ML19224C464
| ML19224C464 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 06/20/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Howell S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 7907020421 | |
| Download: ML19224C464 (1) | |
Text
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UNITED STATES E '",, jl',g NUCLEAR REGULATORY COMMISSION c
REGION 111
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,o" GLEN E L'.YN, ILLINOIS 60137 JiN 2 01979 Docket No. 50-329 Docket No. 50-330 Consumers Powar Company ATTN:
Mr. Stephen H. liowell Vice President 1945 West Parnall Road Jackson, MI 49201 Gentlemen:
This Informat ion Notice No. 79-17 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 the Director of this office.
Sincerely, b$
James G. Ke er Director
Enclosure:
IE Information Notice No. 79-17 cc w/ encl:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Ronald Callen, Michigan Public Service Commission Dr. Wa3 E. North Myron M. Cherry, Chicago 271 312 790799.yo, Q,
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U.S. NUCLEAR kEGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT REGION III June 20. 1979 IE Information Notice No. 79-17 SOURCE HOLDER ASSEMBLY DAMAGE FROM MISFIT BETWEEN ASSEM"LY AND REACTOR LTPER GRID PLATE Description of Circumstances:
Recently, the NRC was infor=ed of a problem at two Westinghouse PWR f acilities 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 da= aged 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 deforretion of the upper grid plate com-ponents at the core location and of the source holder assemblies. The deforma-tion also resulte.d in some bending of the fuel rods in the essembly, however, in no case did this bending result in fuel cladding perforation.
On May 16, 1979, the licensee of D. L. Cook Unit 1 informed the NRC that the present refueling outage would be extended 15 tci 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 ocher the source holder wac 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 core. Each such control assemblies and placed at symmetrical locations in t' assembly contains a metrical grouping of four secondary source rods and between zero and tw.ty burnable poison rods. Locations in the assembly nat filled with a source or burnable poisoed="*_ a rhivhl ege. The lack of sufficient clearance for these sou
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