ML19256B471
| ML19256B471 | |
| Person / Time | |
|---|---|
| Site: | Sterling |
| Issue date: | 06/20/1979 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Arthur J ROCHESTER GAS & ELECTRIC CORP. |
| References | |
| NUDOCS 7907110392 | |
| Download: ML19256B471 (1) | |
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UNITED STATES
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KING OF PRUSSIA, PENNSYLVANI A 194C6 9.....,e June 20, 1979 Docket No. 50-485 Rochester Gas & Electric Corporation ATIN: Mr. J. E. Arthur Chief Engineer 89 East Avenue Rochester, NY 14649 Gentlemen:
This Information Notice is provided as an early notificatir.n 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 thic 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 off u.
Sincerely, h
n Boyce H. Grier
" Di rector
Enclosures:
1.
IE Information Notice No. 79-17 2.
List of IE Information Notices Issued in 1979 cc w/encls:
C. R. Anderson, Manager, QA Lex K. Larson, Esquire N. A. Petrick, Executive Director, SNUPPS Gerald Charnoff, Esquire Mb 099 70071105Pg
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ENCLOSURE 1 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WAS iINGTON, 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 holdar assemblies had been damaged during the previous refueling in February 1978, by 3 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 some bending of the fuel rods in the assembly, however, in no case did this bending result in fuel clKding perforation.
On May 16, 1979, the licensee of D. C. Cook Unit 1 informed the tF that the present refueling outage would be extendcd 15 to 20 daj: to remove the reactor head, which had already been reinstalled following completion or 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 wi+5 the vanes.
The source holder was removed from one assembly readily wi+' no apparent damage while in the other the source holder was found str.k 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 pof L *_ Locations in the assembly not i
filled with a source or burnable poison ~ "
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