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At 1039 CDT the reactor was manually (scrammed) due to a partial loss of plant service water. The loss of plant service water was caused by a loss of (balance of plant) BOP transformer 23. Reactor power was reduced in an attempt to restore pressure to plant service water. Reactor level is being maintained with condensate and feedwater. Reactor pressure is being maintained with bypass control valves. Standby Service Water A and B were manually initiated to supply cooling to Control Room A/C and (Engineered Safety Feature) ESF switchgear room coolers. The cause is under investigation. The NRC Resident Inspector has been notified. This event is being reported under 10 CFR 50.72(b)(2)(iv)(B) as any event or condition that results in actuation of the Reactor Protection System (RPS), when the reactor is critical and also reported under 10 CFR 50.72(b)(3)(iv)(A), as any event or condition that results in actuation of RPS and Standby Service Water. The plant is currently in a normal electrical lineup.

• * * UPDATE ON 5/12/19 AT 1846 EDT FROM GERRY ELLIS TO JEFFREY WHITED * * *

This is an update to the original notification. The Drywell and Containment exceeded the technical specification (TS) temperature limits of 135 degrees F (TS Limiting Condition of Operation (LCO) 3.6.5.5) and 95 degrees F (TS LCO 3.6.1.5), respectively. An 8-hour notification is being added for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material per 10 CFR 50.72(b)(3)(v)(C). Notified R4DO (Alexander).

EN Revision Text: MANUAL REACTOR SCRAM DUE TO FAILED OPEN TURBINE BYPASS VALVE At 1351 CST, the reactor was manually shutdown due to 'A' Turbine Bypass Valve opening. The Main Steam Line Isolation Valves were manually closed to facilitate reactor pressure control. Reactor level is being maintained through the use of Reactor Core Isolation Cooling System, Control Rod Drive System, and High Pressure Core Spray System. High Pressure Core Spray System was manually started to initially support reactor water level control. Reactor Pressure is being controlled through the use of the Safety Relief Valves and the Reactor Core Isolation Cooling System. The plant is stable in MODE 3. The cause of the 'A' Turbine Bypass Valve opening is under investigation at this time. The NRC Resident Inspector has been notified.

• * * UPDATE ON 12/14/18 AT 1140 EST FROM GERRY ELLIS TO TOM KENDZIA * * *

This is an update to EN # 53788 to correct an error on the event classification block of the form. The original notification did not have the block for 8 hour notification for Specified System Actuation checked. The actuation of Reactor Core Isolation Cooling System was discussed in original notification. The licensee notified the NRC Resident Inspector. Notified R4DO (Taylor).

At 0238 (CST) a manual reactor scram was inserted by placing the Reactor Mode Switch in Shutdown. At 0149 (CST), with reactor power just above the point of adding heat, IRM (Intermediate Range Monitor) channels A, C, and D received a spurious upscale trip signal which immediately cleared. Upon investigation, operability of RPS (Reactor Protection System) scram function for Intermediate Range Detectors was placed in question. This event is being reported under 10 CFR 50.72(b)(2)(iv)(B), as any event or condition that results in actuation of the Reactor Protection System (RPS), when the reactor is critical. The licensee notified the NRC Resident Inspector.

• * * UPDATE ON NOVEMBER 26, 2017, AT 1850 FROM GRAND GULF TO MICHAEL BLOODGOOD * * *

At 0238 (CST) a manual reactor scram was inserted by placing the Reactor Mode Switch in Shutdown. At 0149 (CST), with reactor power just above the point of adding heat, Intermediate Range Monitor neutron flux detector (IRM) channels A, C, and D received a spurious Upscale Trip signal which immediately cleared. Upon investigation, IRM channels A, C, and D were declared Inoperable. IRM G was already Inoperable for another reason. RPS scram function from IRM channels B, E, F, and H was always Operable and available. That event is being reported under 10CFR 50.72(b)(2)(iv)(B), as any event or condition that results in actuation of the Reactor Protection System (RPS), when the reactor is critical. This Revised Statement to Event Notification # 53090 is being made to make it clear that only four IRM channels (A, C, D, G) were Inoperable and that the IRM RPS SCRAM function was still available from the four remaining Operable IRM channels (B, E, F, and H). The licensee notified the NRC Resident Inspector. Notified R4DO (O'Keefe)

• * * RETRACTION ON 01/16/2018 AT 1629 EST FROM JASON COMFORT TO DAVID AIRD * * *

On 11/25/17, at 0149 (CST), with reactor power just above the point of adding heat, Intermediate Range Monitor neutron flux detector (IRM) channels A, C, and D received a spurious Upscale Trip signal which immediately cleared. Upon investigation, IRM channels A, C, and D were declared Inoperable. IRM G was already Inoperable for another reason. At 0238 (CST) a manual reactor scram was inserted by placing the Reactor Mode Switch in Shutdown. RPS scram function from IRM channels B, E, F, and H was always Operable and available. That event was initially being reported under 10 CFR 50.72(b)(2)(iv)(B), as any event or condition that results in actuation of the Reactor Protection System (RPS), when the reactor is critical. After the trip alarms were received, the Operators spent approximately twenty minutes investigating possible causes and implications, and consulted with Reactor Engineering and the Shift Technical Advisor. The investigation showed that the plant was stable and the upscale IRM alarms were spurious. A review of plant technical specifications by the operators determined that a plant shutdown was not required. After further discussions, Operations concluded that a shutdown to allow further investigation of the issue was the prudent course of action. Prior to shutting down, Operations spent approximately twenty minutes reviewing procedures, notifying personnel to exit containment, and conducting a brief. The shutdown was then conducted by inserting a manual reactor scram by placing the reactor mode switch in SHUTDOWN. This was initially reported under 10 CFR 50.72(b)(2)(iv)(B) as an actuation of the RPS. Based on the sequence of events, and Operator actions in conducting the shutdown, the event is considered 'part of a pre-planned sequence during testing or reactor operation' as specified in 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.73(a)(2)(iv)(A). In accordance with NUREG-1022, Section 3.2.6, the event is not reportable as an actuation of RPS. The licensee notified the NRC Resident Inspector. Notified R4DO (Taylor).

Actuation of Reactor Protection System with reactor critical. Reactor Scram occurred at 1432 CDT on 7/30/2013 from 100% Power. The cause of the scram appears to be a Turbine Generator trip. 05-S-01-EP-2, 'Reactor Pressure Vessel Control,' 05-1-02-I-1, 'Reactor Scram Off Normal Event Procedure,' and 05-1-02-I-2, 'Turbine and Generator Trip Off Normal Event Procedure,' were entered to mitigate the transient. No Loss of Off-site Power occurred. No Emergency Core Cooling System or Diesel Generator initiation occurred. Reactor Core Isolation Cooling initiated and injected. The lowest reactor water level reached was -36 inches wide range (RCIC initiation set point is -41.6 inches wide range). Main Steam Isolation Valves remained open and no Safety Relief Valves actuated. Currently, Main Turbine Bypass valves are controlling reactor pressure to the Main Condenser and Condensate and Feedwater is controlling reactor water level in the normal band and removing decay heat. There are no challenges to Primary or Secondary Containment. The NRC Senior Resident Inspector was notified.

* * * UPDATE FROM CHRIS ROBINSON TO PETE SNYDER AT 1841 EDT ON 7/30/13 * * * 

The first out recorder indicated that RPS actuation signal was due to high reactor pressure as a result of the turbine control valves going shut. Notified R4DO (Farnholtz).

On 4/2/12 at 1511 (CDT), GGNS (Grand Gulf Nuclear Generating Station) received a valid ESF actuation for emergency AC power to Division 3 4160V bus due to degraded voltage.

One of the two 500KV offsite feeders (Tech Spec Offsite Power Source) tripped causing a drop in grid voltage which resulted in a trip of the ESF feeder breaker for 4160 Volt Division 3 bus. The HPCS (High Pressure Core Spray) Diesel Generator automatically started and energized the bus. The HPCS system was not running and no ECCS initiation occurred during this event. The plant was in Mode 5 with RHR A in shutdown cooling. Divisions 1 and 2 ESF power monitoring instrumentation responded to the grid voltage transient but no actuation setpoints were reached. Division 1 and 2 ESF 4160V buses remained energized and shutdown cooling remained in service. The 500KV offsite feeder (Tech Spec Offsite Power Source) and additional 115 KV feeder (Tech Spec Offsite Power Source) remained in service. The 500KV feeder that tripped was restored by the dispatcher at approximately 1515 CDT. The Division 3 bus was subsequently transferred back to offsite power and the HPCS Diesel Generator was secured. This event is reportable per 10 CFR 50.72(b)(3)(iv). A lightning strike resulted in a voltage transient on the GGNS electrical distribution system. Due to this transient, the 'A' Control Room Air Conditioning Unit (CRAC 'A') tripped and had to be manually restarted. CRAC 'A' was not running for approximately two minutes. During this timeframe CRAC 'B' was tagged out of service. This was evaluated and determined to not be a loss of safety function. The licensee has notified the NRC Resident Inspector.