ML19224D306
| ML19224D306 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 05/07/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Stampley N MISSISSIPPI POWER & LIGHT CO. |
| References | |
| NUDOCS 7907110331 | |
| Download: ML19224D306 (1) | |
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UN2TED STATES pm R800g'o NUCLEAR REGULATORY COMM!tSION
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MAY 7 1979 In Reply Refer To:
MJP4 6,50-417]
Mississippi Power and Light Company Attn:
Mr. Norris L. Stampley Vice President of Production P. O. Box 1640 Jackson, Mississippi 39205 Gentlemen:
This Information Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients vill 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 vill be issued to recoc=end or request specific licensee actions.
If you have ques-tions regarding this catter, please contact the Director of the appro-riate NRC Regional Office.
Sincerely, b
Director
Enclosure:
1.
IE Information Notice No. 79-11 2.
Draft Transmittal Letter cc w/ encl:
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L. Nail, Plant Superintendent P. O. Box 756 Port Gibson, Mississippi
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 May 7, 1979 IE Inforcation Notice No. 79 11 LO'a'ER REACTOR VESSEL HEAD INSULATION SUPPORT PROBLEM I
Virginia Ele.cric and Power Cocpany, North Anna Power Station No.
reported en Nove=ber 8, 1978, a field modification pertaining to the lower vr.ssel head insulation support system which was not seis=ically analy7ed at the time of modification. A subsequent stress analysis the ASME Code allowable stress and the yield stress for indicated that the operating base earthquake (OBE) on some of the instrument guide tubes were exceeded.
1 field modification, the lower vessel head For the North Anna No.
insulation was supported by angle brackets that are cla= ped onto the of the 53 instrument guide tubes. This additional gridwork to about load on the guide tubes was not considered in the original stress analysis.
The maximum stress occurs in the socket velds between the Thimble guide tubes and the Instru=entation nozzles that penetrate the vessel.
The maxieum stress was about 70 percent of the ultimate and, therefore, violation of the pressure boundary would not be expected.
VEPCO plans to modify the suppcrting arrange =er.t by building a frateverk underneath the insulation, which vill 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 It is expected that recipients will review possibly significant matter.
No the information for possible applicability to their facilities.
If further NRC specific action or response is requested at this ti=e.
evaluations so indicate, an IE Circular or Bulletin will be issued to reco==end or request specific licensee actions.
If you have questions the Director of the appropriate NRC regarding the matter, please contact Regional Office.
No written response to this inforcation notice is required.
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Enclosure IE Information Notice No. 79-11 Page 1 of 1 May 7, 1979 LISTING OF IE INFORMATION NOTICES ISSUED IN 1979 rate Issued To Information Subject Issued Notice No.
79-01 Bergen-Paterson Hydraulin 2/2/79 All power reactor facilities with an Shock and Sway Arrestor OL or a 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 facilities with an Limit Switch Lubricant OL or a CP 79-04 Degradation of 2/16/79 All power reactor facilities with an Engineered OL or a CP Safety Features 79-05 Use of Improper Materials 3/21/79 All power reactor facilities with an in Safety-Related Components OL or CP 79-06 Stress Analysis of "3/23/79 All Holders of Reactor OL or CP Safety-Related Piping 79-07 Rupture of Radvaste 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 Syste=s Used OL and Pu Processing fuel facilities As th; hource of Breathing Mr 79-09 Spill of Radioactively 3/30/79 All power reactor facilities with an Contaminated Resin OL 79-30 Nonconforcing Pipe 4/16/79 All power reactor facilities with a Support Struts CP T
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