ML20085F720

AO 75-019:on 750830,control Rod 11 Dropped Into Core.Caused by Shorted Clutch Coil.Clutch Replaced

ML20085F720
Person / Time
Site:	Palisades
Issue date:	09/09/1975
From:	Bixel D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Purple R Office of Nuclear Reactor Regulation
Shared Package
ML20085F724	List: ML20085F720 ML20085F730
References
A-75-19, A0-75-019, NUDOCS 8308230152
Download: ML20085F720 (3)

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@ J j o.ne,.i o, .c o. 2,2 w .e u.cs.gan Avenue, Jackson Michigan 49201 e Area Cor1e 517 7RO 05$O Ceptember 9, 19'(5 Mr Robert A. Purple Division of Henetor Licensing US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255, LICENSE DPR PALIDADES PLANT, A0-75-19 Attached is Abnormal Occurrence (AO) Report No 75-19 covering dropped shutdown rod No 11. This occurrence appears to be similar to A0-75-18 and an investign-tion into the cause of these failures has begun.

O David A. Bixel (Signed)

David A. Bixel Assistant Nucient Licensing Administrator CC: .IGKeppler, USNRC File 8308230152 750909 PDR ADOCK 05000255 bb58 S PDR 00PY SENT REGION 2

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O AB!!0RMAL OCCURRENCE REPORT Palieades Plant

1. Report No: A0-75-19.

2. a. Report Date: Sept 9, 1975

b. Occurrence Date: August 30, 1975.

3 Facility: Palisades Plant, Covert, MI.

4. Identification of Occurrence: Control Rod No 11 dropped into the core.

This incident was identified as an abnormal occurrence by Technical Specifications 3.10.6(c). The shutdown rods shall not be inserted below their exercise limit until all regulating rods are inserted.

5. Conditions Prior to Occurrence: The plant was operating at the steady state power level of 80%.

6. Description of Occurrence: At 0811 hours0.00939 days <br />0.225 hours <br />0.00134 weeks <br />3.085855e-4 months <br /> on August 30, 1975, Control Rod No 11 dropped into the core. Turbine runback reduced plant power to 70%.

Plant power was further reduced to 60%.

7 Designation of Apparent Cause of Occurrence: The apparent cause of the incident was a shorted clutch coil.

8. Analysis of Occurrence: Control Rod No 11 was classified inoperable under Section 3.10.h(b) of the plant Technical Specifications. Plant operation can continue with one inoperable rod.

Core flux tilts were calculated to be 7% to 8% which is within the limits of Technical Specification Section 3.10.3. Reactivity of the dropped rod was less than 0.2%. (Technical Specifications limit on potential ejected rod worth is 15.)

9 Corrective Action: The immediate corrective action was to replace the clutch.

While the dropping of a control rod is an anticipated event provided for within the plant Technical Specifications (and generally does not represent ti safety problem), we recognize that a generic problem may exist with the control rod drive mechanism (CRDM) clutches. In an effort to resolve this problem, we have begun an investigation of the clutch failures that have recently occurred and hope to determine the mode and/or cause of the failures.

Clutch coil operating conditions are being checked as a part of this investi-gation.

10. Failure Data:

a. CRDM No 11 manufacturer is Combustion Engineering, Inc and the piece O is J-2966-163-001.

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O The dual clutch assembly manufacturer is Combustion Engineering, Inc l and the piece number is CND-SE-3998-1.

b. This mode of failure on CRDM clutches has occurred in the past at the l Palisades Plant. See A0-73-9 transmitted by letter dated August 20,  ;

1973 and A0-75-18 transmitted by letter dated August 28, 1974. l i

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