ML19224C481
| ML19224C481 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 06/20/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Millen C PUBLIC SERVICE CO. OF COLORADO |
| References | |
| NUDOCS 7907020446 | |
| Download: ML19224C481 (1) | |
Text
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PDR:HQ 9p UNITED STATES h
g Nc NUCLEAR REGULATORY COMMISSION 5 /Wl@p e.h REGION IV 2
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June 20, 1979 Docket. No.
50-267 Public Service Corapany of Colorado ATTN:
Mr. C. K. riillen Senior Vice President P. O. Box 840 Denver, Colorado 80201 Gentlemen:
This IE Information Notice is providea as an early notification of a possibly significant matter.
It is expected that recipients will review the informa-tion for possible applicability to their facilities. No specific action or response is request 2d at this time.
If further NRC evaluations so indicate, an IE Circular or Bulletin will be issued to recommend or request specific licensea actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely,
[ }l l'
Karl V. Seyfri Director
Enclosures:
1.
IE Information Notice No. 79-17 2.
List of IE Information Notices Issued in 1979 D. W. Warembourg, Nuclear Production cc:
Manager Fort St. Vrain Nuclear Station P. O.
Box 368 Platteville, Colorado 80651 L. Brey, Manager, Quality Assurance 2?722 (igf4 272 005 790702 0 t/ z/ 4
UNITED STATES NUCM AR 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 ASSEllBLY DAMAGE FROM MISFIT BETWEEN ASSEMBLY AND REACTOR UPPER GRID PLATE Description of Circumstances:
Recently, the NRC was infomed of a problem at two Westinghouse PWR facilities resulting from an apparent misfit between secondary source holder assemblies 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 refueling outage at H. B. Robinson 2, CP&L deter-mined that two secondary source holder assemblies had been damaged 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 containing themoccuple mixing vanes.
.., la c k o f sufficient clearance caused minor defomation of the upper grid plate components at the core location and of the source holder assemblies.
The deformation also resulted in some bending of the fuel rods in the assembly, however, in no case did this bending cesult 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 vtended 15 to 20 days to remove the reactor head, which had already been reinstalled Mllowing 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 rod contain T-M o n%.
The lack of sufficient clearance for these source holder asse
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