Cook (USA)

Map of Cook

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2 PWR units : with a capacity of 1000 and 1100 MW contructed by Westinghouse, operating since 1975 and 1978.

Facilities in Cook

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The main turbine, the generator and a low-pressure turbine have been damaged. The incident was caused by broken blades on two of the unit's three low-pressure turbines which generated vibrations that consequently damaged parts of the NPP. The reactor will return to service on Sept 2009 at the earliest.


One worker was injured when equipment failure resulted in a fire in the switchyard outside the nuclear power plant, and therefore there was an activation of an alert.
Under the U.S. Nuclear Regulatory Commission's emergency classifications, an alert involves "an actual or substantial degradation of safety... and no public action is required."
The fire was brought under control within an hour.


Officials at Indiana Michigan Power Co. (IMP) this week were expecting the NRC to approve their use of an alternate repair technique for fixing cracks in alloy 600 vessel head penetrations at DC Cook-2, the first such repairs in a US vessel head.
The alternate repair technique Cook has proposed already was approved by NRC in February for use at Virginia Power Co.'s North Anna-1 during that unit's 30-day outage, which ended March 11. However, no crack indications were found at North Anna during its first inspection so the repair procedure was not used.
Under the code-endorsed repair option, the crack indication can be cut out of the tube wall, assuming there is sufficient wall thickness remaining. The weld overlay put in later could not be thicker than 5 mm.
D. Powell, manager of mechanical systems at Cook, said Westinghouse is reinspecting the No. 75 penetration, a thermocouple instrument column, on the Cook vessel head, that was found to have crack indications during a fall 1994 inspection. The penetration had three axial crack indications then with the most significant being about 42% throughwall, versus a 75% throughwall safety limit.


During refueling loose bolts have been found in the unit's former plate, which stands between the fuel assemblies and the core barrelectrical The former plate is secured to the core barrel by 8 rings of 80 bolts each (the 890 mm bolts are made of stainless steel). If bolts break off they can damage fuel and other components.
In a 1992 outage workers found 1 bolt had come loose and fallen to the bottom of the RPV.


During outage some small cracks were found at RPC head penetrations. These were the first ever found in an US RPV.


Unit was returning from refueling when excessive vibration in the turbine forced it off line. Rotor had to be removed and was shipped to Brown Boveri for further testing.


Design errors in the EDG room ventilation systems could render the EDGs inoperable during tornado.


design errors in the EDG room ventilation systems could render the EDGS inoperable dudring tornado.


All 4 main steam isolation valves may have been inoperable because of excessive condensate accumulation on the vent side of the MSIV operaing piston.


Failure of a 120VAC instrument bus caused reactor trip. Partial loss of control room instrumentation and failure of 1 train of plant protection system.


Failure of studs on anchor darling check valves.


Failure of studs on anchor darling check valves.


Throttle valves were found locked closed during test of the boron injection system.