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At 1515 (CDT) on March 17th 2016, Grand Gu … At 1515 (CDT) on March 17th 2016, Grand Gulf Nuclear Station received a valid actuation signal of the Division 2 Engineered Safety Feature (ESF) Load Shedding and Sequencing system. The actuation signal was most likely caused by a lightning strike to the offsite power source supplying this ESF bus. This caused a loss of the in service shutdown cooling system and associated system actuations.</br>Grand Gulf Nuclear Station (GGNS) was in Mode 5 at 85 (degrees) F coolant temperature. Reactor Cavity was flooded to High Water Level with a time to reach 200 (degrees) F of 7.5hrs. GGNS is conducting a planned refuel outage with core alterations in progress. Systems were aligned as follows:</br>Division 2 Diesel Generator was OPERABLE and the associated ESF bus aligned to transformer ESF12 (115KV Port Gibson offsite feeder). Residual Heat Removal (RHR) system 'B' was in service in shutdown cooling being supplied from this ESF bus (16AB) with Alternate Decay Heat Removal available as a backup.</br>Division 3 Diesel Generator was unavailable due to planned maintenance on support systems. The associated ESF bus was also aligned to transformer ESF12 (115KV Port Gibson offsite feeder).</br>Division 1 Diesel Generator was available and the associated ESF bus aligned to the transformer ESF 11 (Switchyard offsite power feeders Baxter-Wilson and Franklin). Power was never lost to this bus. RHR 'A' and Low Pressure Core Spray (LPCS) were not available due to planned maintenance (tagged out of service).</br>ESF 21 Transformer was out of service for planned maintenance.</br>A suspected lightning strike caused a momentary perturbation in power in the 115KV Port Gibson line causing the Division 2 Load Shedding and Sequencing (LSS) system to actuate. This actuation caused a loss of Residual Heat Removal system 'B' due to being shed (expected). The Division 2 Diesel Generator started and tied onto the bus as expected, restoring power in 7 seconds. Shutdown cooling was restored at 1518 (CDT) and was out of service for 3 mins 13 sec. Reactor coolant and spent fuel pool temperatures remained at 85 (degrees) F throughout this scenario. Core Alterations were suspended and fuel placed in its designated location per the approved movement plan. Division 3 systems; High Pressure Core Spray, Standby Service Water System 'C', and Division 3 Diesel Generator were tagged out of service for planned maintenance. Division 3 Diesel Generator received a valid actuation signal but did not start due to being out of service. The Division 3 bus was restored manually to ESF 11.</br>All safety systems operated as expected for the loss of power to ESF 12 and Division 2 LSS actuation.</br>This is being reported under:</br>1. 10CFR50.72(b)(3)(iv)(A)-Specified system actuation; Division 2 LSS and Division 3 Diesel Generator start logic.</br>2. 10CFR50.72(b)(3)(v)(B)-RHR Capability; Loss of shutdown cooling.</br>The NRC Resident Inspector has been notified. NRC Resident Inspector has been notified.
20:15:00, 17 March 2016 +
51,800 +
23:15:00, 17 March 2016 +
20:15:00, 17 March 2016 +
At 1515 (CDT) on March 17th 2016, Grand Gu … At 1515 (CDT) on March 17th 2016, Grand Gulf Nuclear Station received a valid actuation signal of the Division 2 Engineered Safety Feature (ESF) Load Shedding and Sequencing system. The actuation signal was most likely caused by a lightning strike to the offsite power source supplying this ESF bus. This caused a loss of the in service shutdown cooling system and associated system actuations.</br>Grand Gulf Nuclear Station (GGNS) was in Mode 5 at 85 (degrees) F coolant temperature. Reactor Cavity was flooded to High Water Level with a time to reach 200 (degrees) F of 7.5hrs. GGNS is conducting a planned refuel outage with core alterations in progress. Systems were aligned as follows:</br>Division 2 Diesel Generator was OPERABLE and the associated ESF bus aligned to transformer ESF12 (115KV Port Gibson offsite feeder). Residual Heat Removal (RHR) system 'B' was in service in shutdown cooling being supplied from this ESF bus (16AB) with Alternate Decay Heat Removal available as a backup.</br>Division 3 Diesel Generator was unavailable due to planned maintenance on support systems. The associated ESF bus was also aligned to transformer ESF12 (115KV Port Gibson offsite feeder).</br>Division 1 Diesel Generator was available and the associated ESF bus aligned to the transformer ESF 11 (Switchyard offsite power feeders Baxter-Wilson and Franklin). Power was never lost to this bus. RHR 'A' and Low Pressure Core Spray (LPCS) were not available due to planned maintenance (tagged out of service).</br>ESF 21 Transformer was out of service for planned maintenance.</br>A suspected lightning strike caused a momentary perturbation in power in the 115KV Port Gibson line causing the Division 2 Load Shedding and Sequencing (LSS) system to actuate. This actuation caused a loss of Residual Heat Removal system 'B' due to being shed (expected). The Division 2 Diesel Generator started and tied onto the bus as expected, restoring power in 7 seconds. Shutdown cooling was restored at 1518 (CDT) and was out of service for 3 mins 13 sec. Reactor coolant and spent fuel pool temperatures remained at 85 (degrees) F throughout this scenario. Core Alterations were suspended and fuel placed in its designated location per the approved movement plan. Division 3 systems; High Pressure Core Spray, Standby Service Water System 'C', and Division 3 Diesel Generator were tagged out of service for planned maintenance. Division 3 Diesel Generator received a valid actuation signal but did not start due to being out of service. The Division 3 bus was restored manually to ESF 11.</br>All safety systems operated as expected for the loss of power to ESF 12 and Division 2 LSS actuation.</br>This is being reported under:</br>1. 10CFR50.72(b)(3)(iv)(A)-Specified system actuation; Division 2 LSS and Division 3 Diesel Generator start logic.</br>2. 10CFR50.72(b)(3)(v)(B)-RHR Capability; Loss of shutdown cooling.</br>The NRC Resident Inspector has been notified. NRC Resident Inspector has been notified.
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