis. The licensee reported that the corrected
evaluation increased the peak cladding temperature from 2052*F to 2104'F.,
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The staff has reviewed the licensee's revised analysis. Based upon the informa-
tion contained in reference 4, the staff has concluded that the evaluation model
utilized fully conforms to Appendix K to 10 CFR 50. Also, the staff has have
also concluded that the licensee is in conformance with 10 CFR 50.46 as the
peak cladding temperature is less than 2200'F.
The remaining Exxon LOCA issue for Fort Calhoun Unit I concerns the validity of,
assuming use of the Westinghouse-derived K(z) curve for Exxon fuel. Since Fort
Calhoun Unit 1 is a Combustion Engineering plant and not a Westinghouse plant,
the direct application of this concern is not possible. However, the intent of
the K(z) curve is the Westinghouse Technical Specifications is to ensure
conformance to 10 CFR 50.46 for a range of power distributions and peaking
factors that may occur over the core lifetime per the requirement of Section
I.A of Appendix K to 10 CFR 50. Thus, the concern for Fort Calhoun Unit 1 is
whether the Exxon LOCA analyses, and the associated plant Technical
Specifications, comply with the requirements of Section I.A of Appendix K.
,In reference 4, the licensee stated that non-uniform axial power distributions
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were used in the Fort Calhoun Unit 1 LOCA analyses perforned by Exxon. These
analyses are discussed in Section 14.15 of the Fort Calhoun Unit 1 FSAR. Based
upon these analyses an allowable total peaking factor versus core height curve.
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was generated. Associated Technical Specifications are employed to-assure this
curve is not e.<ceeded. Based upon this information, the staff has concluded
that the Fort Calhoun Unit 1 LOCA analyses comply with Section I.A of Appendix K.
CONCLUSION
Based upon the foregoing, the staff has concluded that the revised LOCA analyses
for Fort Calhoun fully comply with the requirements of 10 CFR 50.46 and Appendix K.
Principal Contributor:
R. Jones, DSI
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Reference,
1. Letter, G. F. Owsley (ENC) to H. Denton (NRC), " Error in the 48,000MWD /MTU LOCA-ECCS Analysis for D. C. Cook Unit 1," GF0:85:008, March 21,1985.
2. Letter, J. W. Williams, Jr. (FPL) to J. R. Miller (NRC), "St. Lucie Unit 1Docket No. 50-335, ECCS Analysis," L-85-124, March 22, 1985.
3. Letter, R. L. Andrews (Omaha Public Power District) to J. R. Miller (NRC)," Error in LOCA-ECCS Analysis for Fort Calhoun Station," LIC-85-122,March 25, 1985.
4. Letter, R. L. Andrews (Omaha Public Power District) to J. R. Miller (NRC)," Error in LOCA-ECCS Analysis for Fort Calhoun Station," LIC-85-141,
A,
April 14, 1585.'
5. Letter, W. C. Jones (Omaha Public Power District) to R. A. Clark (NRC).LIC-82-410, December 29, 1982.
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Mr. R. L. AndrewsOmaha Public Power District Ft. Calhoun Station, Unit No. 1
Harry H. Voigt Esq.LeBoeuf, Lamb, Leiby A MacRae
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1333 New Hampshire Avenue, NWWashington, DC 20036
Mr. Jack Jensen, ChairmanWashington County Board
of SupervisorsBlair, Nebraska 68023
Metropolitan Planning AgencyATTN: Dagnia Prieditis7000 West Center RoadOmaha, Nebraska 68107
Mr. Larry YandellU.S. NRC Resident InspectorPost Office Box 309Fort Calhoun, Nebraska 68023s
Mr. Charles B. Brinkman, ManagerWashington Nuclear OperationsC-E Power Systems7910 lloodmont AvenueBethesda, Maryland 70814
Regional AdministratorUSNRC, Region IVOffice of Executive Director
for Operations611 Ryan Plaza Drive, Suite 1000Arlington, Texas 76011
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