ML19339B339
| ML19339B339 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 10/10/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 8011060763 | |
| Download: ML19339B339 (1) | |
Text
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'o UNITED STATES 8
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NUCLEAR REGULATORY COMMISSION g
j REGION V 1990 N. CALIFORNIA BOULEVARD
&g SulTE 202, WALNUT CREEK PLAZA 4,,g4 WALNUT CREEK, CALIFORNIA 94596 October 10, 1980 Docket flo. 50-312 Sacramento Municipal Utility District P. O. Box 15830 Sacramento, California 95813 Attention: Mr. John J. Mattimoe Assistant General Manager Gentlemen:
This Information flotice is provided as an early notification of a possibly significant matter.
It is expected that recipients will revie.i the infor-mation for possible applicability to their facilities.
No specific action or response is requested at this time.
If further NRC evaluations so indicate, an IE Circular or Bulletin will be issued to recommend or request specific licensee actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, l
tewce-u fL R. H. Engelken Director
Enclosures:
1.
IE Information Notice flo. 80-36 2.
List of Recently Issued IE Information Notices cc w/ enclosures:
R. J. Rodriguez, SMUD L. G. Schwieger, SMUD 7011000 floS Q
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8006190085 Ifl 80-36 UflITED STATES f!UCLEAR REGULATORY C0fitilSSI0ft OFFICE OF IllSPECTI0tl AtlD EflFORCEf4EtlT WASHIf!GT0ft, D.C.
20555 October 10, 1980 i
IE Information ?!otice flo. 80-36:
FAILURE OF STEAf4 GEtlERATOR SUPPORT BOLTIflG Description of Circumstances:
On September 4,1980, the flRC staff was informed by the florthern States Power Company that extensive cracking of the bolting for the supports attached to bottom of the steam generators on Prairie Island Unit 1 had occurred. The licensee initially discovered the bolting problem when two bolts failed during detensioning. The licensee was attemptina to remove the pre-loau on the bolting (specified at 1400 ft-lbs) to minimize the potential for stress corrosion cracking of the high strength 1-1/2 in, dia.
250 ksi maraging steel bolting (Vascomax 250).
Ultrasonic examination of the support bolting revealed cracks or breaks in 47 of 48 support bolts for the two steam generators at the Prairie Island Unit 1 i
facility. The licensee subseouently shut down the Prairie Island Unit 2 facility and performed ultrasonic examinations of the same steam generator i
support bolting, that failed on Unit 1.
The results of the UT examinations revealed cracks in three of the 48 steam generator support bolts. The licensee attempted to remove the cracked bolts from the steam generator supports.
Two cracked bolts were successfully removed while the third failed during removal.
Two bolts that were judged as defect free by the ultrasonic examination were
~
also removed. flagnetic particle examinations ccnfirmed the results of the i
ultrasonic examinations on the bolts which were removed. As part of the short term corrective actions taken, the licensee has unloaded and retensioned the bolting at approximately 50 to 100 ft.-lbs.
Inservice ult-.
examination of the affected bolting had been performed previously.
In t.Se case of Unit 1 a significant number of the bolts were examined at the last refueling outage.14 months ago.
fio cracks were found at that time.
The susceptibility for stress corrosion cracking was identified in flUREG-0577 l
(forcomment). The flVREG identifies those facilities which have utilized maraging steels for reactor coolant pump and steam generator support bolting.
4 Further the flVREG reccmmends augmented inspections for the facilities included in Group I.
Licensees are encouraged to review the bolting materials used at their respective facilities and consider inspection of maraging steel bolting that are either pre-loaded or'significantly loaded during operation.
This Information flotice is provided as an early notification of a possibly
- >ignificant matter that is still under review by the flRC staff.
It is expected that recipients will review the information for possible applicability to their facility. ?!o specific action or response is requested at this time.
If you have any questions regarding this matter, please contact the Director of
.the appropriate flRC Regional Office.
O s
IN 80-36 October 10, 1980 RECE!!TLY ISSUED IE It! FORMATIO!! NOTICES Information Date of
?!otice flo.
Sub.iect Issue Issued to 80-35 Leakina and dislodged 10/10/80 All categories G and Iodine-124 inolant seeds G1 medical licensees 80-34 Boron dilution of reactor 9/26/80
' All pressurized water coolant during steam reactor facilities generator decortamination holding power reactor OLs 80-33 Ceterninatior of teletheracy 9/15/80 All teletherapy tirer accuracy (G3) licensees 80-32 Clarificaticn of certain 8/12/80 All flRC aret agreement reauirerents for Exclu-stata lic6Esees sive-use snipments of radioactive materials 80-31 Maloperation of Gould-8/27/80 All light water reactor Crown Boveri Type 480 facilities holding OLs volt tyce K-600S and or cps K-DC ! 600S circuit breakers 80-30 Potential for unaccept-8/19/80 All boiling water reactor able interaction between facilities holding power the control rod drive scram reactor OLs or cps.
function and ncn-essential control air at certain GE BUR facilities 80-29 Croken studs on Terry 8/7/80 All light water reactor turbine steam inlet facilities holding flange power reactor OLs or cps
- Supplement to I!ctification of 7/29/80 All holders of reactor 80-06 significant events at and near-tern OL operatinq power reactor applicants facilities 80-28 Prorpt renorting of 6/13/80 All applicants for and required infornation holders of nuclear power to !!P.C reactor cps 80-27 Degradation of reactor 6/11/80 All pressurized water coolant pump studs reactor facilities holding power reactor OLs or cps
- Operating Licenses or Construction Permits