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On March 3, 2016, during restoration of po … On March 3, 2016, during restoration of power to a Unit 1 electrical bus following planned work, an error in the restoration sequence resulted in an invalid auto-start signal to Emergency Diesel Generators (EDGs) 1, 2, 3 and 4. EDG 1 was out-of-service under clearance to support Unit 1 refueling outage modifications and maintenance and, as such, did not start. EDGs 2 and 4 auto-started as designed. However, EDG 3 failed to auto-start. At 1235 EST on March 4, 2016, EDG 3 was declared inoperable when troubleshooting identified a broken fuse block connection in the EDG 3 auto-start circuitry, which would have prevented a Technical Specification (TS) required auto-start of EDG 3. This condition concurrent with EDG 1 out-of-service would have precluded emergency power supply to emergency busses needed to mitigate the consequences of an accident.</br>Technical Specification 3.8.1, Required Action D.3, requires declaring the required features supported by the inoperable EDG 3 inoperable when the redundant required features are inoperable. As a result, both required Conventional Service Water (CSW) pumps were declared inoperable at 1635 EST on March 4, 2016. This also required declaring both Control Building Instrument Air Compressors inoperable. As a result, both Control Room Emergency Ventilation (CREV) subsystems and all three Control Building Air Conditioners were declared inoperable at 1635 EST on March 4, 2016.</br>The above conditions are reportable under 10 CFR 50.72(b)(3)(v)(D), as an event or condition that could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident. </br>This event did not result in any adverse impact to the health and safety of the public.</br>The risk significance of this event is considered to be low. Both EDG 2 and EDG 4 were available and protected, along with the supplemental diesel generator and offsite electrical sources. Except for the periods of time for repair activities and post-repair testing, EDG 3 remained available via manual start. Actions were taken to protect other redundant safety systems and additional defense-in-depth was provided.</br>EDG 3 was restored to Operable status March 4, 2016 at 1834 EST and this has restored the safety functions of the above mentioned systems.</br>The licensee notified the NRC Resident Inspector.ensee notified the NRC Resident Inspector.
17:35:00, 4 March 2016 +
51,769 +
20:02:00, 4 March 2016 +
17:35:00, 4 March 2016 +
On March 3, 2016, during restoration of po … On March 3, 2016, during restoration of power to a Unit 1 electrical bus following planned work, an error in the restoration sequence resulted in an invalid auto-start signal to Emergency Diesel Generators (EDGs) 1, 2, 3 and 4. EDG 1 was out-of-service under clearance to support Unit 1 refueling outage modifications and maintenance and, as such, did not start. EDGs 2 and 4 auto-started as designed. However, EDG 3 failed to auto-start. At 1235 EST on March 4, 2016, EDG 3 was declared inoperable when troubleshooting identified a broken fuse block connection in the EDG 3 auto-start circuitry, which would have prevented a Technical Specification (TS) required auto-start of EDG 3. This condition concurrent with EDG 1 out-of-service would have precluded emergency power supply to emergency busses needed to mitigate the consequences of an accident.</br>Technical Specification 3.8.1, Required Action D.3, requires declaring the required features supported by the inoperable EDG 3 inoperable when the redundant required features are inoperable. As a result, both required Conventional Service Water (CSW) pumps were declared inoperable at 1635 EST on March 4, 2016. This also required declaring both Control Building Instrument Air Compressors inoperable. As a result, both Control Room Emergency Ventilation (CREV) subsystems and all three Control Building Air Conditioners were declared inoperable at 1635 EST on March 4, 2016.</br>The above conditions are reportable under 10 CFR 50.72(b)(3)(v)(D), as an event or condition that could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident. </br>This event did not result in any adverse impact to the health and safety of the public.</br>The risk significance of this event is considered to be low. Both EDG 2 and EDG 4 were available and protected, along with the supplemental diesel generator and offsite electrical sources. Except for the periods of time for repair activities and post-repair testing, EDG 3 remained available via manual start. Actions were taken to protect other redundant safety systems and additional defense-in-depth was provided.</br>EDG 3 was restored to Operable status March 4, 2016 at 1834 EST and this has restored the safety functions of the above mentioned systems.</br>The licensee notified the NRC Resident Inspector.ensee notified the NRC Resident Inspector.
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00:00:00, 4 March 2016 +
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