Semantic search
Jump to navigation
Jump to search
| Entered date | Event description | |
|---|---|---|
| ENS 52908 | 15 August 2017 20:21:00 | A blind sample provided from an independent laboratory to fleet testing facility was returned with inaccurate results. This is in violation of 10 CFR 26.719(c)(3) and requires a 24-hour report. The licensee has notified the NRC Resident Inspector. |
| ENS 52897 | 10 August 2017 17:14:00 | A non licensed supervisor confirmed positive for alcohol during a fitness for duty test. The employee's access has been terminated. The NRC Resident Inspector has been notified. |
| ENS 52602 | 10 March 2017 11:41:00 | At 0714 CST on March 10, 2017, with the unit in Mode 1 at approximately 17% power, a manual actuation of the reactor protection system (RPS) was initiated due to rising reactor pressure caused by the closure of the Main Turbine Control Valves (MTCV's). The cause of the closure of the MTCV's is under investigation. The unit is currently stable in Mode 3. All control rods inserted as expected; water level control is stable in the normal control band and reactor pressure is being maintained with steam line drains (aligned to the main condenser). The NRC Senior Resident Inspector has been notified. |
| ENS 51754 | 24 February 2016 18:16:00 | At 1100 CST on February 24, 2016, with the plant in cold shutdown (Mode 4), the shift manager was notified of a condition that could potentially prevent the automatic closure of the circuit breakers powering the emergency ventilation fans in the both the Division 1 and 2 emergency diesel generator rooms. These fans are not in Technical Specifications, however, they provide a support function to the emergency diesel generators, requiring that both diesel generators to be declared inoperable. This inoperability constitutes a condition that could potentially prevent fulfillment of the safety function of onsite AC power sources, and is being reported pursuant to 10 CFR 50.72(b)(3)(v). Four additional breakers are affected by the same condition. These breakers supply power to Division 1 and 2 containment unit coolers and the Division 1 and 2 auxiliary building 141 ft. elevation general area unit coolers. The auxiliary building unit coolers are not in Technical Specifications, however, they provide a support function to the electrical distribution system. The Technical Specification required action is to declare both trains of the residual heat removal system (shutdown cooling mode) inoperable. This inoperability constitutes a condition that could potentially prevent the fulfillment of the decay heat removal safety function, and is being reported pursuant to 10 CFR 50.72(b)(3)(v). Division 2 residual heat removal is operating in shutdown cooling, satisfactorily maintaining reactor coolant temperature. The affected breakers can be manually operated to start/stop their associated equipment, if necessary for operation. This condition was identified during an Engineering review. The licensee has compensatory measures in place. Long term corrective actions are under review. The licensee informed the NRC Resident Inspector. |
| ENS 51599 | 11 December 2015 02:30:00 | On August 1, 2015, during tagging activities to support planned maintenance on a condensate demineralizer, operators incorrectly positioned certain air-operated components which, combined with apparent leakage past a solenoid valve, resulted in a drain opening on a demineralizer that was in service. Flow through the drain line caused a turbine building sump to overflow to the floor of the 67 foot elevation of the Turbine Building. Immediate actions were taken to stop the leak. The spill volume was approximately 60,000 gallons of condensate. The tritium activity of the water is estimated at 1.32E-2 microCi/ml. Gamma activity was from noble gases only in a concentration of approximately 2.30E-6 microCi/ml. The spill was confined to the Turbine Building. The affected area contains degraded floor seals which might allow the spill to reach groundwater. The reason for this notification is that industry and governmental officials were notified of this event on August 3, 2015. The NRC Senior Resident Inspector was notified and informal notification was made to the NRC Region IV office, the Louisiana Department of Environmental Quality, and West Feliciana Parish government authorities. The Nuclear Energy Institute was informed as specified in their ground water protection initiative. Plant cleanup activities arising from the spill are complete. |
| ENS 51112 | 2 June 2015 02:00:00 | At 2111 (CDT) River Bend Nuclear Station sustained an Automatic Reactor Scram due to low Reactor Water Level (Level 3). The plant is currently stable, with level being maintained in a normal band of 10 - 51 inches with Condensate and Feedwater. Reactor Pressure is in the prescribed band of 500-1090 psig. The plant is in Mode 3, Hot Shutdown, and will remain in Mode 3 until investigation of the scram is complete. The transient began with a trip of Reactor Feed Pump 'A', followed by a Reactor Scram and a trip of Reactor Feed Pump 'C'. Reactor water level was recovered with Reactor Feed Pump 'B' to a normal post scram level band. There was a problem noted with the Reactor Feedwater Master Level Controller; this was mitigated by the Operator placing the controller to manual. There was no subsequent Level transient. Reactor Pressure was stabilized in normal pressure band with Turbine bypass valves. During the transient, a Reactor Recirculating Flow Control Valve Runback was not received as expected. Reactor Recirculating Pump 'A' responded as expected to transient (switching to low pump speed), Reactor Recirculating Pump 'B' tripped during transient. A Level 3 isolation signal was received, all expected isolations occurred. The cause of the transient is currently under investigation. The reactor is stable in Mode 3 with decay heat being removed via turbine bypass valves, and a normal electrical line up. The NRC Resident Inspector has been notified.
At 2231 on 6/1/15, Reactor Water Cleanup System isolated on High Reactor Water Cleanup System Heat Exchanger room temperature due to loss of Turbine Building chill water during the initial transient. All Reactor Water Cleanup System Valves isolated as expected. Reactor Water Cleanup was the only system affected by this isolation signal. The licensee has notified the NRC Resident Inspector. Notified R4DO (Whitten). |
| ENS 51083 | 21 May 2015 12:03:00 | At 0309 CDT on May 21, 2015, with the plant operating at 100 percent power, the shift manager was notified of a condition that could potentially lead to the failure of safety-related inverters in the DC electrical distribution system. This condition was identified while reviewing completed probabilistic risk analysis (PRA) calculations. It was discovered that control building ventilation system heat load calculations were not updated when new AC/DC inverters, with significantly higher heat output, were installed in 2007. Since the heat load calculations were not updated, it was not realized at the time that, under post-accident conditions involving a specific single failure, the DC electrical equipment rooms (i.e., inverters and battery chargers) could exceed their design basis ambient temperature, potentially leading to the failure of the inverters or battery chargers, and the loss of DC power in both divisions of the distribution system. The postulated scenario is the loss of offsite power (LOP)/loss of coolant accident (LOCA), followed by the failure of a single emergency diesel generator. If within 20 minutes prior to the onset of the event, the control building ventilation system had been shifted to the division in which the emergency diesel generator successfully started, the chiller in that division would, by design, be prevented from re-starting for as much as 20 minutes by its anti-recycle feature. (That feature limits successive starts of a chiller to prevent over-heating the motor.) The other chiller in that same division must be manually aligned for service, so it is not assumed to be available for these purposes. During the period in which the anti-recycle timer is running, no chiller would be in service, and the actual heatup rate of the inverters/battery charger could lead to room temperatures in excess of their design basis assumptions. As stated above, this condition (no ventilation cooling) would only exist for a maximum of 20 minutes from the time the associated divisional chiller was started, concurrent with a LOP/LOCA and a single failure. After expiration of the 20 minute timer, the chiller would perform the required function and lower room temperatures as expected. For best estimate PRA purposes, River Bend assumes an equipment survivability criteria of exposure to temperatures above 122 degrees F, but below 150 degrees F, for up to four hours. This is based upon the industry Station Blackout guidance of NUMARC 87-00, which was endorsed by the NRC as the basis for industry response to the Station Blackout Rule. This condition exists only after planned chiller swap and can be mitigated by opening the door to the inverter room should a LOP/ LOCA occur prior to the expiration of the 20 minute timer. Measures are in place for a dedicated operator to perform this function pending a modification to resolve the issue. This condition is being reported in accordance with 10 CFR 50.72(b)(3)(v) as the potential loss of the safety function of the DC electrical distribution system. The licensee has notified the NRC Resident Inspector. |
| ENS 50324 | 30 July 2014 13:27:00 | On July 30, 2014, at (0940 CDT), with the plant operating at 100% power, a review of an engineering analysis of the ultimate heat sink (UHS) determined that the UHS had been in an unanalyzed condition that degraded plant safety. This condition was the result of a design basis deficiency for the UHS that did not account for the adverse effects of system leakage on compliance with the 30-day inventory required by Regulatory Guide 1.27. The system design basis requires that 30-day inventory be maintained, with the assumption that no replenishment of the UHS occurs for the entire duration of the postulated event. In support of the development of the engineering analysis, compensatory measures have been implemented which provide adequate assurance that the UHS will perform its design safety function. Corrective actions to restore full compliance with design basis requirements are in development. This event is being reported in accordance with 10 CFR 50.72 (b)(3)(ii) as an unanalyzed condition that degraded the safety function of the UHS. The licensee notified the NRC Resident Inspector. |