ML19224C480
| ML19224C480 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 06/20/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Short T OMAHA PUBLIC POWER DISTRICT |
| References | |
| NUDOCS 7907020445 | |
| Download: ML19224C480 (1) | |
Text
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UNITED STATES
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June 20, 1979 Docket No.
50-285 Omaha Public Powar District ATTN:
T.
E. Short, Assistar t General Manager 1623 Harney ot'eet Omaha, Nebrasia 68102 Gentlemen:
This IE Information Notice is provided as an early notifi.ation of a possibly significar c matter. It is expected that recipients will review the informa-tion for possible applicability to their facilities.
No specific action or response is requested at this tima.
If further NRC evaluations so indicate, an IE C;rcula'. or Bulletin will be issued to recommend or request specific licensee actions.
If you have questions regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, Karl V. Seyfr*t Director
Enclosures:
1.
IE Information Notice No. 79-17 2.
List of IE Information Notices Issued in 1979 cc:
R. L. Andrews, Manager Fort Calhoun Station Post Office Box 98 Fort Calhoun, Nebraska 68102 272 003 790702o 9'y5
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 PL1TE Description of Circumstances:
Recently, the NRC was informed of a problem at two Westinghouse PWR facilities resulting from an apparent misfit between secondary so"rce holder assemblies and the reactor upper grid plate.
The misfit problem wa urst 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 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 components at the core location and of the source holder assemblies.
The deformation 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 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 other, the source holder was found stuck in the assembly.
The problem was corrected prior to return to ope rations.
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.
Loca-
% ee g ly not filled with a source or burnable poison rud contain DUpLIC
'cient clearance for these sc.irce holder asse T
locations which contain thermocouple r Entire d into syst ent previous 1 under.
Y entered ANO ]h 9022o 272 004
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