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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,

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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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