Cooper (USA)

Map of Cooper

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780 MW BWR unit constructed by GE, in operation since 1974.

Facilities in Cooper

plantreactor typconstruction startoperation startshut down

Cooper operators waited about 20-25 minutes before notifying their supervisors, that they had inserted the wrong control rods into the core. Though operators restored the proper core pattern in 45 minutes, the incident has raised serious concerns at NRC about the forthrightness of the crew at the Nebraska Public Power District (NPPD) plant.
Cooper has been a subject of NRC concern in recent years. The agency sent a special team to the plant in 1994 after a series of incidents raised concerns about what NRC perceived as a lax attitude among workers.


Crews at Cooper plant discovered this month that modifications made to an emergency diesel generator in 1994 to meet NRC fire protection rules would have actually rendered that generator inoperable during a control room fire.
Cooper was down for a routine refueling and maintenance outage when the wiring error was found.
The wiring mistake was made in August 1994.


HPIS declared inoperable because of potential water hammer conditions. Plant was at 100% power when the fault was found. Roughly 400 liters of water were discovred in the loop area of the exhaust line, where only about 10 liters should be. Restart after modifications.


Restart ending the forced outage that began 9 months ago and cost more than 10 million $ for replacement power alone. An attempt to restart the plant days earlier fizzled when faulty valves that were installed during the outage brought the plant down from 5% power. ( 3 of the 6 safety relief valves in the automatic depressurization system would not manually open).


Forced outage after it was learned that workers had installed inoperable circuit breakers in the EDGs; Plant was down 8 month ( costing 8 million US$ in replacement power) - the maintanance fault was not an isolated problem - an NRC safety evaluation team among other problems was concerned about the RCS, CR room filtration system and the EDG. - restart in February 1995.


Reactor core isolation cooling system: steam supply valve failed closed after a successful pump operability test. Grease in the spring pack prevented from compressing, thus the torque switch remained closed.


Reactor tripped after MSIV drifted shut following a rupture of an instrument air dryer.