Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 53676 | 19 October 2018 21:44:00 | At 1725 CDT, a Feedwater Regulating valve failed closed, resulting in a reactor level transient, which initiated a reactor trip, Primary Containment Isolation System signals to valves in Groups 2, 3, and 4 and initiation of High Pressure Coolant Injection and Reactor Core Isolation Cooling. All control rods inserted and level has been restored to normal. The cause of the feedwater valve failure is under investigation. All other systems responded as expected. This report is being made under 10 CFR 50.72 (b)(2)(iv)(B), (b)(3)(iv)(A) and (b)(2)(iv)(A). The Senior Resident Inspector has been informed. Decay heat is being removed via the main condenser and reactor vessel water level is being maintained by the condensate and feedwater systems. |
| ENS 51697 | 29 January 2016 17:09:00 | At 0920 CST on 1/29/16, while performing main generator voltage adjustments at the direction of the transmission operator, Duane Arnold Energy Center (DAEC) switchyard voltage lowered to the calculated point where offsite sources were considered inoperable. During this event, both onsite emergency diesel generators were fully operable and capable of performing their intended safety function. While no safety concerns arose, Technical Specification (TS) Limiting Condition for Operability (LCO) 3.8.1.a Condition C was entered due to two offsite electric power circuits being inoperable. Immediate actions were taken to adjust main generator voltage to restore switchyard voltage. In less than 10 minutes, both offsite circuits were declared operable and LCO 3.8.1.a Condition C was exited. This resulted in a reportable event pursuant to 10CFR50.72(b)(3)(v)(D). During the time of reduced grid voltage, no bus low-voltage alarms nor any equipment issues occurred. The cause of this event is under investigation, and there are not any current operability concerns with the offsite power circuits. The licensee has notified the NRC Resident Inspector.
The purpose of this notification is to retract a previous report made on 1/29/16 at 1709 (EST). NRC notification was initially made as a result of offsite power sources being declared inoperable due to the identification of a low voltage condition by the grid operator. Subsequent to the initial report, NextEra Energy Duane Arnold (NextEra) has determined that the offsite power grid conditions were above the required limit and were therefore operable. It was determined that a trip of the DAEC turbine/generator would not have led to fluctuations in voltages in the DAEC switchyard below the trip setpoints for Loss of Power. Based on this, the safety-related buses and loads were fully capable of performing their intended design basis function. The degraded voltage relays setpoint were not reached; therefore, the essential electrical buses remained connected to offsite power. Therefore, the low voltage condition does not meet the reporting requirements of 10 CFR 50.72 or 10 CFR 50.73 The Resident Inspector has been notified. Notified R3DO (Kozak). |
| ENS 50891 | 13 March 2015 18:59:00 | This condition is reported in accordance with 10 CFR 50.72(b)(3)(v). On 3/12/15, during surveillance testing on LPCI (Low Pressure Coolant Injection) Loop Select Instrumentation, a degraded component was discovered. At 1230 CDT on 3/13/15, LPCI was declared INOPERABLE in accordance with Technical Specification requirements. All remaining ECCS systems remain available and operable. The NRC Resident Inspector has been informed.
At 0105 CDT on 3/14/15, the subject component has been replaced and retested with satisfactory results. LPCI INOPERABLE condition was exited at 0105 CDT and the LPCI System is OPERABLE. The licensee informed the NRC Resident Inspector. Notified R3DO (Orth).
The purpose of this notification is to retract a previous report made on 3/13/15 at 1859 EDT. Notification of the event to the NRC was initially made as a result of an event where Low Pressure Coolant Injection (LPCI) was declared inoperable due to the discovery of a degraded LPCI Loop Select timing relay. Subsequent to the initial report, NextEra Energy Duane Arnold (NextEra) has determined that the LPCI Loop Select timing relay was tested in a configuration that affected time delay measurements. This testing configuration was revised in 2012 following a modification to the LPCI Loop Select Logic, STP 3.3.5.1-29. The inadequate testing configuration adversely affected the time delay when the test equipment was installed. A revision to STP 3.3.5.1-29 was completed to resolve the inadequate testing configuration. Subsequent bench testing, performed to mimic plant installed configuration, of the affected relay, was completed. This testing demonstrated that the relay could be tested in a manner that provided acceptable results, and it has been concluded that the relay would have performed its required safety function up to when it was tested on 3/13/15. Therefore, this event is not considered a Safety System Functional Failure and is not reportable to the NRC as a Licensee Event Report (LER) per 10 CFR 50.73. The NRC Resident Inspector has been notified. Notified R3DO (Valos). |
| ENS 50154 | 30 May 2014 14:43:00 | At 1043 CDT, during an instrument test, the High Pressure Coolant Injection (HPCI) system isolated due to an invalid signal. The isolation was on the 'A' (inboard) logic, which rendered the HPCI system INOPERABLE. The isolation was received while instrument technicians were installing a relay block during the performance of Surveillance Test Procedure 3.3.6.1-43 'HPCI Steam Line High DP Instrument Channel Functional Test.' Operations Personnel have repressurized HPCI piping, installed the relay cover, and declared HPCI System OPERABLE at 1209 (CDT). This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(D) due to the failure of a single train system preventing accident mitigation. The NRC Resident Inspector has been informed. |
| ENS 50153 | 30 May 2014 14:43:00 | At 0759, on May 30, 2014, both doors in one of the Secondary Containment Airlocks were open concurrently. The doors being open at the same time caused a failure to meet SR 3.6.4.1.2 to verify that either the outer door(s) or the inner door(s) in each Secondary Containment access opening are closed. The identified condition caused Secondary Containment to be considered INOPERABLE per TS LCO 3.6.1.4. Upon discovery, immediate action was taken to close the doors. This action allowed SR 3.6.4.1.2 to be met, and restored Secondary Containment to OPERABLE status. This notification is being made pursuant to 10 CFR 50.72(b)(3)(v)(C). The NRC Resident Inspector has been notified. The cause of this event was a misaligned door magnet. |
| ENS 49557 | 19 November 2013 08:29:00 | A planned maintenance evolution at the Duane Arnold Energy Center (DAEC) will remove the emergency power supply to the TSC from service. The TSC would be rendered non-functional with the loss of normal power. The repair to the power supply is expected to last 1 day. If an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing emergency planning procedures. Maintenance will be expedited to restore the emergency power supply to service. This notification is being made in accordance with 10 CFR 50.72(b)(3)(xiii) due to the loss of an Emergency Response Facility (ERF). An update will be provided once the TSC emergency power supply has been restored to normal operation. The NRC Resident Inspector has been notified.
The emergency power has been returned to service to the TSC. The licensee has notified the NRC Resident Inspector. Notified R3DO (Hills). |
| ENS 48214 | 21 August 2012 06:14:00 | A planned maintenance evolution at the Duane Arnold Energy Center (DAEC) will remove the emergency power supply to the TSC from service. The TSC would be rendered non-functional with the loss of emergency power. The repair to the power supply is expected to last three days. If an emergency is declared requiring TSC activation during this period, the TSC will be staffed and activated using existing emergency planning procedures. Maintenance will be expedited to restore the emergency power supply to service. This notification is being made in accordance with 10CFR50.72(b)(3)(xiii) due to the loss of an Emergency Response Facility (ERF). An update will be provided once the TSC emergency power supply has been restored to normal operation. NRC Resident has been notified.
Maintenance has been completed on the TSC. The TSC has been returned to service. Notified R3DO (Duncan). |