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| Entered date | Event description | |
|---|---|---|
| ENS 48828 | 18 March 2013 18:00:00 | On March 18, 2013, at approximately 1605 CDT, the station commenced notification of the Louisiana Department of Environmental Quality and other offsite governmental agencies that traces of radioactive contaminants were found at the site of an underground pipe leak on station property. This leak could potentially contain tritium and cobalt-60, and is believed to have been contained on the plant site. The leakage path has been isolated. The station is currently starting up following a refueling outage. In October 2012, water was found leaking from the ground and accumulating in a ditch near the station's sewage treatment plant. The initial investigation concluded that the source of the leak was domestic water, based on pH sample results, known buried piping in the area, and the fact that the sewage treatment plant operates intermittently. During the recent refueling outage, which started on February 16, it was noted that the leak had stopped. Testing of the potentially affected piping found that the leak was not domestic water, but was actually coming from the sewage treatment plant effluent line. It was determined that the constant leakage seen in October 2012 was due to a failed check valve in the effluent line. This check valve is designed to prevent backflow from the main condenser circulating water system blow-down line. The failed check valve was allowing water from the blow-down line to flow backwards into the sewage plant effluent line and out of the breach. The leak had stopped because the circulating water system blow-down line was shut down at the start of the refueling outage. Discharges from the liquid radwaste system also flow into the blow-down line at a point upstream of the connection to the sewage plant effluent line. During planned discharge of liquid radwaste, some of the diluted radioactive water was thus able to leak out on the ground. Samples of the dirt in the area of the leak obtained on March 17 found detectable levels of cobalt 60. No water is available to perform tritium analysis. This event is being reported in accordance with 10 CFR 50.72(b)(2)(xi) as a condition requiring notifications to local and state governmental agencies in accordance with the NEI 07-07 Industry Ground Water Protection Initiative. The leak path has been isolated. The licensee notified the NRC Resident Inspector. |
| ENS 48785 | 26 February 2013 16:59:00 | On February 25, 2013 at approximately 1030 CST, plant personnel discovered that a sump within a concrete berm area adjoining the condensate storage tank was overflowing. Water from the sump was entering an open excavation within the berm, and was soaking into the dirt underneath. At approximately 1400 (CST) that day, the sump level was pumped down to terminate the overflow. A portable tank has been staged in the area should any further pumping be required. Analysis of the water within the berm found tritium activity of 1.135 million picocuries per liter. Additionally, total gamma activity of 1.145 E-6 microcuries per milliliter was present in the sample. The estimated volume of water reaching the open excavation was approximately 380 gallons. Notification of this event has been made to local and state governmental agencies in accordance with NEI 07-07, Industry Ground Water Protection Initiative. The initial notifications were made at approximately 1430 CST today. This event is being reported in accordance with 10CFR50.72(b)(2)(xi) as a condition for which local and state governmental agencies have been notified. The station has also notified the NRC Resident Inspector, as well as NRC Region 4 personnel. |
| ENS 47541 | 21 December 2011 11:52:00 | On Tuesday, December 20, 2011, technicians discovered detectable levels of tritium in an onsite groundwater well. The measured concentration of the isotope was approximately 48,000 picocuries per liter. This discovery was made during the conduct of the site's ongoing groundwater monitoring program. The tritium concentration in the well sample exceeds the EPA established threshold for drinking water of 20,000 picocuries per liter. However, no groundwater wells on the River Bend site are used for drinking water. There has been no tritium identified in any wells downstream of, or surrounding, the affected well. This test result does not indicate any threat to public health or safety, since the affected well is only used for groundwater monitoring, and not drinking water. Other onsite wells in the area were tested and will continue to be tested to ensure the tritium is not migrating offsite. The monitoring of the wells in the area immediately surrounding the affected well will be increased to a monthly frequency. Voluntary notification of this discovery has been made to local and state governmental agencies, with the initial notification being made at 0930 CST today. This event is being voluntarily reported in accordance with 10CFR50.72(b)(2)(xi) as a condition related to health and safety of the public and onsite personnel for which a news release is planned. The licensee has notified the NRC Resident Inspector, state and local agencies and will be releasing information to the media.
On August 7, 2012, one of the six new groundwater monitoring wells installed near the monitoring well which yielded the positive results on December 20, 2011, produced a groundwater sample containing 432,733 picocuries per liter of tritium. The investigation of the groundwater tritium activity is still ongoing, and the installation of these wells is part of that effort to determine the source. The NRC Resident Inspector has been notified and officials with the Louisiana Department of Environmental Quality will be briefed. Notified R4DO (Michael Vasquez) |
| ENS 46844 | 12 May 2011 11:29:00 | On March 20, 2011, at approximately 7:24 a.m. CDT, the 'A' reactor protection system (RPS) bus was unexpectedly de-energized. Plant systems responded as designed, resulting in a half-scram signal and the actuation of the Division 1 primary containment isolation sub-system. The Division 1 primary containment isolation valves closed in several balance-of-plant systems. After confirming that no valid RPS trip signal had occurred, operators executed the appropriate procedures to return the affected systems to the proper configuration, and to reset the half-scram signal. Plant capacity was not affected by this event. This event is being reported in accordance with 10CFR50.73(a)(1) as an automatic actuation of the Division 1 primary containment isolation valves in multiple systems resulting from an invalid signal. Each of the two redundant distribution buses in the RPS system is normally powered by its own motor-generator (MG) set. The investigation of this event determined that the output breaker of the 'A' MG set had tripped open. The most likely cause for this trip was a malfunction of the over-voltage relay circuit card in the MG set. Although the troubleshooting was inconclusive, there apparently was a momentary transient in the output of the trip setpoint adjustment potentiometer on the card, likely caused by oxidation on the contacting surface between the wiper arm and the windings. The over-voltage relay card on the 'A' MG set was replaced, and the unit was restored to service. Preventative maintenance tasks are being revised to periodically cycle all potentiometers in the MG set control circuits to wipe oxidation from the windings. The Licensee has notified the NRC Resident Inspector. |
| ENS 43012 | 27 November 2006 10:35:00 | On September 29, 2006, at 1:33 pm CDT, a safety-related 120VAC distribution panel was inadvertently de-energized during a planned shift of its power supply. The plant was operating at 100 percent power at the time. The loss of power resulted in the automatic closure of primary containment isolation valves in the reactor water cleanup and the suppression pool cooling/cleanup systems. This event is being reported in accordance with 10CFR50.73(a)(1) as an invalid actuation of the containment isolation valves affecting more than one system. This event occurred during a planned shift of the inverters that supply the distribution panel. This shift was being performed to support post-maintenance testing of one of the inverters. The operators performing the shift were utilizing the appropriate procedure. At a certain point in the procedure, the off-going inverter was deenergized, and the operators discussed the expected equipment response. Following that discussion, a step was erroneously performed out of sequence, resulting in the loss of power to the 120VAC distribution panel. The primary containment isolation signal was actuated as designed, and the appropriate valves responded correctly. Reactor power was not affected by the containment isolation signal. The pertinent response procedures were implemented, and actions were taken to restore the distribution panel to service. This was completed at 5:31 pm CDT that day. The licensee will notify the NRC Resident Inspector. |
| ENS 41082 | 1 October 2004 12:00:00 | At 7:30 a.m. (CDT) on October 1, 2004, an automatic reactor scram occurred as a result of an electrical fault on the main generator output lines that caused a main generator trip and turbine trip. All control rods inserted. Approximately 13 minutes prior to the fault, a loss of one station service transformer had occurred. This resulted in an automatic start of the Division 1 diesel generator and a loss of power to some plant auxiliaries, including the feedwater level regulation isolation valves. The loss of reserve station service no. 1, combined with the trip of the main generator, caused a loss of power to two condensate pumps and one main feedwater pump. The remaining two feedwater pumps tripped on low suction pressure. The reactor containment isolation cooling pump (RCIC) steam supply isolated during the scram transient, so the control room operators manually started the high-pressure core spray system (HPCS) pump for level control. The injection valve was closed as level had already reached the high water level isolation setpoint for that valve. It was later reopened manually as level approached the low level setpoint (level 2), which would have automatically opened the valve. The level 2 setpoint was reached briefly after the valve was already open. Reactor pressure is being controlled manually with safety relief valves (SRV's). The main steam isolation valves (MSIV's) were manually closed due to lowering pressure from steam loads in the plant that could not be immediately isolated because of loss of power to their valves. RCIC is also running in CST (condensate storage tank) to CST mode, to augment pressure control. The electrical load center which supplies power to the instrumentation and valves needed for feedwater operation was cross-tied to an alternate power source, and feedwater was restored to operation and is presently controlling reactor water level. During the event, standby service water also initiated. This is the presently known information. Further information will be provided as the investigation continues. The licensee has notified the NRC Resident Inspector. |
| ENS 40847 | 30 June 2004 11:00:00 | The following information was received from the licensee via facsimile: On May 22, 2004, at approximately 4:29 am EDT, while the plant was operating at 100% power, the normal power supply to the Division 1 Reactor Protection System (RPS) bus was lost. This caused the actuation of the Division 1 primary containment isolation logic circuit. This was an event that resulted in the actuation of a general containment isolation signal affecting more than one system. However, as this event meets the definition of an invalid actuation (i.e., not a response to an actual plant parameter exceeding a trip setpoint), this notification is being made in accordance with 10CFR50.73(a)(1) in lieu of a Licensee Event Report. Operators implemented the applicable response procedures, and shifted Division 1 RPS to its alternate power supply. The containment isolation signal was reset, and systems were restored to normal alignment. Reactor power was not affected by this event. All safety related equipment controlled by the affected circuits responded to the loss of Division 1 RPS as required, with one exception. The Division 1 control building emergency filtration train should have automatically initiated, but did not. Subsequent troubleshooting discovered a failed relay in its control circuitry. This defect would not have prevented the Division 2 control building emergency filtration train from performing its safety function. It was determined that a relay coil in the control circuitry for the Division 1 RPS motor-generator set failed. This caused the main output contactor on the MG set to open, interrupting power to the bus. Repairs were completed on June 3, 2004, and the Division 1 RPS bus was then shifted back to its normal power supply. The licensee has notified the NRC Resident Inspector of this notification. |