ML19261E283
| ML19261E283 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 06/20/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Weigand J GULF STATES UTILITIES CO. |
| References | |
| NUDOCS 7907050506 | |
| Download: ML19261E283 (1) | |
Text
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- 'o, UNITED STATES UkSU E f.g 7 c '(
NUCLEAR REGULATORY COMM!SSION D, ; M,-'
c HEGION IV D, (N
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Gil RYAN PLAZA DRIVE, SUITE 1000
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ARLINGTON, TEXAS 76012 June 20, 1979 In Reply Refer To:
RIV Docket Nos.
50-458/1E Informatior. Notice No. 79-17 50-459/IE Information Notice No. 79-17 Gulf States Utilities Attn:
Dr. J. G. Weigand General Manager, Kuclear Projects Post Office Box 2951 Beaumont, Texas 77704 Gentlemen:
This IF 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 you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely,
/
p Karl V. Seyfr'it Director
Enclosures:
1.
IE Information Notice No. 79-17 2.
List of IE Information Notices Issued in 1979 O
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 IE Info,rmation Notice No. 79-17 Date: June 20, 1979 Page 1 of 2 SOURCE HOLDER ASSEMBU 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 tror' 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 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 cont-;ns 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 burar'd e poison rod contaif clearance for
.e source holder as DUPLICATE DOCUMENT locations which contain thermocouple
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