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On July 5, 2011, at 1815 hours, it was det … On July 5, 2011, at 1815 hours, it was determined that a design deficiency at the Perry Nuclear Power Plant (PNPP) constituted a fire protection program concern which could adversely affect the ability to achieve and maintain safe shutdown of the plant in the event of a control room fire. (Reference event notification numbers 46811 and 46997). In the event of a postulated control room fire, the potential exists that two 4160 VAC breakers could trip open under a hot-short condition.</br>PNPP's Appendix R design vulnerability only affects Breakers EH1106, which supplies the Emergency Service Water Pump A and EH1107, which supplies the Control Complex Chiller A. Specifically, the current transformers used in these breakers for the 50/51 instantaneous and time over current protective relays are in line with the component control room ammeters. Therefore, a hot-short-to-ground in the associated control room ammeters could actuate the 50/51 relays and trip the component breaker.</br>Actions are in progress to isolate the control room ammeters for the Emergency Service Water Pump A in breaker EH1106 and the Control Complex Chiller A in breaker EH1107. Isolating these ammeters would isolate the affected circuitry from the described Appendix R failure mechanism. Control room amperage indication for the pump and chiller would be lost while this Temporary Modification is installed. PNPP will pursue a permanent resolution to the hot-short-to-ground fault for the EH1106 and EH1107 breakers.</br>This event is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B), as a condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety. A follow-up licensee event report will be made in 60 days. The resident inspector has been notified. The resident inspector has been notified. +
22:15:00, 5 July 2011 +
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20:35:00, 5 July 2011 +
22:15:00, 5 July 2011 +
On July 5, 2011, at 1815 hours, it was det … On July 5, 2011, at 1815 hours, it was determined that a design deficiency at the Perry Nuclear Power Plant (PNPP) constituted a fire protection program concern which could adversely affect the ability to achieve and maintain safe shutdown of the plant in the event of a control room fire. (Reference event notification numbers 46811 and 46997). In the event of a postulated control room fire, the potential exists that two 4160 VAC breakers could trip open under a hot-short condition.</br>PNPP's Appendix R design vulnerability only affects Breakers EH1106, which supplies the Emergency Service Water Pump A and EH1107, which supplies the Control Complex Chiller A. Specifically, the current transformers used in these breakers for the 50/51 instantaneous and time over current protective relays are in line with the component control room ammeters. Therefore, a hot-short-to-ground in the associated control room ammeters could actuate the 50/51 relays and trip the component breaker.</br>Actions are in progress to isolate the control room ammeters for the Emergency Service Water Pump A in breaker EH1106 and the Control Complex Chiller A in breaker EH1107. Isolating these ammeters would isolate the affected circuitry from the described Appendix R failure mechanism. Control room amperage indication for the pump and chiller would be lost while this Temporary Modification is installed. PNPP will pursue a permanent resolution to the hot-short-to-ground fault for the EH1106 and EH1107 breakers.</br>This event is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B), as a condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety. A follow-up licensee event report will be made in 60 days. The resident inspector has been notified. The resident inspector has been notified. +
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