ML19261E286
| ML19261E286 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 06/20/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Eric Turner HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 7907050509 | |
| Download: ML19261E286 (1) | |
Text
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June 20, 1979 In Reply Refer To:
RIV Docket Nos. 50-498/IE Information Notice No. 79-17 50 ^99/IE Information Notice No. 79-17 Houston Lighting & Power Company ATIN:
Mr. E. A. Turner, Vice President Power Plant Construction and Technical Services Post Office Box 1700 Houston, Texas 77001 Centlecen:
This IE Information Notice is provided 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 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
.u have questions regarding this matter, please contact the Director of the appropriate Ni:C Regional Office.
Sincerely, pt t-Karl V. Seyfri Director
Enclosures:
1.
IE Information Notice No. 79-17 2.
List of IE Information Notices Issued in 1979
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UNITED STATES NUCLEAR REGULATORY COMMISEIN 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 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 thermocouple mixing vanes.
This lack of sufficient clearance caused minor deformation 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 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 reinstal'.ed following completion of refueling, to correct this misfit problem.
They learned of the problem from Westinghouse.
Subsequently, tha licensee's inspection revealed that the source holder assembly bubs were in contact with the vanes.
The source holder was removed from one assembly readily with no apparent damage, while in the other, th? 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 paison rods.
Locations in the assemb1v not fji_11ggg _ m source or burnable poison rod contain a
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