ML20090E293

AO 73-11-29:on 731126,15 Control Rod Drives Failed to Insert to Position 00 Following Reactor Scram.Caused by Leakage Past Stop Piston Seals

ML20090E293
Person / Time
Site:	Nine Mile Point
Issue date:	12/03/1973
From:	Schneider R NIAGARA MOHAWK POWER CORP.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20090E243	List: ML20090E273 ML20090E293
References
8728, AO-73-11-29, NUDOCS 8303140586
Download: ML20090E293 (1)

Text

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O.

O NIAGARA MOH AWK POWER CORPORATION NIAGARA MOHAWK

, 300 Efest souLEVARD WEST SYRACU S E. N. Y.13202 December 3, 1973 ,

ADR 73-11-29 pt Mr. Donald J. Skovholt g Assistant Director for Reactor Operations Division of Reactor Licensing I ${k (yb g Jg hP, '

United States Atomic Energy Commission S- 4;, '

Washington, D. C. 20545 Af',*g 1 Re: Provisional Operating License: DPR-17 /

Docket No.: 50-220 i

Dear Mr. Skovholt:

On November 26,1973 at 0330 hours0.00382 days <br />0.0917 hours <br />5.456349e-4 weeks <br />1.25565e-4 months <br /> at Nine Mile Point Nuclear Station Unit #1, fifteen (15) control rod drives failed to insert to position 00 following a reactor scram. Persuant to Technical Specifications: 1.13 d,

d. Failure of one or more components of an engineered safety feature or Station system that causes or .

threatens to cause the feature or system to be 1 incapable of performing'its intended function, this is an abnormal occurrence and was reported by telephone and photocopy to Director of Regulatory Operations, Region I.

Prior to the occurrence the unit was being shutdown, mode switch in start-up and reactor pressure.was less than 850 psig. A scram occurred on neutron instrumentation (IRM's) and upon resetting the scram fifteen (15) control rods showed position 02. Seven (7) of those were the subject of AOR 73-11-20. The operator immediately inserted these control rods to 00 using normal drive pressure and the manual control system.

The apparent cause of this occurrence following a review of testing by SORC has been identified as leakage past the stop piston seals.

The reactor was shutdown even with fifteen (15) control rods at 02 as indicated by decreasing neutron instrumentation therefore no hazard was presented to the general public nor was plant safety in jeopardy.

i To correct this situation, the fifteen -(15) control rods will be over-hauled during the Spring 1974 refueling outage. This is the second incident l of this nature (AOR 73-11-20) and appears to be a problem which occurs as a l result of deteriorating stop piston seals causing a slewdown during the last, ,

5% of drive travel. . H 8303140586 740114  :).

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• PDR ADOCK 05000220 g truly yours,- /g Syg

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