ML19339B348
| ML19339B348 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay, Diablo Canyon |
| Issue date: | 10/10/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 8011060779 | |
| Download: ML19339B348 (1) | |
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UNITED STATES
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. SUITE 202. WALNUT CREEK PLAZA WALNUT CREEK, CALIFORNIA 94596 October 10, 1980 Docket flos. 50-133, 50-275, 50-323 Pacific Gas and Electric Company 77 Beale Street 4
l San Francisco, California 94106 Attention: Mr. Philip A. Crane, Jr.
Assistant General Counsel 1
Gentlemen:
This Information flotice is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the infor-mation for possible applicability to their facilities.
fio specific action or response is requested at this time.
If further flRC 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 fiRC Regional Office.
Sincerely,
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/* ' R. H. E'ngelken U
Director
Enclosures:
1.
IE Information flotice flo. 80-36 2.
List of Recently Issued IE Information flotices cc w/ enclosures:
J. D. Shiffer W. Raymond, PG&E E. Weeks, PG&E, Humboldt Bay E. B. Langley, Jr., PG&E i
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8006190085 Irl 80-36 i
UtlITED STATES NUCLEAR REGULATORY COMftISSION OFFICE OF It!SPECTION AND EflFORCEMENT WASHINGTON, D.C.
20555 Octcber 10, 1980 IE Infomation flotice No. 80-36:
FAILURE OF STEAM GENERATOR SUPPORT BOLTING Description of Circumstances:
l On September 4,1980, the NRC staff was informed by the Northern States Power j
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 problen when two bolts failed during detensioning. The licensee was attemptina to remove the pre-load 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).
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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 facility. The licensee subseouently shut down the Prairie Island Unit 2
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facility and performed ultrasonic examinations of the same steam generator l
support bolting, that failed on Unit 1.
The results of the UT examinations revealed cracks in three of tha 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 confirmed the results of the ultrasonic examinations on the bolts which were removed. As part of the short i
term corrective actions taken, the licensee has unloaded and retensioned the bolting at approxir 3tely 50 to 100 ft.-lbs.
Inservice ultrasonic examination of the affected bolting had been performed i
previously.
In the case of Unit 1 a significant number of the bolts were examined at the last refueling outage 14 months ago.
No cracks were found at that time.
I i
The susceptibility for stress corrosion cracking was identified in NUREG-0577 (for comment). The NUREG _ identifies those facilities which have utilized i
4 maraging steels for reactor coolant pump and steam generator support bolting.
Further the NUREG reccmmends augmented inspections for the facilities included 4
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 Notice is provided as an early notification of a possibly significant matter that is still under review by the NRC staff.
It is expected-that recipients _will. review the information for possible applicability to their facility. No specific action or response is requested at this time.
If you have any questions regarding'this matter, please contact the Director of the appropriate NRC Regional Office.
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9 IN 80-36 October 10, 1980 RECEilTLY ISSUED IE INFCRMATION NOTICES Inf orma tion Date of Notice No.
Sub.iect Issue Issued to 80-35 Leakinq and dislodged 10/10/80 All categories G and Iodine-124 inplant seeds G1 cedical licensees 80-34 Boron dilution of reactor 9/26/80
' All pressurized water coolant during steam reactor facilities generator decontamination holding power reactor OLs 80-33 Ceternination of teletherany 9/15/80 All teletheracy tirer accuracy (G3) licensees 80-32 Clarification of certaia 8/12/30 All NRC and agreement reouirements for Exclu-state licensees sive-use shipments of radioactive materials 80-31 i!aloneration of Gould-8/27/80 All light water reactor Orcwn Eoveri Type 480 facilities holding OLs volt type K-600S and or cps K-DON 6005 circuit breakers 80-30 Potential for unaccept-3/19/80 All boiling water reactor able interaction between facilities holding power the control rod drive scram reactor OLs or cps.
function and non-essential control air at certain GE BUR facilities 80-29 Broken studs on Terry 8/7/30 All light water reactor turbine steam inlet facilities holding flange power ry.Ctor OLs or cps
- Supplement to Notification of 7/29/30 All holders of reactor 80-06 significant events at and near-tern OL oneratinn power reactor applicants facilities 80-28 Prompt reporting of 6/13/80 All applicants for and required information holders of nuclear power to i!RC reactor cps 80-27 Deqradation of reactor 6/11/80 All pressurized water coolant pump studs reactor facilities holding power reactor OLs or cps
- Operating Licenses or Construction Permits
.