ML19273B642
| ML19273B642 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 05/07/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 7906120079 | |
| Download: ML19273B642 (1) | |
Text
ug UNITED STATES
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((pa atoc NUCLEAR REGULATORY COMMISSION W2A
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611 RYAN PLAZA DRIVE, SUITE 1000 o
REGIGN IV o, 4 f
ARLIN GTON, TE X AS 76011 1, -
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f May 7, 1979 In Reply Refer To:
RIV Docket Nos.
50-445/IE Information Notice No. 79-11 50-446/IE Information Notice No. 79-11 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,
[/
Karl V. S rit C
Director
Enclosures:
1.
IE Infonnation Notice No. 79-11 2.
List of IE Information Notices Issued in 1979 2350 153 79061200 77 Q
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 IE Information Notice No. 79-11 Date: May 7, 1979 Page 1 of 1 LOWER REACTOR VESSEL HEAD INSULATION SUPPORT PROBLEM Virginia Electric and Power Company, North Anna Power Station No. I reported on November 8,1978, a field modification pertaining to the lower vessel head insulation support system which was not seismically analyzed at the time of modification. A subsequent stress analysis indicated that the ASME Code allowable stress and the :'ald stress for the operating base earthquake (0BE) on some of the instrument guide tubes were exceeded.
For the North Anna No. I field modification, the lower vessel head insulation was supported by angle brackets that are clamped onto the gridwork to about 20 of the 53 instrument guide tubes. This additional load on the guide tubes was not considered in the original stress analysis.
The maximum stress occurs in the socket welds between the Thimble guide tubes and the Instrumentation nozzles that penetrate' the vessel.
The maximum stress was about 70 percent of the ultimate and, therefore, violation of the pressure bounda.y would not be expected.
VEPC0 plans to modify the supporting arrangement by building a framework underneath the insulation, which will take the loading off the guide tubes.
All holders of operating licenses and/or construction pennits should be aware of the potential problem of exceeding the allowable stress and the yield stress for OBE.
This 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 the matter, please contact the Director of the appropriate NRC Regional Office.
No written response to this information notice is required.
2350 154 7906060158
IE Information Notice No. 79-11 May 7, 1979 LISTING OF IE INFORMATION NOTICES ISSUED IN 1979 Information Subject Date Issued To Notice No.
Issued 79-01 Bergen-Paterson Hydraulic 2/2/79 All power reactor Shock and Sway Arrestor facilities with an Operating License (OL) or a Construc-tion Permit (CP) 79-02 Attempted Extortion -
2/2/79 All Fuel Facilities Low Enriched Uranium 79-03 Limitorque Valve Geared 2/9/79 All power reactor Limit Switch Lubricant facilities with an Operating License (0L) or a Construc-tion Permit (CP) 79-04 Degradation of 2/16/79 All power reactor Engineered facilities with an Safety Features Operating License (0L) or a Construc-tion Pennit (CP) 79-05 Use of Improper Materials 3/21/79 All power reactor In Safety-Related Camponents facilities with an Operating License (0L) or a Construc-tion Permit (CP) 79-06 Stress Analysis of 3/23/79 All Holders of an Safety-Related Piping Reactor Operating License (0L) or a Construction Permit (CP) 79-07 Rupture of Radwaste 3/26/79 All power reactor Tanks facilities with an Operating License (0L) or a Construc-tion Permit (CP)
Enclosure Page 1 of 2 2350 155
IE Information Notice No. 79-11 May 7, 1979 79-08 Interconnection of 3/28/79 All power reactor Contaminated Systems with facilities with an Service Air Systems Used Operating License As the Source of Breathing (0L) and Pu Proces-Air sing fuel facilities 79-09 Spill of Radioactively 3/30/79 All power reactor Contaminated Resin facilitiec with an Operating License (0L) 79-10 Nonconforming Pipe 4/16/79 All power reactor Support Struts facilities with a Constructica
'Parmit (CP) 2350 156 Enclosure Page 2 of 2