ML19224C485
| ML19224C485 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/20/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Johari Moore SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 7907020450 | |
| Download: ML19224C485 (1) | |
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UNITED STATES f-
[' g NUCLEAR REGULATORY COMMISSION y j'" '.,, gg/
s r,,.,; \\ r' Y REGION V 8
1990 N C AllFORNI A DOULEVARD O
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SUITE 202, WALNUT CREEK PLAZA o
WALNUT CREEK, CALIFORNI A 94596 June 20, 1979 Docket flos. 50-206 50-361 50-362 Southern California Edison Company P. O. Box 800 2244 Walnut Grove / venue Rosemead, Californih 91770 Attention:
Mr. Jack B. Moore Vice President 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 f1RC evaluations so indicate, an IE Circular or Bulletin will be issued to recommend or request specific licensee actions.
If you have questions regarding the matter, please contact the Director of the appropriate t'RC Regional Office.
Sincerely,
)
VTE $
dLl-L R. H. Engelken Director
Enclosure:
IE Information flotice No. 79-17 cc w/ enclosure:
J. M. Curran, SCE J. T. Head, SCE
^77 nj7 J. H. Drake, SCE d I l-Ui3 7 907030 t/SC
UNITED STATES NUCLEAR REGULATORY COMMISSION 0FFICE OF INSPECTION AilD ENFORCEMENT WASHINGTON, D.C.
20555 June 20, 1979 IE Information Notice No. 79-17 SOURCE HOLDER A5SEMBLY 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 Fabruary 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 com-ponents at the core location and of the source holder assemblies.
The deforma-tion also resulted in scme 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 Westinghou e.
Subsequently, the licensee's inspection revealed that the source holder assembly hubs were in contact witi 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 a thimble plug.
The lack of sufficient clearance for these s only at the core locations which cc ! DUPLICATE DOCUMENIz72 014
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