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| Entered date | Event description | |
|---|---|---|
| ENS 49920 | 17 March 2014 09:25:00 | On 3/17/2014 at 0514 (CDT) the reactor was manually scrammed from approximately 41% core thermal power due to a steam leak in the turbine building. All control rods fully inserted and all systems actuated and operated as designed. All Main Steam Isolation Valves were manually shut. The Reactor Core Isolation Cooling System was manually initiated to assist in level control and pressure control. No safety relief valves actuated automatically. Manual cycling of safety relief valves and Reactor Core Isolation Cooling are being used to maintain reactor water level and pressure within normal bands. Group 2 and 3 RHR isolation signals were received; however no valve movement occurred since the affected valves are normally closed. This event is reportable under 10CFR50.72(b)(2)(iv)(B) for the reactor trip and 50.72(b)(3)(iv)(A) for the manual start of the reactor core isolation cooling system. The licensee informed the NRC Resident Inspector. |
| ENS 48133 | 25 July 2012 17:32:00 | During annual physical inventory of Special Nuclear Material (SNM) conducted at Grand Gulf Nuclear Station (GGNS), a replacement Source Range Monitor (SRM) detector could not be accounted for. The SRM detector was being stored in the refuel floor storage locker after maintenance activities during RF18. This detector did not function and was removed prior to the start-up therefore, the SRM detector was not subjected to a critical reactor. Actions continue to locate the missing SRM detector. There is no evidence of sabotage or tampering associated with this activity. The licensee notified the NRC Resident Inspector. Sources that are "Less than IAEA Category 3 sources," are either sources that are very unlikely to cause permanent injury to individuals or contain a very small amount of radioactive material that would not cause any permanent injury. Some of these sources, such as moisture density gauges or thickness gauges that are Category 4, the amount of unshielded radioactive material, if not safely managed or securely protected, could possibly - although it is unlikely - temporarily injure someone who handled it or were otherwise in contact with it, or who were close to it for a period of many weeks. For additional information go to http://www-pub.iaea.org/MTCD/publications/PDF/Pub1227_web.pdf This source is not amongst those sources or devices identified by the IAEA Code of Conduct for the Safety & Security of Radioactive Sources to be of concern from a radiological standpoint. Therefore is it being categorized as a less than Category 3 source |
| ENS 47798 | 2 April 2012 22:56:00 | 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. |
| ENS 47679 | 19 February 2012 22:00:00 | On 2/19/2012 at 1904 hrs (CST) the reactor was manually scrammed from approximately 23% core thermal power due to lowering reactor water level. All control rods fully inserted and all systems actuated and operated as designed. The Reactor Core Isolation Cooling System was manually initiated to assist in level control. No safety relief valves actuated. Reactor level and pressure are currently being controlled within normal bands. Group 2 and 3 RHR Isolation signals were received, however no valve movement occurred since the affected valves are normally closed. This event is reportable under 10CFR50.72(b)(2)(iv)(B) for the reactor trip and 50.72(b)(iv)(A) for the manual start of the core isolation cooling system. The lowest Reactor Vessel Water Level (RVWL) observed was -38 inches WR (Wide Range). RVWL was restored by placing the "A" Reactor Feed Pump (RFP) in service. The "B" RFP which had been operating was secured for troubleshooting. The Unit was in the process of shutting down for its scheduled Refueling Outage #18. The NRC Resident Inspector was in the control room at the time of the transient. |
| ENS 46802 | 29 April 2011 12:42:00 | On 4/28/2011, Grand Gulf Nuclear Station Unit 2 turbine building sump samples indicated tritium presence. The Unit 2 turbine building is an abandoned, partially constructed building. Follow-up review and investigation confirmed that water from Unit 2 turbine building sump had been pumped to the environment through installed sump pumps and piping connected between the sumps and roof drains on the Unit 2 turbine building. The release has been terminated by turning off the sump pumps located in the Unit 2 turbine building. Site procedures require notification of off-site agencies, therefore the NRC is being notified in accordance with 10 CFR 50.72(b)(2)(xi). The NRC Resident Inspector has been informed. The state will be informed. |
| ENS 44595 | 23 October 2008 11:44:00 | 'A' Reactor Feed Pump speed decreased to zero with no trip signal evident in the Control Room for the 'A' Reactor Feed Pump. The reactor scrammed due to loss of feedwater flow on a Level 3 (11.4") RPS scram signal as designed. Operators implemented appropriate off normal event procedures to mitigate the transient with all systems responding as designed. Lowest reactor water level observed was -35" wide range. All withdrawn control rods fully inserted to position '00'. The Reactor Core Isolation Cooling System was manually initiated and was used to restore water level to within the normal band. No ECCS initiations were received and all systems responded as designed. Additionally, no SRVs lifted as a result of this event. Level 3 is also a setpoint for Group 2 (RHR to Radwaste) and Group 3 (Shutdown Cooling Isolation) automatic isolation. No valves isolated in these systems due to them being in their normally CLOSED position prior to the event. Currently, reactor water level is being maintained by the condensate system in normal level band and reactor pressure is being controlled to limit cool down. The licensee has notified the NRC Resident Inspector. |
| ENS 43899 | 12 January 2008 20:57:00 | On 1/12/08 at 1626 hours a manual scram was inserted due to degraded cooling on the main transformers. All control rods fully inserted and all systems actuated and/or operated as designed. No safety relief valves opened during the event and reactor pressure is currently being controlled within normal bands with bypass valves. Reactor water level is also being controlled within normal bands with the condensate and feedwater system. Group 2 and 3 isolation signals were received however, no valve movement occurred since these valves are normally closed." The licensee is investigating a potential electrical fault which may have caused the event, but it appears that there was an electrical fault in the transformer cooling system. The grid is normal with no transmission system warnings in effect. All feeds are available. Reactor vessel level is 32.6 inches stable with normal condensate system feeding the vessel. Primary plant pressure is 815 psig. All safety and BOP electrical buses are energized normally. No bus power was lost. Decay heat path is via bypass valves to the main condenser. The licensee will notify the NRC Resident Inspector. |
| ENS 41589 | 11 April 2005 19:59:00 | A single Alert Notification System siren inadvertently sounded. The Clairborne Count Civil Defense Department is issuing a notification to local media advising the public of the inadvertent sounding and that no emergency exists. The siren has been secured. There were no effects on plant operations. The inadvertent siren actuation may have been due to bad weather in the area. The licensee has notified the NRC Resident Inspector. |
| ENS 40131 | 4 September 2003 04:18:00 | The following was received via fax from the licensee: Radiation protection technician passed away due to what appears to be a heart attack. On-site emergency medical attention was given and the individual was transported to a local hospital where he was pronounced dead. Although this event occurred on-site, the individual was not within the Controlled Access Area (CAA) and was not contaminated. The licensee made an offsite notification to the Occupational Safety & Health Administration (OSHA) and notified the NRC Resident Inspector. |