ML19305C394
| ML19305C394 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/25/1980 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Dietch R SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 8003280486 | |
| Download: ML19305C394 (5) | |
Text
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og UNITED STATES
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g NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 jg f
February 25, 1980 Docket No. 50-206 Mr. R. Dietch Vice President Nuclear Engineering and Operations Southern California Edison Company 2244 Walnut Grove Avenue Post Office Box 800 Rosemead, California 91770
Dear Mr. Dietch:
On December 28, 1979 the NRC Office of Inspection and Enforcement issued Information Notice No. 79-37 that presented information available to the staff related to the discovery of cracks in the keyway and bore sections of Westinghouse 1800 rpm low pressure turbines.
A copy of this Information Notice with errata sheet is enclosed.
Westinghouse notified utility users of this potential problem on October 30, 1979 and was requested by the staff to present a similar briefing in Bethesda, Maryland on December 17, 1979.
You were contacted on December 14, 1979 and invited to send representatives to the staff briefing and also were requested to advise the staff of the actions being taken in regard
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to this potential problem at your operating nuclear power plant.
' Westinghouse was later requested to meet again with the staff and licensee-users on January 8,1980 to supplement the information provided in the earlier meeting and in interim correspondence with the staff.
On the basis of information provided by Westinghouse and.recent indications from turbine disc inspections now underway at Arkansas Nuclear One Unit 1, Beaver Valley Unit 1 and Indian Point Unit 2, it is evident that the probability of crack formation in these turbine discs is significantly greater than previously assumed by the vendor.
In light of this information and the actions being taken by the licensee-users, we consider this warrants j
your prompt full UT inspection of LP rotor discs, especially the keyways and bore areas, and documentation to the NRC of your justification for continued l
cperation until such inspections are made and all defects thus identified are l
corrected.
Therefore, in accordance with 10 CFR 50.54(f), you are requested to provide within 20 days of the date of this letter, or in any even; prior to restart if your unit is not operating, written statements, signed under cath o-affirmation, which will enable the staff to determine whether or not your license to operate San Onofre Nuclear Generating Station, Unit No.1 should be modifi.ed, suspended, or rev-ked.
As part of your statement, you should provide and address the safety ;ignificance of the information recuested in Enclosure 2 to this letter.
e 8 0 03 280+96
Mr. R. Dietch 2-February 25, 1980 Because of the general nature of the information sought in Enclosure 2 we are transmitting a copy of this enclosure to Westinghouse by separate letter. As discussed in the December 17, 1979 meeting we urge you to address the generic aspects of this problem and to coordinate your responses through an owner's group.
incerely,
l 1,
Darrell G.
- enhut, eting Director Division of erating Reactors
Enclosures:
1.
IE Information Notice No. 79-37 With Errata Sheet 2.
Request for Information Related to Turbine Disc Cracks - 20 Day Response cc:
w/ enclosures See next page 9
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Mr. R. Dietch February 25, 1980 i
cc w/ enclosures:
Charles R. Kocher, Assistant Director, Technical Assessment General Counsel Division Southern California Edison Company Office of Radiation Programs Post Office Box 800 (AW-459)
Rosemead, California 91770 U. S. Environmental Protection Agency David R. Pigott Crystal Mall #2 Samuel B. Casey Arlington, Virginia 20460 Chickering & Gregory Three Embarcadero Center U. S. Environmental Protection Twenty-Third Floor Agency San Francisco, California 94111 Region IX Office ATTN:
EIS C0ORDINATOR Jack E. Thomas 215 Freemont Street Harry B. Stoehr San Francisco, California 94111 San Diego Gas & Electric Company P. C. Box 1831 San Diego, California 92112 Resident Inspector c/o U. S. NRC P. O. Sox 3550 San Onofre, California 92672 Mission Viejo Branch Library 24851 Chrisanta Drive Mission Viejo, California 92676 Mayor
' City of San Clemente San Clemente, California 92672 Chai rnan Board of Supervisors County of San Diego San Diego, California 92101 California Department of Health ATTN: Chief, Environmental l
Radiation Control Unit Radiological Health Section 71 P Street, Roca 498 Sacranento, California 95814
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UNITED STATES ISINS NO.:
6870 NUCLEAR REGULATORY COMMISSION Actession No OFFICE OF INSPECTION AND ENFORCEMENT s ef -* G91 WASHINGTON, D.C.
20555 December 28, 1979 IE Information Notice No. 79-37 CRACKING IN LOW PRESSURE TURBINE DISCS Description of Circumstances:
An anonymous letter was received by the Director of the Office of Inspection and Enforcement, on November 17, 1979 which alleged possible violation of Part 10 CFR 50.55e and/or 10 CFR 21 Regulations concerning reportability of recently discovered
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stress corrosion cracking in Westinghouse 1800 rpm low pressure turbine discs.
Westinghouse had made a presentation on the turbine disc cracking to electric utility executi,ves on October 30, 1979.
Telephone discussions between the NRC staff and Westinghouse's Turbine Division on Novecber 20, 1979 established that cracking, attributed to stress corrosion pheno ena, had been found in the keyway areas of several LP turbine discs at operating plants and that inservice inspection techniques (i.e., in situ ultra-sonic exa-ination) for crack detection have been ceveloped anc are being imple-mented in the field. The Office of Inspection and Enforcement was also notified on November 20, 1979 that during the current overhaul of Commcnwealth Edison's Zion Unit 1 LP turbine, ultrasonic examination revealed embedcec cracks located on the inlet side on the disc bore area where no cracks had been previously observed.
Ultrasonic measurements indicate this disc bore cracking is of greater depth than the keyway cracks found to date.
According to Westinghouse, these -
bore cracks have been metallurgically examined and preliminary findings show them not to be typical of classical stress corrosion cracking observed in the keyways.
l The probable cracking mechanism and impact on disc integrity is being further evaluated, by Westinghouse.
A meeting was held on December 17, 1979 between the NRC staff, Westinghouse and utilicy representatives to discuss the disc cracking proble, repair alter-natives, turbine issile evaluation, inspection te:hniques anc plant inspection priorities.
In response to the staffs' request, bestinghouse proviced the staff an updated report on December.21,1979 regarding the current field inspection that included a list of nuclear power plants already inspected, recom-progra menced inspection scheduies and pertinent information related to LP turbines 1
where cracks nave been cbserved.
Inspections to cate have identified turbine l
disc cracks at Surry Unit 2, Point Beach Unit 2, Palisades, Indian Point Unit 3 i
and Zion Unit 1.
All units except Point Beach Unit 2 will make repairs before tne plants return to power.
Point Beech returned to power on December 23, 1979 with a s=all crack in the No. 2 disc of LP Turbine No. 2.
An analysis by Westinghouse indicated that the observed crack will not attain critical dimensions during 28 additional conths of turbine operation. The NRC staff is evaluating the turbine inspection results and analysis by Westinghouse.
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