ML19273B628
| ML19273B628 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 05/07/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| References | |
| NUDOCS 7906120053 | |
| Download: ML19273B628 (1) | |
Text
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I UNITED STATES 4
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NUCLEAR REGULATORY COMMISSION
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"Sacramente Municipal Utility District P. O. Box 15830 Sacramerto, California 95813 Attention: Mr. John J. Mattimoe Assistant General Manager Gentlemen:
This Infonration Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the information for possiole applicability to their facilities.
No specific acticn 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, b
R. H. Engelkea Director
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Enclosure:
7 IE Information Notice Q
No. 79-11 2350 115
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cc w/ enclosure:
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UNITED STATES NUCLEAR REGULATORY COPfilSSION 0FFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 May 7, 1979 IE Infornation flotice No. 79-11 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 pertalning to the lower vessel head insulation sunport system which was not seismically analyzed at the time of modification. A subsequent stress analysis
' e yield stress for indicated that the A5ME Code allowable stress and i
the operating base earthquake (OBE) on some of the.nstrument guide tubes were exceeded.
For the North Anna No.1 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 boundary 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 permits 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 flRC 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.
Enclosure:
2350 116 List of IE Information Notices Issued in 1979 1 of 1 7906060158
6 IE Information Notice flo. 79-11 Enclosure fiay 7,1979 Page 1 of 1 LISTING OF IE INFORf1ATION 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 OL or a CP 79-02 Attempted Extortion -
2/2/79 All Fuel Facilities I.ow Enriched Uranium 79-03 Limitorque Valve Geared ~
2/9/79 All power reactor Limit Switch Lubricant facilities with an OL or a CP 79-04 Degradation of 2/16/79 All power reactor Engineered facilities with an Safety Features OL or a CP 79-05
'Use of Improper Materials 3/21/79 All power reactor in Safety-Related Components facilities with an OL or CP 79-05 Stress Analysis of 3/23/79 All Holders of Safety-Related Piping Reactor OL or CP 79-07 Rupture of Radwaste Tanks 3/26/79 All power reactor facilities with an OL or CP 79-08 Interconnection of 3/28/79 All power reactor Contaminated Systems with facilities with an Service Air Systems Used OL and Pu Processing As the Source of Breathing fuel facilities Air 79-09 Spill of Radioactively 3/30/79 All power reactor Contaminated Resin facilities with an OL 79-10 Honconforming Pipe 4/16/79 All power reactor Support Struts facilities with a CP 2350 117