05000206/LER-1982-003, Forwards LER 82-003/99X-0.Detailed Event Analysis Submitted

Forwards LER 82-003/99X-0.Detailed Event Analysis Submitted

ML20042A887
Person / Time
Site:	San Onofre
Issue date:	03/05/1982
From:	Ray H SOUTHERN CALIFORNIA EDISON CO.
To:	Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML20042A888	List: 05000206/LER-1982-003, Forwards LER 82-003/99X-0.Detailed Event Analysis Submitted 05000206/LER-1982-003-99, /99X-0:on 811212,control Rod C-7 Stuck During Startup & Was Freed After Repeated Manipulation.Caused by Dropped Rodlets Due to Failure of Weld Attaching Supporting Vane to Rod Cluster Control (RCC) Hub.Rcc to Be Replaced
References
NUDOCS 8203240243
Download: ML20042A887 (2)

LER-1982-003, Forwards LER 82-003/99X-0.Detailed Event Analysis Submitted

Event date:
Report date:
2061982003R00 - NRC Website

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Attention: fir. R. H. Engelken, Director M

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DOCKET No. 50-206 P

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Dear -Si r:

This letter describes an occurrence involving one of our Rod Cluster Control Assemblies (RCCA). This occurrence is not reportable in accordance with the requirements of Provisional Operating License DPR-13 but is con-sidered significant and is, therefore, being provided for your information.

On December 11, 1981, the reactor was shutdown from equilibrium conditions at 86% power for minor repairs to the secondary system. Reactor power was returned to 86% on December 12, 1981.

During this startup, the RCCA in core position C-7 stuck and was freed after repeated manipulations. At the time, this was thought to be a problem with a loose lift coil fuse clip.

Normal surveillance of incore thermocouple readings disclosed a step change in the core position area of C-7.

Specifically, C-6 decreased by about 1.4* F, C-5 by about 0.6* F, and C-8 by about 0.7* F.

Flux maps prior to shutdown were compared to flux maps after startup for position C-6 for the same Control Bank position and for different positions.

Changing Control Bank positions significantly altered the flux shape. With the same bank position, the flux map after startup displayed the same shape but a 3% decrease in magnitude with respect to previous maps.

The reactivity effect was estimated to be less than 50 pcm using normal reactivity follow procedures.

Our reactor vendor, Westinghouse, identified the probable cause to be a This failure mode results in full insertion of the affected vane and ro failure of the weld attaching a vane supporting two rodlets to the RCC hub.

while the remainder of the RCC assembly remains operable. Similar problems have been observed at Connecticut Yankee, D. C. Cook 1, Robinson 2, and KORI.

//

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4 Mr. R. H. Engelken March 5, 1982 Analyses of reactor coolant samples before and after the event indicated no detectable Silver 110-m. These analyses indicate that the rodlet cladding which contains the Silver-Indium-Cadmium absorber material is intact.

INCORE analysis confirms that reactor peaking factors have not been significantly affected and remain within limits. Westinghouse has verified the acceptability of continued operation.

Currently, we glan to remove and replace the RCCA in core position C-7 during the next ref ueling outage. The fuel assembly at this core location is in its second cycle and will probably be used in a low flux region during the next cycle.

Westinghouse has indicated that this failure is not a generic concern.

Several RCCA's will be inspected during the next refueling outage as a part of the normal Reactor Internals Inspection Program. These inspections include visual examination of the hub to vane connections.

If you should require additional information, please contact me.

Sincerely,

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Enclosure: Licensee Event Report 82-003 cc:

U. S. Nuclear Regulatory Commission Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Office of Management Information & Program Control (MIPC)

Institute of Nuclear Power Operations Nuclear Safety Analysis Center L. F. Miller (USNRC San Onofre Unit 1 Resiacnt Inspector)