ML20084S441

Ro:On 710915,control Rod Drives 4 & 31 Were Opened & Failed to Drop.Caused by Deposit of Foreign Matl in Clutch Face. Addl Drive Packages Removed & Clutch Faces Reworked

ML20084S441
Person / Time
Site:	Palisades
Issue date:	09/24/1971
From:	Haueter R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084S436	List: ML20084S441
References
NUDOCS 8306170007
Download: ML20084S441 (2)

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ReptetNr A, 1c41 Irr . Pe'er A. Morris, 'Mra~ tor Pe- Ncket fio 50-255 Divisien of Heartor Licensing License Ne DP5 20 US Atomic Energy ocnission Palisades Plant Washington, Dc 20545 ,

Derzr '1r . Mor r i s :

,i This letter its written to apprise you of two recent occur-rences involving the control rod drive system at this facility.

At the time of the two events, the reactor was critical at a 10 k4 power level and primary system conditions were:

Baron Concentration 1220 ppe Temperature 532 F Pressure 2100 psia Primary Coclant Pumps in service 3 (cut of h)

Low Power Physics Testing ~

in progress The first incident occurred at ih03 on September 15, 1971, when the test switch to the clutch power supply of control rod drive mechanism number L was opened at the control rod drop test panel (a step in the test procedure) and the control rod failed to drop.

The circuitry was checked and found to be in order. At this point, the rod was dropped by applying a slight force to the lower half of the clutch. The control rod drive was then drop-tested 10 times from the test panel wJthout incident (average drop times were 1.2 to 1.3 seconds).

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Low power physics testing was then resumed and involved droppind each control rod individually into the core. Baron concen- l tration in the primary coolant was maintained at a level whereby any ona of the forty-five control rods withdrawn would be capable of bringing the core suberitical.

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',- UJ Atocic Energy Cormission 3eptember 2h, 1971 The second incident occurred at 1908 on 3eptembe- 15, 1971.

Tne rod drop test switch for control rod drive mechanism number 31 ww open e and this control rod failed to drop immediately ( 13 seconde censurrd b-tcre reaahing the 7CI core insertion point).

Again, as in the case of contrcl rod drive mechanicm nurWer 4, epeated drop tests of the control red number 31 resulted in normal Pop times.

All single-con +rel-rod-drop tests were completed and the resator secured with all control rods fully inserted to allow the removal of drive packase numbers h and 31 for examination to determine the cause for the observed malfunctions.

CAU3E OF INCIDEWS Examination of the clutch surfaces in the drive package of control rod drive mechanism numbers 4 and 31 disclosed a slight deposit of a material appearing to be epoxy as well as some foreign material. The clutch face in drive package number k contained the largest concentration of the material (approximately 1/16 x 1/8 inch).

These deposits were located so as to hamper the free movement of the spring loaded moveable clutch face.

The conclusion reached was that the epoxy application during the installation of new spring and pins on the magnetic clutch in v. arch 1971 was excessive. Evidence indicates some of the substance flowed into the spring holes in the lower clutch face and in some cases to the spline area below the springs.

CORRECTIVE ACTION PLAIMED Additional drive packages were removed and the clutch faces reworked the week of September 20, 1971, during which time the primary coolant system was at ambient temperature and atmos-pheric pressure to allow primary coclant pump seal (s) replacement.

The remainder of the drive packa before initiating any further testing and/ges or are to be training operator reworkedin utilizing the reactor. All springs will be replaced to preclude a change in spring constants by prior deposits of epoxy. Any appli-cation of epoxy to lock the spring pins in place will be controlled so as to prevent any of the substance from entering the spring holes.

Yours very truly,

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1 IMI/ERC/mhe '\ R. L. Haueter

_ ;' lectric Production Superintendent - Nuclear CC: BHGrier '

.USAEC Compliance, COO )Y I