ML19305B097
| ML19305B097 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/25/1980 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Lundvall A BALTIMORE GAS & ELECTRIC CO. |
| References | |
| IEIN-79-37, NUDOCS 8003190148 | |
| Download: ML19305B097 (3) | |
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[an af og'o UNITED STATES 8
NUCLEAR REGULATORY COMMISSION o
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,, l WAsmGTON, D. C. 20666 o
February 25, 1930 Docket No. 50-318 Mr. A. E. Lundvall, Jr.
Vice President - Supply Baltimore Gas & Electric Cenpany P. O. Box 1475 Baltimore, Maryland 21203
Dear Mr. Lundvall:
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 Infor-mation 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 probler at your operating nuclear power plant.
Westinghouse was
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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 proba-bility 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 bo.re areas, and documentation to the NRC of your justification fur continued operation until such inspections are made and all defects thus identified are i
l corrected.
Therefore, in accordance with 10 CFR 50.54(f), you are requested l
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 state ents, signed under oath or affimation, which will enable the staff to determine whether or not l
your license to cperate Calvert Cliffs Unit No. 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.
8003190148
Mr. A. E. Lundvall, Jr. Because of the gene-al nature of the information sought in Enclosure 2 we are transn:itti,
ccpy 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 throug1 an owner's group.
incerely.
L l
&nhu.,
ng irector a e u.
Division of perating Reactors
Enclosures:
1.
IE Inforraticn Nc-ice No. 79-37 With Errata Sheet 2.
Request for Infor ation Related to Turbine Disc Cracks - 20 Day Response cc:
w/ enclosures-See next pase r m v.
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. ialtihcre Gas & Electric Company
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cc:
- a..es A. Biddison, Jr.
Mr. R.
P.. Douglass, Manager
~ General Counsel Quality Assurance Departmen-3 ar.d E Builcin; Room 923 Gas F, Electric Building i_
Charles Center P. O. Box 1475
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Saltimore, Maryland 21203 Baltirore, P.aryland 21203 E.;
dM"t George F. Trowbridge, Esquire g;.
Shaw, Pittnan, Potts and g.:. _.
Trowbridge g.:.
1800 M Street, P "
i'ashington, D. C.
20036
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!!r. R. C. L. Olson 3altinore Gas and Electric Company Room 922 - G ar.d E Building
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Post Office Box 1476
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Saltinore, Maryland 21203
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fir. Leon B. Russell, Chief Engineer Calvert Cliffs !!uclear Power Plant
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Baltinore Gas and Electric Company
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Lusoy, !!arylanc 20657 n;
5e:htel Power Corporation ATit!:
fir. J. C. Judd Chief Nc: lear Engineer 15740 Shady Gr:ve F.oad Gaitnersburg, furyland 20760
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Ocabustion Engineering, Inc.
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!!r. P.
k'. Kruse, !!anager Engineering Services Pest Office Box 500
'fi nesor, Connectict.t 06095 y
Calvert County Library Prir.:e Frecerick,liaryland 20678 h
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UNITED STATES ISINS NO.:
6870 NUCLEAR REGULATORY'C0!NISSIOW Accessicn N2.:
OFFICE OF INSPECTION AND ENFORCEMENT 7910250525 VASHINGTON, D.C.
20555 December 28, 1979 IE Information Notice No. 79-37 CRACKING IN LOW PRESSURE TURBINE DISCS Description of Circumstances:
An anonycous 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 stress corrosion cracking in Westinghouse 1800 rpm low 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 Turbine Division on N:. ember 20, 1979 established that cracking, attributed to stress corrosion phen =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 examination) f or crack detection have been developed and are being imple-cented in the field.
The Office of Inspection and Enforcement was also notified on !&.er.ter 20, 1979 that during the current overhaul of Commonwealth Edison's Zicn Unit 1 LP turbine, ultrasenic examination revealed embedded cracks located on tre inlet side on the disc bore area where no cracks had been previously obs e rved.
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 netallurgically examined and preliminary findings show them not to be typical of classical stress corrosion cracking observed in the keyways.
The probable cracking mechani e and impact on disc integrity is being further evalcated by Westinghouse.
A meeting was held on Dececaer 17, 1979 between the NRC staff, Westinghouse and utility representatives to discuss the disc cracking prcblem, repair alter-natives, turbine cissile evaluation, inspection techniques and plant inspection priorities.
In response te the staffs' request, Westinghouse provided 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:
mended inspection schedules and pertinent information related to LP turbines where cracks have been observed.
Inspections to date have identified turbine disc cracks at Surry Unit 2, Point Beach Unit 2, Palisades, Indian Point Unit 3 and Zion Unit 1.
All units except Point Beach Unit 2 will cake repairs before the plants return to peser.
Point Beach returned to power on December 23, 1979 with a scall crack in the No. 2 disc of LP Turbine No. 2.
An analysis by Vestinghouse indicated that the observed crack will not attain critical dimensions during 28 additional conths of turbine operation.
The NRC staff is evaluating
%e turbine inspection results and analysis by Westinghouse.
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'D;c;mber 28,1979 IE Informatien Notice No. 79-37 Page 2 of 2 Westinghouse also notified the stuff that extrapolation of information obtained from Indian Point Unit 3 inspection and analy-is indicates that disc cracking could be significant at Indian Point Unit 2 and the turbines should be inspected
, sooner than the spring outage of 1980.
The NRC staff is currently reviewing 3 Consolidated Edison's plans for prompt evaluation of this potential problem at this unit.
, lists the PWR plants having Westinghouse 1500/1800 rpm turbines.
The AA category represents those turbines which appear to have the earliest need for inspection. With the exception of Yankee Rowe, Westinghouse has recorrended to utilities that inspection of these machines be completed by the Spring 1980 outage period.
The Rowe unit is uninspectable by the present ultrasonic techniques due to its design.
Westinghouse has recommended the remaining machines of the Category A plants be inspected as their service periods approach five years or in the event significant corrosion problems become evident during this time.
The NRC staff is currently reviewing the need for inspection of those PWR plants having other interfacing turbine designs shown in En:losure 2.
Changes to the forementioned inspection schedules proposed by Westinghouse may be necessary as new technical information becomes available.
Frcm the information available to the NRC ' staff at this ti.e it appears that cracking may be more generically widespread in turbine discs (e.g., keyways and bere areas) than previously ot; served.
It is important to note that the UT inspections perfcrmed by Westinghouse thus far were essentially limited to the keyways (disc outlet) of selected discs whereas the Zion Unit 1 inspection results indicate that examination of the disc bore section must be taken into account.
Also, Vestinghouse is currently re evaluating their previously estimated turbine missile energies based on recent missile test results from model symmetric and non-symmetric missile impact tests.
Their preliminary findings, although subject to change, now indicate possible higher missile exit energies in some cases than previously expected.
This Information Notice is provided as an early notification of a possibly sig.ificant matter, the allegations and the generic safety implications of which a e c.:rrently undergoing review by the NRC staf f.
It is expected that recipients will review the information applicable to their facilities.
If NRC evaluations so ir.dicate, further licensee actions may be requested or required.
Embedded cracking in keyways and disc bore areas have been observed only in West'inghouse LP turbines thus far.
However, the NRC staff believes that turbines of other i
manufacturers should be included in consideration of this problem.
t No written response to this Information Notice is required.
If you have any l
questions regarding this matter, please contact the Director of the appropriate l
NRC Regional Office.
Enclosures:
As stated pg @@
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Encicsurb 1
-CATEGORY AA UTILITY STATION UNIT Florida, P&L Turkey Point 3
Consolidated ED.
Indian Point 2
PASNY Indian Point '
3 Arkansas P&L Russellville 1
VEPCO Surry 1
Carolina P&L Robinson 2
So. Calif. Ed.
San Onofre 1
Yankee A.P.
Rowe 1
Wisc. Mich. Pwr.
Point Beach 1
Consumers Pvr.
Palisades 1
Comonwealth Ed.
Zion 1 1
Con.ronwealth Ed.
Zion 2 2
Florida P&L Turkey Point 4
Nebraska PPD Cooper 1
Wisc. Mich. Pwr.
Point Beach 2
Maine Yankee Bailey Point l'
Rochester G&E Ginna 1
Northern States Prairie Island 1
Wisc. P.S.
Kewaunee 1
4.
1 D
Paga 2 of 3 (Continued)
CATEGORY A UTILITY STATION UNIT Alabama Power Farley 1
Alabama Power Farley 2
Baltimore G&L Calvert Cliffs 2
Carolina P&L Harris 1
Carolina P&L Harris 2
Carolina P&L Harris 3
Carolina P&L Harris 4
Cincinnati G&E Zimmer 1
Co~aonwealth Ed.
Byron 1
Comonwealth Ed.
Byron 2
Cocoonwealth Ed.
Braidwood 1
Co.monwealth Ed.
Braidwood 2
Connecticut Yankee Haddam~ Neck 1
Duke Pcwer McGuire 1
Duke Power McGuire 2
Duquesne Lt.
Shippingport 1
Duquesne Lt.
Beaver Valley 1
Duquesne Lt.
Beaver Valley 2
Flordia Power Corp.
Crystal River 3
Flordia Power & Lt.
St. Lucie 1
Flordia Pcwer & Lt.
St. Lucie 2
Houston L&P So. Texas 1
Houston L&P So. Texas 2
Louisiana P&L Waterford 3
Metropolitan Ed.
Three Mile Island 2
Northern States Pwr.
Prairie Island 2
Pub. Service E&G Salem 1
Pub. Service E&G Salem 2
Pacific G&E Diablo Canyon 1
Pacific G&E Diablo Canyon 2
... O W. --
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Enc 1:sure 1 (Continued)
P ge 3 c.f 3 bTEGORYA UTILITY STATION UWIT P.S. Indiana Marble Hill 1
P.S. Indiana Marble Hill 2
Puget Sound P&L Skagit 1
SHUD.
Rancho Seco 1
TVA Sequoyah 1
TVA Sequoyah 2
TVA Watts Bar 1
TVA Watts Bar 2
VEPCO North Anna 1
VEPCO North Anna 2
VEPCO North Anna 3
VEPCO North Anna 4
VEPCO North Anna 2
WPPSS Hanford 2
WPPSS WNPS 1
WPP55 WNPS 3
WPPSS WNPS 4
WPPSS WNPS 5
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Enclosu're 2 UTILITY STATION UNIT Duke P.ser Co.
Oconee 1
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Duke Power Co.
Oconee 2
Duke Power Co.
Oconee 3
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OPPD Ft. Calhoun 1
Baltimore Electric
& Gas Calvert Cliffs 1
Metropolitan Edison Three Mile Island 1
Indiana & Michigan Electric D.C. Cook 1
Indiana & Michigan Electric D.C. Cook 2
Northcast Utilities Millstone 2
Portland General Electric Trojan 1
Toledo Edisen Davis Besse 1
Arkansas Po-er &
Light Arkansas Nuclear One 2
VPPSS Hanford 1
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Errata Sheet For IE Ir.fo:v.ation Notice No. 79-3L i
Page 1, paragrap 2, line 9:
Change " inlet" to " outlet" Page 1, paragra$ 3, lines 9 and 10: Change " Point Beach Unit 2" to *
" Point Beach Urit 1" Page 1, paragra$ 3, line 10: Af ter Point Beach. Unit 1 add ar. asterisk
("*") footnote and place a note at the bottom of the page as follows:
"* Wisconsin Electric Power Cocpany orally notified the NRC project manager on Nivenber 5 t".at turbine disc cracking had been observed at Point Beach init 1.", lim 4:
Chance "Russellville" to "AN0", lim 8:
Chance to read:
" Yankee Atomic Electric, Yankee Rowe", lines 9 ard 15:
Change "Wisc Mich Pwr" to "Wisc Elec Pwr", line 16: Char.;e to read " Maine Yankee Atomic Pwr, Maine Yankee", page 3, line 13:
Delete as redundant reference to North Anna 2 9
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" Enclosure 2 REQUEST FOR INFORMATION,RELATED TO TURBIriE DISCS SITE SPECIFIC GEt!ERAL QUEST 13t!S - To Be Completed in 20 Days 1.
Provide the following infomation for each LP turbine:
A.
Turbine type B.
Number of hours of operation for each LP turbine at time of last turbine inspection or if not inspected, postulated to turbine inspection C.
Number of turbine trips and overspeeds D.
For each disc:
1.
type of caterial including material specifications 2.
tensile properties data 3.
toughness properties data including Fracture Appearance Transition Temperature and upper energy and temperature 4.
keyway temperatures 5.
calculated key.ay crack size for turbine time specified in "B" above 6.
critical crack size 7.
ratio cf calculated crack to critical crack size 8.
crack grow'h rate 9.
calculated bore and keyway stress at operating design overspeed
- 10. calculated K c data 1
- 11. re.iniau yield strength specified for each disc 11.
Provide details of the results of any completed inservice inspection of LP turbine rotors, including areas examined, since issuance of an operating license.
Fcr each ir.dication detected, provide details of the location of the crack, its orier.ta: ion, and size.
III. Provide the no,ir.al water chemistry conditions for each LP turbine and describe any ccndenser ir. leakages or other significant changes in secondary water chemistry tc this point in its operating life. Discuss the occurrence of cracks in any given turbine as related to history of secondary water chemistry in the unit.
XV.
If your plar.t has not beer. inspected, describe your proposed schedule and approach tc ensure tha turbine cracking does not exist in your turbine.
V.
If your plar.t has been inspected and plans to return or has returned to power with cracks, provice y:ar proposed schedule for the next turbine inspection and the basis for this ir.s;ection schedule.
VI.
Indicate whether ar. analysis and evaluation regarding turbine missiles have been performed for your plant and provided to the staff.
If such an analysis and evaluation has been performed and reported, please provide appropriate references to the available documentation.
In the event that such studies have not been cade, consideration should be given to scheduling such an action.
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2-ENIEIC OUESTIONS - To Be Cocolr.ted in 20 Days Describe what quality control and inspection proce:ures are used for the disc bore and keyway areas.
II.
Provide details of the Westinghouse repair /replacenent procedures for the faulty discs.
III. What icraediate and long tem actions are being taken by Westinghouse to minimize future stress corrosion problems with turbine discs? What actions are being recomended to utilities to nininize stress corrosion cracking of discs?
IT.
Identify the icpurities known to cause cracking in the low pressure turbines, and their sources.
Discuss the relationship between steam generator chemistry and steam chemistry relative t: the introduction of corrosive itpurities into the turbine, inclucin; phosphate, AYT, ZST, and BWR chemistry. Discuss the mechanist of ceposition of these it: purities that car lead to their concentraticn in certain areas of keyways, and bores.
V.
What role does the refluxing action in the stea= separation portion of tre steam generator have on scrubbing corrosive ircuritiet froo the steam?
VI.
To what extent can the buildup of corrosive impurities in the LP turoine be alleviatec? What would be the effects of the following actions:
1.
Pumping moisture separator condensate to condenser?
2.
Periodically acving point of concer.sation te p event localizec buildup of terrosive impurities?
VII.
Describe fabricatic9 and heat treatment sequence for discs, includino
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themal exposure during shrinking operations.
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VIII.
Discuss the effects of any local residual stresses on the cracking mechanism.
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