ML19273B668
| ML19273B668 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 05/07/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Gerstner W ILLINOIS POWER CO. |
| References | |
| NUDOCS 7906120111 | |
| Download: ML19273B668 (1) | |
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otes ettys. iouNois coia7 Docket No. 50-461 Docket No. 50-462 Illinois Power Company ATTN:
Mr. W. C. Gerstner Executive Vice President 500 South 27th Street Decatur, IL 62525 Gentlemen:
- rhis IE Information Notice No. 79-11 is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the information for possible appli-cability 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 this office.
Sincerely, M /)$
_bs G. Kep er Director
Enclosure:
IE Information Notice No. 79-11 cc w/ encl:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Mr. Dean Hansell, Office of Assistant Attorney General 2350 202 1
7906120)))
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT REGION III May 7, 1979 IE Information Notice 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 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 yield stress for the operating base earthquake (OBE) on some of the instrument guide tubes werc 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 boundary would not be expected.
VEPCO 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 NRC evaluations so indicate, an IE Circular or Bulletin will be issued to recommend or request specifi: licensee actions.
If you have questions regarding the matter, please contact the Director of the appropriate NRC Begional Office.
No written response to this information notice is required.
2350 203
Enclosure:
Listing of IE 7006060158 Information Notices Issued in 1979
4 IE Information Notice No. 79-11 May 7, 1979 LISTING OF IE INFORMATION NOTICES ISSUED IN 1979 Information Subj ect 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 Atte?pted 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 OL or a CP 79-04 Degradation of 2/16/79 All power reactor Engineered facilities with an Safety Teatures 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 79-06 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 Nonconforming Pipe 4/16/79 All power reactor Support Struts facilities with a CP 2350 204 Enclosure Page 1 of 1