ML19224C474
| ML19224C474 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 06/20/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Bryan J UNION ELECTRIC CO. |
| References | |
| NUDOCS 7907020438 | |
| Download: ML19224C474 (1) | |
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.lVN 2 01979 Docket No. 50-483 Docket No. 50-486 Union Electric Company ATTN:
Mr. John K. Bryan Vice President - Nuclear P. O. Box 149 St. Lou i.s, MO 63166 Gentlemen:
This Information Notice No. 79-17 is provided as an ea-ly netification 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 furthe- *sC 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, AY James G. Kep~p er Director
Enclosure:
IE Information Notice No. 79-17 cc w/ encl:
Mr. W. H. Weber, Manager, Nuclear Construction Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Region I & IV Ms. K. Drey lion. C. J. Frass, Chairman Missouri Public Service Commission 271 336
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7 U.S. NUCLEAR REGULATORY COMMISSION OFFICE dF INSPECTION AND ENFORCEMENT REGION III June 20, 1979 IE Information Notice No. 79-17 SOUFCE HOLDER ASSEMILY DAMAGE FROM MISFIT BETWEEN ASSEMBLY AND REACTOR UPPER GRID PLATE Description of Circumstances:
Recently, the NRC was informed of a problem at two Westinghouse FWR 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.I. 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, CP6L 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 com-ponents at the core location and of the source holder assemblies. The deforma-tion also resulted in some bendin; of the fuel rods in the a.:sembly, 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 miafit 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 helder was removed from one assembly readily with no apparent damaga while in the other the source holder was four.d stuck in the assembly. Ine problem was corrected prior to return to operations.
The secondary source assembly rods are normally inserted into rod cluster control assembliec 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 N 'pble_ plug. The lack M"'
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of sufficient clearance for these source only at the core locativas which contain DUPLICATE DOCUMENT
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