ML19224C470
| ML19224C470 | |
| Person / Time | |
|---|---|
| Site: | 05000484 |
| Issue date: | 06/20/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dienhart A NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 7907020433 | |
| Download: ML19224C470 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION
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'" /. E REGION 111 8
799 ROOSEVELT ROAD o
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8 GLEN FLLYN, IL LINOls 60137 y'w j
JUN 2 01979 Dock:.t No. 50-484 No'rthern States Power Ccmpany ATTN:
Mr. A. V. Dienhart Vice President - Tyrone Energy Park 100 North Barstow Street Eau Claire, WI 54701 Gentlemen:
This Informarion Notice No. 79-17 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 this office.
Sincerely,
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8[amesG.Kepper Director
Enclosure:
IE Information Notice No. 79-17 cc w/ encl:
Central Files Director, NPR/Di'M Director, NRR/ DOR PDR Local PDR NSIC TIC Regions I & IV q73 iqg i/ I
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U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT REGION III June 20, 1979 IE Information Notice No. 79-17 SOURCE HOLDER ASSEMBLY DAMAGE FROM MISFIT BETWEEN ASSEMBLY M D REACTOR UPPER GRID PLATE Description of circumstances:
Recently, the NRC was informed of a problem at two Westinghouse PWR facilities resulting fron an apparent misfit between secondary source holder assemblics and the reactor upper grid plate.
The misfit problem was first identified by Carolina Power & Light, licensee for H. B. Robinson Unit 2, who informed the NRC on May 6, 1979, of the circum-stances. During the current refacling outage at H. B. Robinson 2, CP&L deter-miTed that two secondary source holder assemblies had been da= aged during the previous refueling in February 1978, by a misfit between the assembly and the reactor upper grid plate. The misfit resulted from insufficient clearance (i.e. 1/2 to 3/4 inch) between the source holder assembly hub and the grid plate at the core locations c ataining thermocouple mixing vanes. This lack of sufficient clearance caused minor deformation of the upper grid plate com-ponents at the core location and of the source holder assemblies. The deforma-tian also resulted in some bending of the fuel rods in the assembly, however, in no case did this bending result in fuel cladding perforation.
On May 16, 1979, the licensee of D. C. Cook Unit 1 informed the NRC that the present refueling outage would be extended 15 to 20 days to remove the reactor head, which had already been reinstalled following completion of refueling, to correct this misfit problem. They learned of.the problem fro Westinghouse.
Subsequently, the licensee's inspection resealed that the sou.ce holder assembly hubs were in contact with the vanes. The source holder was removed from one assembly readily with no apparent damage while in the other the source holder was found stuck in the assembly. The problem was corrected prior to return to operations.
The secondary source asse.mbly rods are normally inserted into rod cluster control assemblies and placed at symmetrical locations in the core. Each such assembly contains a symmetrical grouping of four secondary source rods and between zero and twenty burnable poison rods. Locations in the assembly not filled with a source or burnable poison rod conta_n a thimble plug. The lack of sufficient clearance io.: thase se only at the core locations which cor DUPLICATE DOCUMENT 271 329 Entire document previously entered into system under:
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