ML20092D692

Ro:On 840419,standby Gas Treatment Trains Inoperable.Caused by Const Bulldozer Shearing Off Fire Hydrant,Causing Fire Protection Sys to Lose Pressure.Charcoal Adsorbers Replaced. Procedures Controlling Const Activities Implemented

ML20092D692
Person / Time
Site:	Cooper
Issue date:	04/20/1984
From:	Peter Thompson NEBRASKA PUBLIC POWER DISTRICT
To:	Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
CNSS840154, NUDOCS 8406220106
Download: ML20092D692 (2)

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COOPER NUCLEAR STATION Nebraska Public Power District "" " ""d" *o"J%%""^>"^ "'"

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CNSS840154 April 20, 1984 Mr. John T. Collins, Regional Administrator \

U.S. Nuclear Regulatory Commission M AW Region IV

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611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76011

Dear Mr. Collins:

This event summary is submitted in accordance with NUREG 0654, Appendix 1 and CNS Emergency Plan Impicmenting Procedure (EPIP) 5.7.2 to close out the Notification of Unusual Event declared at 1140, April 19, 1984.

At approximately 1015, April 19, 1984 with reactor power at about 70%, a construction bulldozer sheared off a fire hydrant in the north yard of the CNS restricted area. This caused the fire protection system to lose pressure to approximately 10 psig. The fire pumps in service were secured at the direc-tion of the Operations Supervisor until the broken fire hydrant could be isolated. Once the hydrant was isolated at about 1025, the fire pumps were returned to service and the fire protection system pressure was restored.

At 1034, the Shift Supervisor was informed by Control Room personnel that high moisture alarms on both Standby Gas Treatment (SBGT) trains had been annunciated in the Control Room. Apparently when the fire protection system pumps were returned to service, a water hammer effect was created on the clappers of the SEGT automatic deluge system valves. This water hammer forced the clappers open, sprinkling the SBGT charcoal filters. Local inspection of the SBGT units verified that the installed fire deluge systems had been activated and had flooded the charcoal adsorbers, rendering both SBCT trains inoperable.

Both SBGT trains were declared inoperabic by the Shif t Supervisor at 1035. At that point, the Limiting Condition for Operation (LCO) established in Technical Specification 3.7.B.4 had been entered. This Specification stipulates that under the then existing conditions " . . . procedures shall be initiated immediately to establish reactor conditions for which the standby gas treatment system is not required." Such conditions required that the plant be placed in cold shutdown. At 1100, procedures were initiated for normal plant shutdown and power reduction was commenced.

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. Mr.,J;hn T. Collins

• April 20, 1984 Page 2 Having entered a Technical Specification LCO requiring plant shutdown, the Shif t Supervisor assumed duties as Emergency Director and declared a Not ifica-tion of Unusual Event at 1140, based on Initiating Condition 6.1 of CNS EPIP 5.7.1. Appropriate notifications were initiated in accordance with EPIP 5.7.6 and were completed by 1156. At 1400, with reactor power at approximately 34%,

the reactor was manually scrammed. Ilot shutdown conditions were established and an orderly cooldown of the reactor was commenced to place the reactor in cold shutdown.

At 2215, the Shutdown Cooling Mode of the Residual lleat Removal System was placed in service and, by approximately 2315, reactor coolant temperature was less than 212*F. At 2324, the vessel head vents were opened, establishing cold shutdown conditions.

11aving established cold shutdown conditions, the LCO for Technical Specifica-tion 3.7.B.4 was satisfied. The Emergency Director the. upon terminated the Notification of Unusual Event at 2325. Closecut notifications were initiated in accordance with CNS EPIP 5.7.2 and 5.7.6. These notifications were completed by 2336.

Immediate plans call for replacing the SBGT charcoal adsorbers, testing to prove Technical Specification requirements for SBCT are met and plant startup to resume power operations. Longer term plans include an engineering evaluation of the SBGT automatic deluge system and a review of procedures for controlling the activities of construction contractors.

Sincerely,

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, . V. Thomason j Division Manager of Nuclear Operations PVT: DAW:1b cc: L. G. Kunci