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On April 19, 2002, with the plant operatin … On April 19, 2002, with the plant operating at approximately 99.5 percent power, a turbine trip resulted in an automatic reactor trip when a temperature switch in the Stator Water Cooling System tripped on a high value. The temperature switch in the Stator Water Cooling System was found with a trip setpoint value approximately 14°C lower than the acceptance criteria found in the calibration procedure.</br></br>Following the reactor trip, main steam reheat valves, 2-MS-2A and 2-MS-2B, did not close as expected and had to be manually closed, resulting in an unexpected RCS cooldown. Auxiliary Feedwater automatically initiated to compensate for a low level in the Steam Generators caused by shrinkage. Required safety equipment functioned as expected and this event is considered to be of low safety significance.</br></br>The cause of this event is indeterminate. The presumptive causes are either an equipment failure or insufficient oversight and controls that led to calibration errors.</br></br>Following the reactor trip, the temperature switch was tested and re-calibrated to the proper setpoints prior to plant restart. To prevent recurrence the stator coolant temperature switch from both Millstone Unit Nos. 2 and 3 will be replaced. The Unit No. 2 device will then be sent to the vendor for a failure analysis. In addition, separate procedures will be developed for secondary plant instruments that are trip sensitive at Unit Nos. 2 and 3.t are trip sensitive at Unit Nos. 2 and 3. +
April 19, 2002 +
On April 19, 2002, with the plant operatin … On April 19, 2002, with the plant operating at approximately 99.5 percent power, a turbine trip resulted in an automatic reactor trip when a temperature switch in the Stator Water Cooling System tripped on a high value. The temperature switch in the Stator Water Cooling System was found with a trip setpoint value approximately 14°C lower than the acceptance criteria found in the calibration procedure.</br></br>Following the reactor trip, main steam reheat valves, 2-MS-2A and 2-MS-2B, did not close as expected and had to be manually closed, resulting in an unexpected RCS cooldown. Auxiliary Feedwater automatically initiated to compensate for a low level in the Steam Generators caused by shrinkage. Required safety equipment functioned as expected and this event is considered to be of low safety significance.</br></br>The cause of this event is indeterminate. The presumptive causes are either an equipment failure or insufficient oversight and controls that led to calibration errors.</br></br>Following the reactor trip, the temperature switch was tested and re-calibrated to the proper setpoints prior to plant restart. To prevent recurrence the stator coolant temperature switch from both Millstone Unit Nos. 2 and 3 will be replaced. The Unit No. 2 device will then be sent to the vendor for a failure analysis. In addition, separate procedures will be developed for secondary plant instruments that are trip sensitive at Unit Nos. 2 and 3.t are trip sensitive at Unit Nos. 2 and 3. +
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June 18, 2002 +
April 19, 2002 +
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