ML20084E964

Ro:On 720623,w/reactor at 5% Thermal Power,Control Board Received Alarms of Rod Bottom Rod Stop & Rod Control Urgent Failure Rod Stop.Caused by Water from Swagelok Fitting on Tubing Dropping on Rod Control Cabinets.Fitting Repaired

ML20084E964
Person / Time
Site:	Ginna
Issue date:	06/30/1972
From:	Amish K ROCHESTER GAS & ELECTRIC CORP.
To:	Bloch E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084E960	List: ML20084E964
References
NUDOCS 8304190085
Download: ML20084E964 (2)

Text

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June 30,1972

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Mr. Edward J. Bloch, Acting Director i

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Division of Reactor Licensing N U. S. . Atomic Energy Commission d (g'/. ,} in y

,W f 7920 Norfolk Avenue p~ 2" Bethesda, Maryland 20014 h ](({f g ,_I$/ L Subtect: Loss of power to control rods

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g; R. E. Ginna Nuclear Power Plant Unit No.1 'y}f N

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Docket 50-244 g( 77-- 4 ,7

Dear Mr. Bloch:

The Ginna unit was being returned to service following its refueling outage.

At approximately 2219 hours0.0257 days <br />0.616 hours <br />0.00367 weeks <br />8.443295e-4 months <br /> on June 23, 1972, with the reactor at five per-cent thermal power the control board received alarms of Rod Bottom Rod Stop

%d Rod Control Urgent Failure Rod Stop.

The Head Control Operator immediately manually tripped the full length control rods. The part length rods were out of the core. When the operator received the alarms he noted that the indicating rod bottom lights for the "B" Bank Control Group 2 Control Rods G S and G 9 were on and also that the position indicators for these two control rods were at zero.

Immediate investigation in the rod control cabinet area disclosed that water -

was dropping on top of these cabinets from the intermediate floor above. The source of water was found to be coming from a Swagelok fitting on the tubing-which transmits the main steam generator feedwater flow indication to the control room. The isolation valves to the transmitter were then closed.

The escaping water, which is condensate from the secondary system, had dropped through the floor above and followed in some cable trays to a position above Power Cabinet 2 BD. It then entered through penetrations on the top of the cabinet and grounded out the control power to the stationary .

gripper coils for Control Rods G 5 and G 9 which dropped these rods into the Core .

The power to the cabinet was turned off, the water wiped out and the cabinet.

thoroughly dried. Examination was made of the other full length rod control cabinets, both internally and above and these were found unaffected.

• Control Rods G S and G 9 were then each pulled 24" and manually tripped twice. All of Control Bank "B" control rods were pulled out ten steps and returned to zero. ~

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The Plant Operations Review Committee agreed that the control rods were Q ;PF B304190085 720627 '

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, s 3a Mr. I'dward J. Bloch operating properly and that the reactor could be returned to criticality. The time for this return was at 0635 hours0.00735 days <br />0.176 hours <br />0.00105 weeks <br />2.416175e-4 months <br /> on June 24, 1972 The feedwater flow transmission lines had been relocated during the refueling outage to accommodate the modification of the main steam safety valve support system. The Swagelok fitting was found to have been made up incorrectly and the complete fitting was replaced.

The committee has recommended that any holes in the floor above these rod drive cabinets be plugged, that deflection hoods over these cabinets be considered, and further that the maintenance force be reinstructed in the proper procedure of the installation of these compression fittings.

Very tr,uly yours,

p. c s h Lf I, Keith W. Amish xc: Mr. James P. O'Reilly J