ML19256B468
| ML19256B468 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 06/20/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Boyer V PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| NUDOCS 7907110379 | |
| Download: ML19256B468 (1) | |
Text
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UNITED STATES g - pA 3 y73., c ',g NUCLEAR REGULATORY COMMISSION r
REGION I
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631 PARK AVENUE S, '
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,f MING OF PROS 31A, PENNSYLVANIA 19406 June 20, 1979 Docket Nos. 50-352 50-353 Philadelphia Electric Company ATTN:
Mr. V. S. Boyer Vice President Engineering and Research 2301 Market Street Philadelphia, PA 19101 Gentlemen:
This Information Notice 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 this office.
Sincerely,
.m
- _r fY oyce
'H. Grier
" Director
Enclosures:
1.
IE Infonnation Notice No. 79-17 2.
List of IE Information Notices Issued in 1979
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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 between secondary source holder assemblies and the reactor upper grid plate.
The misfit problem was first identified by Carolina Pcuer & Light, licensee for H. B. Robinson Unit 2, who informed the NRC on May 6, 1979, of the circum-stances.
During the current refueling cutage 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 holoer 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 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 we reactor head, which had already been ^einstalled following completion of refueling, to correct tnis misfit problem.
They learned of the problem from Westinghouse.
Subsequently, the licensee's inspection revealed that the source holder assembly hubs were in cont.ct 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 poi n-nm S -P a l m The lack of sufficient clearance for these sot
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only at the core locations which con.
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