Sequoyah (USA)

Map of Sequoyah

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2 * 1100 MW PWR units; constructed by Westinghouse; grid connection in 1980/81

Facilities in Sequoyah

plantreactor typconstruction startoperation startshut down
Sequoyah-1PWR19701980
Sequoyah-2PWR19701981
1995-02-23

WITH UNIT 1 AT 100% POWER, LEAK INTO
CONTAINMENT TO BE 11 TO 19 lit/min. PRESSURIZER LEVEL DROPPED FROM 60
TO 57%; VOLUME CONTROL TANK LEVEL DROPPED FROM 63%; REACTOR BUILDING SUMP LEVELS INCREASED; RADIATION MONITOR IN THE INCORE INSTRUMENT ROOM INDICATED HIGH. A RADIATION CONTROL TECHNICIAN OBSERVED STEAM AND WATER IN THE INCORE INSTRUMENT ROOM BY LOOKING THROUGH THE AIR LOCK DOOR OBSERVATION GLASS.
WITH POWER AT 5%, UNIT 1 RECEIVED A CONTROL ROD URGENT FAILURE ALARM INDICATING A PROBABLE PROBLEM IN THE ROD CONTROL CABINETS. CONTROL ROOM OPERATORS MANUALLY TRIPPED THE REACTOR. ALL CONTROL RODS INSERTED COMPLETELY AND STEAM IS BEING DUMPED TOTHE MAIN CONDENSER. UNIT IS STABLE HOT STANDBY.

1994-07-05

4 month refueling outage and 10-year-inspection; replacement of 1250 m secondary side piping (to avoid errosion corrosion wear). Replacement of seals of the RCP- pump seals.

1994-01-07

Nach nur 20 Tagen Betrieb mußte die Anlage wieder abgeschalten werden, um ein Wasserstoffleck zu flicken und den Schaft einer Pumpe der Komponentenkuehlung zu tauschen.

1993-03-01

Rupture of the 10 " -diameter steam extraction line from turbine -> manual scram. Break was due in part to failure of the erosion-corrosion detection computer program to predict the problem.

1992-10-26

Water entrained in the control air system resulted in turbine runbacks at both units and a scram at unit 1, failure of a FRV

1992-10-26

Water entrained in the control air system resulted in turbine runbacks at both units.

1992-03-20

11 of the 48 ice condenser doors could not be opened without excessive force. (ice condenser tubes are supposed to open during a severe accident, exposing baskets of ice on which radioactive steam will condense)

1992-03-19

51 mm circumferential crack was found in a SG FW line. Water was leaking from the crack at a rate of 20 lit/min.

1990-10-08

Three check valves downstream of 3 MSIVS failed; the valve discs sheared from the hinge pin assembly, could have prevented the MSIVS from closing during a DBA due to reverse flow conditions