ML19290E747
| ML19290E747 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 02/25/1980 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Pilant J NEBRASKA PUBLIC POWER DISTRICT |
| References | |
| TAC-12589, NUDOCS 8003140468 | |
| Download: ML19290E747 (3) | |
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jg UNITED STATES 3s, g
NUCLEAR REGULATORY. COMMISSION y
j WASHINGTON D. C. 20555 February 25, 1980 Docket No. 50-298 Mr. J. M. Pflant, Director Licensing & Quality Assurance Nebraska Public Power District Post Office Box 499 Columbus, Nebraska 68601
Dear Mr. Pilant:
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 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 f sm turbine disc inspections now underway at Arkansas Nuclear One Unit 1, Beaver Valley Unit I 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 informa-tion and the actions being taken by the licensee-users, we consider this warrants 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 operation until such inspections are made and all defects thus identified are 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 event prior to restart if your unit is not operating, written statements, signed under oath or affirmation, which will enable the staff to determine whether or not your license to operate the Cooper Nuclear Power Station should be modified, suspended, or revoked. As part of your statement, you should provide and address the safety significance of the information requested in Enclosure 2 to this letter.
8003140 it
. 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 th2 December 17, 1979 meeting we urge you to address the generic aspects of this problem and to coordinate your responses
'brough an owner's group.
- incerely,
~
arrell 6.
i*se hu., Acting Director Division o Operating 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
Mr. J. M. P11 ant Nebraska Public Power District
-3 cc:
Mr. G. D. Watson, General Counsel Nebraska Public Power District P. O. Box 499 Columbus, Nebraska 68601 Mr. Arthur C. Gehr, Attorney Snell & Wilmer 3100 Valley Center Phoenix, Arizona 85073 Cooper Nuclear Station ATTN:
Mr. L. Lessor Station Superintendent P. O. Box 98 Brownville, Nebraska 68321 Auburn Public Library 118 - 15th Street Auburn, Nebraska 68305
UNITED STATES ISINS NO.:
6870 NUCLEAR REGULATORY COMMISSION Accession No.:
OFFICE OF INSPECTION AND ENFORCEMENT 791C250525 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 cf the Office of Inspection and Enforcement, on November 17, 1979 which alleged possible violatien of Part 10 CFR 50.55e and/or 10 CFR 21 Regulations concerning reportability of recently discovered stress corrosion cracking in Westinghouse 1800 rpm icw pressure turbine discs.
Westinghouse had made a presentation on the turbine disc cracking to electric utility executives on October 30, 1979.
Telephone discussions between the NRC staff and Westinghouse's Turbir.e Division on November 20, 1979 established that cracking, attributed to stress corrosion phenomena, 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 examination) for crack detection have bcen develcped and are being imple-mented in the field.
The Office of Inspection and Enforce ent was a'so notified on November 20, 1979 that during the current overhaul of Com onwEalth Edison's Zion Unit 1 LP turbine, ultrasonic examination revealed embedded 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 findir.gs show them not to be typical of classical stress corrosion cracking observed in the keyways.
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, Westirghouse and utility representatives to discuss the disc cracking problem, re: air alter-r.atives, turbine missile evalua.icn, inspection techniques and p' ant ins;:ection priorities.
In response to the staffs' request, Westi.1gnouse pr:vidad the staff an updated report on December 21, 1979 regarding tne curre-t field inspection program that included a list of nuclear power plants already ins:ected, recom-mended inspection schedules and pertinent information rela ed to L? turbines where cracks have been observed.
Inspections to date have identified turbine disc cracks at Surry Unit 2, Point Beach Unit 2, Palisades, Indian Pcint Unit 3 and Zion Unit 1.
All units except Point Beach Unit 2 will make repairs before the plants return to power.
Point with a small crack in the No. 2 dis Westinghouse indicated that the obs during 28 additional conths of turb DUPLICATE. DOCUMENT the turbine inspection results and Entire document previously entered into system under:
ANO No. of pages:
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