Information Notice 1979-37, Cracking in Low Pressure Turbine Discs

Cracking in Low Pressure Turbine Discs

ML031180211
Person / Time
Site:	05000000
Issue date:	12/28/1979
From:	NRC/OI
To:
References
IN-79-037, NUDOCS 7910250525
Download: ML031180211 (7)

- fi

UNITED STATES ISINS NO.: 6870

NUCLEAR REGULATORY COMMISSION Accession No.:

OFFICE OF INSPECTION AND ENFORCEMENT 7910250525 WASHINGTON, D.C. 20555 December 28, 1979 IE Information Notice No. 79-37 CRACKING IN LOW PRESSURE TURBINE DISCS

Description of Circumstances

and

An anonvmous letter was received by the Director of the Office of Inspection of Part 10 CFR

Enforcement, on November 17, 1979 which alleged possible violation

reportability of recently discovered

50.55e and/or 10 CFR 21 Requlations concerning discs.

stress corrosion cracking in Westinghouse 1800 rpm low pressure turbine to electric

Westinghouse had made a presentation on the turbine disc cracking

utility executives on October 30, 1979.

Division

Telephone discussions between the NRC staff and Westinohouse's Turbinecorrosion

on November 20, 1979 established that crackinq, attributed to stress

discs at

phenomena, had been found in the keyway areas of several LP turbine situ ultra- in

operating plants and that inservice inspection techniques (i.e.,are beinq imple- sonic examination) for crack detection have been developed and was also notified

mented in the field. The Office of Inspection and Enforcement Edison's

on November 20, 1979 that during the current overhaul of Commonwealth cracks located

embedded

Zion Unit 1 LP turbine, ultrasonic examination revealed had been previously

on the inlet side on the disc bore area where no cracks

is of qreater

observed. Ultrasonic measurements indicate this disc bore cracking these

depth than the keyway cracks found to date. According to Westinqhouse, and preliminary findinqs show them

bore cracks have been metallurgically examined in the keyways.

not to be typical of classical stress corrosion cracking observed

being further

The probable cracking mechanism and impact on disc integrity is

evaluated by Westinghouse.

Westinghouse

A meetino was held on December 17, 1979 between the NRC staff, repair alter- and utility representatives to discuss the disc cracking problem, plant inspection

natives, turbine missile evaluation, inspection techniques and provided the

priorities. In response to the staffs' request, Westinghouse

field inspection

staff an updated report on December 21, 1979 regarding the current inspected, recom- oroaram that included a list of nuclear power plants already to LP turbines

mended inspection schedules and pertinent information related turbine

where cracks have been observed. Inspections to date have identified Indian Point Unit 3 disc cracks at Surry Unit 2, Point Beach Unit 2, Palisades, make repairs before

and Zion Unit 1. All units except Point Beach Unit 2 will on December 23, 1979 the plants return to power. Point Beach returned to power analysis by

with a small crack in the No. 2 disc of LP Turbine No. 2. An critical dimensions

Westinghouse indicated that the observed crack will not attain

is evaluating

durinq 28 additional months of turbine operation. The NRC staff

the turbine inspection results and analysis by Westinahouse.

IE Information Notice No. 79-37 December 28, 1979 Pace 2 of 2 Westinqhouse also notified the staff that extrapolation of information obtained

from Indian Point Unit 3 inspection and analysis indicates that disc crackina

could be significant at Indian Point Unit 2 and the turbines should be inspected

sooner than the spring outace of 1980. The NRC staff is currently reviewing

Consolidated Edison's plans for prompt evaluation of this potential problem

at this unit.

Enclosure 1 lists the PWR plants having Westinghouse 1500/1800 rpm turbines.

The AA cateaory represents those turbines which appear to have the earliest

need for inspection. With the exception of Yankee Rowe, Westinghouse has

recommended to utilities that Inspection of these machines be comDleted 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 Cateqory A plants be inspected as their service

periods aooroach 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 desions shown

in Enclosure 2. Changes to the forementioned inspection schedules proposed by

Westinghouse may be necessary as new technical information becomes available.

From the information available to the NRC staff at this time it appears that

crackinq may be more generically widespread in turbine discs (e.g., keyways and

bore areas) than previously observed. It is important to note that the UT

inspections performed by Westinahouse 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, Westinghouse 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 findinas, although

subject to chance, 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

sianificant matter, the allegations and the generic safety implications of which

are currently undergoing review by the NRC staff. It is expected that recipients

will review the information applicable to their facilities. If NRC evaluations

so indicate, further licensee actions may be requested or required. Embedded

crackino in keyways and disc bore areas have been observed only in Westinghouse

LP turbines thus far. However, the NRC staff. believes that turbines of other

manufacturers should be included in consideration of this problem.

No written response to this Information Notice is required. If you have any

questions recardinn this matter, please contact the Director of the appropriate

NRC Regional Office.

Enclosures: As stated

Enclosure 1 CATEGORY AA

UTIL ITY STATION UNIT

Florida, P&L Turkey Point 3

Consolidated ED. Indian Point 2

PASNY Indian Point 3 Arkansas P&L Russeliville 1

VEPCO Surry 1

Carolina PPbL Robinson 2

So. Calif. Ed. San Onofre 1

Yankee A.P. Rowe 1

Wisc. Mich. Pwr. Point Beach 1

Consumers Pwr. Palisades 1

Commonwealth Ed. Zion 1 1

Commonwealth Ed. Zion 2 2 Florida P&L Turkey Point 4

Nebraska PPD Cooper 1

Wisc. Mich. Pwr. Point Beach 2

Maine Yankee Bailey Point 1

Rochester G&E Ginna 1

Northern States Prairie Island 1

Wisc. P.S. Kewaunee 1

Enclosure 1 (Continued) CATEGORY A

UTILITY STATION UNIT

Alabama Power Fa rley 1

Alabama Power Farl ey 2

Baltimore G&L Calvert Cliffs 2

1 Carolina P&L Harris

Carolina P&L Harris 2 Carolina P&L Harris 3 Carolina P&L Harris 4 Cincinnati G&E Zimmer 1 Commonwealth Ed. Byron 1 Commonwealth Ed. Byron 2 Commonwealth Ed. Braidwood 1 Commonwealth Ed. Braidwood 2 Haddam Neck

1 Connecticut Yankee

1 Duke Power McGuire

McGui re 2 Duke Power

Shippinqport

1 Duquesne Lt. 1 Duquesne Lt. Beaver Valley 2 Duquesne Lt. Beaver Valley

3 Flordia Power Coro. Crystal River

1 Flordia Power & Lt. St. Lucie

St. Lucie 2 Flordia Power & Lt.

1 Houston L&P So. Texas

So. Texas 2 Houston L&P

3 Louisiana P&L Waterford

2 Metropolitan Ed. Three Mile Island

2 Northern States Pwr. Prairie Island

1 Pub. Service E&G Salem 2 Pub. Service E&G Salem

1 Pacific G&E Diablo Canyon 2 Pacific i&E Diablo Canvon

Enclosure 1 (Continued) CATEGORY A

UTILITY STATION UNIT

P.S. Indiana Marble Hill

P.S. Indiana Marble Hill 2

Puget Sound P&L Skaqit 1

SMUD. 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 North Anna 4

VEPCO 2

VEPCO North Anna

WPPSS Hanford 2

WPPSS WNPS 1

WPPSS WNPS 3

WNPS 4

WPPSS 5

WPPSS WNPS

Enclosure 2

UTILITY STATION UNIT

Duke Power Co. Oconee 1

Duke Power Co. Oconee 2

Duke Power Co. Oconee 3

OPPD Ft. Calhoun 1

Baltimore Electric

& Gas Calvert Cliffs 1

Metropolitan Edison Three Mile Island 1

Indiana & Michigan

Electric D.C. Cook 1 Indiana & Michican

Electric D.C. Cook 2

Northeast Utilities Millstone 2

Portland General

Electric Trojan 1

Toledo Edison Davis Besse 1

Arkansas Power &

Light Arkansas Nuclear One 2

WPPSS Hanford 1

IE Information Notice No. 79-37 Enclosure

December 28, 1979

RECENTLY ISSUED

IE INFORMATION NOTICES

Information Subject Date Issued To

Notice No. Issued

79-36 Computer Code Defect In 12/31/79 All holders of power reactor

Stress Analysis of Piping OLs and CPs

Elbow

79-35 Control of Maintenance 12/31/79 All power reactor facilities

and Essential Equipment with an OL or CP

79-34 Inadequate Desiqn of 12/27/79 All holders of power reactor

Safety-Related Heat OLs and CPs

Exchanaers

79-33 Improper Closure of 12/21/79 All power reactor facilities

Primary Containment holding OLs and CPs

Access Hatches

79-32 Separation of Electrical 12/21/79 All power reactor facilities

Cables for HPCI and ADS holding OLs and CPs

79-31 Use of Incorrect Amplified 12/13/79 All holders of power reactor

Response Spectra (ARS) OLs and CPs

79-30 Reportinq of Defects and 12/6/79 All power reactor facilities

Noncompliance, 10 CFR Part 21. holding OLs and CPs and

vendors inspected by LCVIP

79-29 Loss of NonSafety-Related 11/16/79 All power reactor facilities

Reactor Coolant System holdino OLs or CPs

Instrumentation During

Operation

79-28 Overloading of Structural 11/16/79 All power reactor facilities

Elements Due to Pipe Support with an OL or CP

Loads

79-27 Steam Generator Tube 11/16/79 All power reactor facilities

Ruotures At Two PWR holdina OLs and CPs

Facilities79-12A Attemoted Damaqe To New 11/9/79 All Fuel Facilities, Fuel Assemblies research reactors, and

oower reactors with an

OL or CP