ML19211C123
| ML19211C123 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 12/28/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 8001100103 | |
| Download: ML19211C123 (1) | |
Text
g># RE%q(o q{Q UNITED STATES y
y g
g y.,,
g NUCLEAR REGULATORY COMMISSION g.f ' "
'c REGION V o, s a
1990 N. CALIFORNI A BOULEVARD D
,o SUITE 202, WALNUT CREEK PLAZA e,,,*
WALNUT CREEK, CALIFORNI A 94596 December 28, 1979 Docket No. 50-312 Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention: Mr. John J. Mattimoe Assistant General Manager Gentlemen:
This Information Notice is provided as an earl, notification of a possibly significant matter.
It is expected that recipients will review the information for possible applicability to their facilities.
flo specific action or response is requested at this time.
If NRC evaluations so indicate, further licensee actions may be requested or required.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely,
%2W R. H. Engelken Director
Enclosures:
1.
IE Information Notice No. 79-37 2.
List of Recently Issued IE Information Notices cc w/ enclosures:
R. J. Rodriguez, SMUD 1738 295 L. G. Scnwieger, SMUD 8001100/0 3
UNITED STATES ISINS N0.: 6870 NUCLEAR REGULATORY COMMISSION Accession No.:
0FFICE 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 Circunstances:
An anonymous letter was received by the Director of the Office of Inspection and Enforcenent, 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.
Westinahouse had made a presentation on the turbine disc crackina to electric utility executives on October 30, 1979.
Telephone discussions between the NRC staff and Westinahouse's Turbine Division on November 20, 1979 established that crackina, attributed to stress corrosion ohenomena, had been found in the keyway areas of several LP turbine discs at operatinq plants and that inservice inspection techniques (i.e., in situ ultra-sonic examination) for crack detection have been developed and 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 Commonwealth 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 areater depth than the keyway cracks found to date.
Accordina to Westinghouse, these bore cracks have been metallurgically examined and preliminary findinas 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 meetina was held on December 17, 1979 between the NRC staff, Westinghouse and utility representatives to discuss the disc crackina problem, repair alter-natives, turbine missile evaluation, inspection techniques and plant inspection priorities.
In response to the staffs' request, Westinghouse provided the staff an updated report on December 21, 1979 reaarding the current field inspection oroaram that included a list of nuclear power plants already inspected, recom-mended inspection schedules and peetinent 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 make repairs before the plants return to power. Point Beach returned to power on December 23, 1979 with a small crack in the No. 2 disc o Westinghouse indicated that the observ DUPLICATE DOCUMENT durina 28 additional months of turbine the turbine inspection results and ana Entire document previously entered into s stem u der:
h
((
ANO 1738 2?6 No. of pages: