ML20214M695

Provides Summary of Evaluation Based on 870512,18 & 21 Ltrs Which Provided Specific Details of 870424 Facility Pressurizer Heater Sleeve Leakage.Concludes That Personnel Acted in Responsible Manner by Performing General Walkdown

ML20214M695
Person / Time
Site:	Arkansas Nuclear
Issue date:	05/22/1987
From:	Calvo J Office of Nuclear Reactor Regulation
To:	Tison Campbell ARKANSAS POWER & LIGHT CO.
References
NUDOCS 8706010404
Download: ML20214M695 (3)

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Docket No. 50-368 May 22,1987 Mr. T. Gene Campbell Vice President, Nuclear Operations Arkansas Power and Light Company P. O. Box 551 Little Rock, Arkansas 72203

SUBJECT:

ANO-2 PRESSURIZER HEATER SLEEVE REPAIR By letters dated May 12, 18 and May 21, 1987, you provided specific details of the ANO-2 pressurizer heater sleeve leakage which was discovered on April 24, 1987 and included the results of your subsequent investigations, a description of the proposed repair and an analysis associated with the repair.

The purpose of this letter is to provide a summary of our evaluation based on your submittals described above.

We conclude that your personnel acted in a responsible manner by performing a general walkdown of the reactor coolant system while they were in containment to assess the potential of a small leak on one of the Safety Injection Tanks as indicated by a higher than normal make-up rate to the tank.

During the walk-down, leakage in the area of the pressurizer was detected and additional containment entries confirmed leakage from a pressurizer heater sleeve (approx-imately 0.002 GPM) requiring the shutdown the unit on April 24, 1987 in accordance with the Technical Specifications.

SubsequeatinvestigatIons revealed that two sleeves had degraded. The root cause of the sleeve degra-dations is related to two Watlow heaters which had ruptured.

In 1982, twenty-three out of the ninety-six pressurizer heaters were replaced with the unannealed Inconel 600 Watlow design. The original heaters are of the General Electric design.

All twenty-three unannealed Watlow heaters were removed or replaced with the General Electric heaters.

Regarding the two degraded sleeves, they were removed and temporary plugs were inserted and welded in accordance with the Winter 1985 Addenda of the 1983 Edition of Section III of the ASME Boiler and Pressurizer Vessel Code. We approved your use of this code as an alternative to the one referenced in the regulations by letter dated May 22, 1987.

We have reviewed the design of the plug and determined that the plugs meet all requirements of Section III of the ASME Code with significant margins (i.e.,

the repair weld is larger than that necessary for compliance with Section III).

We also reviewed the adequacy of the weld repair with respect to the potential for hydrogen embrittlement failure and the potential for stress corrosion cracking.

Regarding the potential for hydrogen embrittlement failure, we g 60 % $ $

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. May 22,1987 reviewed-the data provided in your May 21 submittal.

These data predict that the total hydrogen at the wetted surface of the weld is an order of magnitude less than the critical hydrogen level for hydrogen cracking.

Regarding the potential for stress corrosion cracking, we have concluded that the size of the

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weld is considerably larger than required by the code and provides additional-margins. This ensures that a very large crack would have to form in the weld to cause a complete failure, thus greatly improving the probability that a detectable leak would precede complete weld failure. -

We also reviewed the compensatory measures that would be in place until a permanent repair is effected.

They include a monthly tour of the containment for the specific purpose of leak detection and assessment, the rerouting of the suction line of the Containment Atmosphere Monitor to the area immediately above the pressurizer, and refresher training for the operators on the emergency operating procedures associated with a small break LOCA.

Additionally, our regional inspectors reviewed the repair procedure, the training and qualification associated with the repair, and observed certain portions of the actual repair process.

Based on these reviews and observations, we conclude that the repair has been performed in accordance with the applicable code requirements.

We also reviewed the event associated with a complete failure of the weld including plug ejection and missile generation and conclude that the event is bounded by the previously approved accident analysis.

Finally, we conclude that adequate assurance has been provided as to the adequacy of the repair to the pressurizer based on the above considerations.

Our safety evaluation will be provided with a separate letter.

Sincerely, orignalsignedbd Jose A. Calvo, Director Project Directorate - IV Division of Reactor Projects -.III, IV, V and Special Projects cc:

See next page DISTRIBUTION Docket File NRC PDR Local PDR PD4 Reading D. Crutchfield F. Schroeder P. Noonan R. S. Lee J. A. Calvo OGC-Bethesda E. Jordan J. Partlow ACRS (10)

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May 231987 Mr. T. Gene Campbell Arkansas Nuclear One Arkansas Power & Light Company Unit No. 2 cc:

Mr. J. Ted Enos, Manager Mr. Charlie B. Brinkman, Manager Nuclear Engineering and Licensing Washington Nuclear Operations Arkansas Power and Light Company C-E Power Systems P. O. Box 551 7910 Woodmont Avenue Little Rock, Arkansas 72203 Suite 1310 Bethesda, Maryland 20814 Mr. James M. Levine, Director Ca Site Nuclear Operations h,G d

Nuclear Arkansas Nuclear One Operations P. O. Box 608 Arkansas Power and Light' Company Russellville, Arkansas 72801 P. O. Box 551 Little Rock, Arkansas 72203 Nicholas S. Reynolds, Esq.

Bishop, Liberman, Cook, Purcell & Reynolds 1200 Seventeenth Street, N.W.

Suite 700 Washington, D.C.

20036 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Office of Executive Director for Operations 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 Senior Resident Inspector U.S. Nuclear Regulatory Commission P. O. Box 2090 Russellville, Arkansas 72801 Mr. Frank Wilson, Director Division of Environmental Health Protection Arkansas Department of Health 4815 West Markam Street Little Rock, Arkansas 72201 Mr. Robert B. Borsus Babcock & Wilcox Nuclear Power Generation Division Suite 220 7910 Woodmont Avenue Bethesda, Maryland 20814

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