ML19273B633
| ML19273B633 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 05/07/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Humphreys L GULF STATES UTILITIES CO. |
| References | |
| NUDOCS 7906120065 | |
| Download: ML19273B633 (1) | |
Text
b r* Mc UNITnD STATES oq'o 3
4 NUCLEAR REGULATORY COMMISSION
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REGION IV E
611 RYAN PLAZA DRIVE, SUITE 1000 AR LINGTON, TEXAS 76011 May 7, 1979 In Reply Refer To:
RIV Docket Nos.
50-458/IE Information Notice No. 79-11 50-459/IE Information Notice No. 79-11 Gulf States Utilities Attn: Mr. L. L. Humphreys Senior Vice President, Energy Development Post Office Box 2951 Beaumont, Texas 77704 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 quettions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely,
(
c m
n Karl V. 5 t it Director Enclosurcs:
1.
IE Information Notice No. 79-11 2.
List of IE Information Notices Issued in 1979 2350 125 790612006F
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 Pcwer 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 (.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 chat 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 Instreaentation 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 infonuation 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 126 7906000158
IE Infonnation 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 (0L) 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 (OL) or a Construc-tion Permit (CP) 79-04 Degradation of 2/16/79 All power reactor Engineered facilities with an Safety Features Operating License (OL) or a Construc-tion Pennit (CP) 79-05 Use of Improper Materials 3/21/79 All power reactor In Safety-Related Components 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 127
IE Information Notice No. 79-11 May 7, 1979 79-08 Interconnection of 3/28/79 All power reactor Contaminate;: Systems with facilities with an Service Air Systems Used Operating License As the Source of Breathing (UL) and Pu Proces-Air sing fuel facilities 79-09 Spill of Radioactively 3/30/79 All power reactor Contardinated Fesin facilities with an Operating License (0L) 79-10 Nonconforming Pipe 4/16/79 All power reactor Support Struts facilities with a Construction
' Permit (CP) 2350 128 Enclosure Page 2 of 2