ML19256B470
| ML19256B470 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 06/20/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Tallman W PUBLIC SERVICE CO. OF NEW HAMPSHIRE |
| References | |
| NUDOCS 7907110391 | |
| Download: ML19256B470 (1) | |
Text
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NUCLEAR REGULATORY COMMISSION
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KING OF PRUSSIA, PENNSYLVANIA 15406 631 PARK AVENUE 9 *****
June 20, 1979 Docket Nos. 50-443 50-444 Public Service Company of New Hampshire ATTN: Mr. W. C. Tallman President 1000 Elm Street Manchestar, New Hampshire 03105 Centlemen:
This Infonnation Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the infomation 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 this office.
Sincerely, lh
~
oyce H. Grier Director
Enclosures:
1.
IE Information Notice No. 79-17 2.
List of IE Information Notices Issued in 1979 cc w/encls:
John D. Haseltine, Project Manager 835 097 2 son.to9M
ENCLOSURE 1 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Information Notice No. 79-17 Date:
June 20, 1979 Page 1 of 2 SOURCE HOLDER ASSEMBLY DAMAGE FROM MISFIT BETWEEN ASSEMBLY AND REACTOR UPPER GRID PLATE Description of Circumstances:
Recently, the NRC was informed of a problem at two Westinghouse PWR facilities resulting from an apparent misfit.,etween secondary source holder assemblies and the reactor upper grid plate.
The misfit problem was first identified cy Carolina Pcwer & Light, licensee for H. B. Robinson Unit 2, who informed the NRC on May 6, 1979, of the circum-stances.
During che current refueling outage at H. B. Robinson 2, CP&L deter-mined that two tacondary source holder assemblies had been damaged during ti.e previous refueling in February 1978, by a misfit between the assembly and the reacter 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 containing 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-tion also resulted in some bencing 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 from Westinghouse.
Subsequently, the licensee's inspection revealed that the source 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 assembly 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 ghei%%irhhMnhIb%1acL.w.y of sufficient clearance for these source' "
only at the core locations which contair DUPLICATE DOCUMENT Entire document previously entered 1
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