ML19290E753
| ML19290E753 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 02/25/1980 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Mayer L NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 8003140478 | |
| Download: ML19290E753 (3) | |
Text
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'o, UNITED STATES
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NUCLEAR REGULATORY' COMMISSION g \\
E WASHINGTON D. C. 20555 9.,'?v ],)
s, February 25, 1980 Docket Nos. 50-282 and 50-306 Mr. L. 0. Mayer, Manager Nuclear Support Services Northern States Power Company 414 Nicollet Mall - 8th Floor Minneapolis, Minnesota 55401
Dear Mr. Mayer:
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 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 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 evant prior to restart if your units are not operating, written statements, signed under oath or affirmation, which will enable the staff to determine whether or not your license to operate Prairie Island, Unit Nos. I and 2 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
Mr. L. 0. Mayer 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.
S ncerely, y/
[
Darrell G.
isenhut, Acting Director Division of 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. L. O. Fay =r No-the n 5:!:es Power Company February 25, 1980 cc:
Geral: C.narnoff, Esquire Stav, sittr.an, Potts and Trowbridge lEOC F Street, N.W.
Washin; ton, D. C.
20036 Ms. Te ry Hoffman E;ecu:f ve Jirector Minnesota Pollution Control Agency 1535 ',. Coun y Road 82 Resev':1 e, Minnesota 55113 Tre E.*if renmental Conservation Library
"'nnez:clis Public Library 3:0 N":cile: Mall M'nnet:clis, Minnesota 55401 M. F. F. Tierney, Plant Manager Pra'r"a :s and Nuclear Generating Plant N:rthi-r S:a es Power Cor:any R:ute 2 helen. Mir. esota 55089 J:c y-F. Ol sen, Escuire 5:eciC Assistant Attorney General
"'n-en a 3c11ution Control Agency 1535.. Ocurty Road S2 R:sev"? ! e, l'innesota 55113 P::=r-L. Nytc, Jr., Chairman v'r. er::a-W'i sconsin Ecundary Area Carri s sicr.
6:9 Seccnc S:reet E.d sc, n'isconsin 54016 C:a e ce E. rierabend U. 3. N_ clear Regulatory Ccmmission F. T. 3:x 374 Red k ng, v.i nnesota 55066
r.. 1]sure 1 UNIll.0 S TALES ISINS NO.:
6870 NUCI FAR N GUl/ DORY COMISSION Accession No.:
OfH CE OF INSPECTION AND ENFORCEMENT 7910250525 UASHINGTON, D.C.
20555 Decc ber 28, 1979 IE Information Notice No. 79-37 C '.CKING IN 1.0'd PRESSURE TURBINE DISCS Incription of Circumstances:
'n anony.:os letter was received by the Director of the Office of Inspection and Ofurccrent, on November 17, 1979 which alleged possible violation of Part 10 CFR 50.55e and/or 10 CFR 21 Regulations concerning reportability of rec ^ntly discovered tress corrosion cracking in Westinghouse 3S00 rpa low pressure turbine discs.
Vestinghouse had nade a presentation on the turbine disc cracking to electric utility executives on October 30, 1979.
Telephone discussions between the NRC staff and Westinghouse's Turbine Division on November 20, 1979 established that cracking, attributed to stress corrosion
,:henc cna, h-d boen fcund in the tcyaay areas of several LP turbine discs at cperating plints and that inservice inspaction techniques (i.e., in situ ultra-Sonic o,in etion) for cr4ck detection have been eveloped and are being i:ple-d
- nted in t',a field.
The Of fice of In-pe.. tion and Enforcement was also notified on Nc.c 'Ar /0, 19/9 tSat during 'he cori ent uver'ivl of Cor:cr. wealth Edison's lion l'oit 1 LP turbine, ultrs.tenic exc..ination t evcaled embedded cracks located on the ' O t.ida cn the disc hare area here no tracks had bcen previcusly c5scrad.
Ultre u lic r.cssure. ents indicate this disc bore cracking is of greater depth t' sn t he i.ey.,ay cracks found to date.
A.:cor ding to Ue. tinghcuse, these bare cracks hue Lecn ratillurgically examined and preliminary findings show them not to be typical of classical stress corrosion cracking cbserved in the keyways.
The prot 3ble cr.:cking. 2chinis n and impact on disc integrity is beinj further e.aluated by Westinghcuse.
A meeting was held on December 17, 1979 between the NRC staff, Westinghouse and utility representatives to discuss the disc cracking problem, repair alter-ratives, tui bine cissile evaluation, inspection techniques and plant inspection priorities.
In respanca to the staffs' request, Westinghouse provided the st af f an updated r port on Dececber 21, 1979 regarding the current field inspection pi ogram that included a list of nuclear power plants already inspected, recom-mnded irspection schedules and pertinent information related to LP turbines
. Sere cracks have been cbserved.
Inspections to date have identified turbine disc cracks at Surry L' nit 2, Toint Scach Unit 2, Palisades, Indian Point Unit 3 A Zica Unit 1.
All units except Point Ecach Unit 2 will make repairs before
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tha plants retu-n to pc-er.
Toint Be- '
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with a sr.all crack in the No. 2 disc Westinghcuse indicated that the cbse during ?S additional conths of turbir DUPLICATE DOCUMENT e..a turbine inspect)ca results and a.
Entire document previously entered into system under:
ANO 7, -. 3_ 5 d,f N-No. of pages:
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