ML19339B335
| ML19339B335 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/10/1980 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 8011060757 | |
| Download: ML19339B335 (1) | |
Text
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c osc UNITED STATES
- p oq'o NUCLEAR REGULATORY COMMISSION
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REGloN IV E I S
611 RYAN PLAZA DRIVE, SUITE 1000
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October 10, 1980 In Reply Refer To:
RIV Docket Nos.
50-445/IE Inf.ormation Notice No. 80-36 50-446/IE Information Notice No. 80-36 Texas Utilities Generating Company ATTN: Mr. R. J. Gary, Executive Vice President and General Manager 2001 Bryan Tower Dallas, Texas 75201 Gentlemen:
This IE Information Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the information 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,
?
f Karl V. Seyfrit /f Director
Enclosures:
1.
IE Information Notice No. 80-36 2.
List of Recently Issued IE Information Notices e
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T amu e0W av eu SSINS No.:
6835 Accession No.:
8006190085 UNITED STATES NUCLEAR REUULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Information Noti e No.: 80-36 Date: October
- 1980 Page 1 of 2 FAILURE OF STEAM GENERATOR SUPPORT BOLTING Description of Circumstances:
On September 4, 1980, the NRC staff was informed by the Northern States Power Company that extensive cracking of the bolting for the supports attached to the bottom of the steam generators on Prairie Island Unit I had occurred. The licensee initially discovered the bolting problem when two bolts failed during detensioning. The licensee was attempting 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 inch diameter 250 ksi maraging steel bolting (Vascomax 250).
Ultrasonic exat aation 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 subsequently shut down the Prairie Island Unit 2 facility and performed ultrasonic examinations of the same steam generator 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. Magnetic particle examinations confirmed the results of the ultrasonic exacinations 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 ultrasonic examination of the affected bolting had been performed previously.
In the case of Unit I a significant number of the bolts were examined at the last refueling outage 14 months ago.
No cracks were found at that time.
The susceptibility for stress corrosion cracking was identified in NUREG-0577 (for comment). The NUREG identifies those facilities which have utilized maraging steels for reactor coolant pump and steam generator support bolting.
Further the NUREG recommends augmented inspections for the facilities included in Group I.
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IE Infc.rmation Notice October 10, 1980 No. 60-36 Page 2 of 2 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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IE Information No. 80-36 October 10, 1980 LISTING OF RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued To Notice No.
Issued 80-29 Broken Studs on Terry 8/7/80 All light water reactor Turbine Steam Inlet facilities holding Flange power reactor Operating i
License (OL) or Construc-tion Permit (CP) 80-30 Potential for Unaccept-8/19/80 All boiling water reactor able Interaction Between facilities holding power the Control Rod Drive Scram reactor Operating Licenses i
Function and Non-Essential (OLs) or Construction Control Air at Certain GE BWR Permits (cps)
Facilities 80-31 Maloperation of Gould-8/27/80 All light water reactor Brown Boveri Type 480 facilities holding volt type K-600S and Operating Licenses or and K-DON 600S circuit Construction Permits breakers (cps) 80-32 Clarification of certain 8/12/80 All NRC and agreement requirements for Exclu-state licensees sive-use shipments of radioactive materials 80-33 Determination of Tele-9/15/80 All teletherapy therapy Timer Accuracy (G3) licensees 80-34 Boron Dilution of Reactor 9/26/80 All Pressurized Coolant During Steam Water Reactor Generator Decontamination Facilities holding power reactor Operating Licenses (OLs) 80-35 Leaking and Dislodged 10/10/80 All categories G and Iodine-124 Implant Seeds G1 medical licensees Enclosure
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