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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 52767 | 24 March 2017 18:25:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid System Actuation During Testing | On March 24, 2017, at 1425 EDT, while performing Engineered Safeguards Actuation System (ESAS) quarterly High Pressure Injection/Low Pressure Injection Logic and Component testing, an unintended test signal was generated when a test switch was moved to the OFF position but went slightly past this position and engaged contacts for the Test no. 1 position. When examined, the test switch was found to be degraded which allowed the switch to move past the center position and engage the test no. 1 contacts. This resulted In a partial actuation of 'B'- train ESAS components. It also resulted in an injection to the reactor coolant system (RCS). The test signal was immediately removed by operators and the inadvertently started equipment secured. The plant was operating at 100% power when the event occurred. There were no valid signals or plant conditions present to warrant the safety system actuation. The 'B' Emergency Diesel Generator rolled on air start but did not get up to full speed. Decay Heat Removal Pump 'B' started and the Decay Heat Removal Injection valve 4B opened, Make-Up Pump 'C' started, Make-Up Pump suction valve 14B opened, Make-Up pump discharge valves 16C and 16D opened, Spent Fuel Pump 1B tripped off, Air Handling Fan 18 tripped off and Air Handling Fan 1C trip tripped off. These components properly functioned from the inadvertent test signal and were secured prior to any adverse impact to plant operation. There was a small injection of borated water into the RCS. The plant remained stable at 100% power operation. Pursuant to 10 CFR 50.73(a)(1) the following information is provided as a sixty (60) day telephone notification to the NRC. This notification, reported under 50.73(a)(2)(iv)(A), is being provided in lieu of the submittal of a written LER to report a condition that resulted in an invalid partial actuation of the 'B' train of the Engineered Safeguards Actuation System (ESAS) as it was not part of a pre-planned sequence. The Licensee notified the NRC Resident Inspector. | Reactor Coolant System Emergency Diesel Generator Decay Heat Removal | |
| ENS 51695 | 2 December 2015 02:19:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Emergency Feedwater Actuation | On December 1, 2015, at 2119 EST, with Unit 1 in power operation mode, during a planned maintenance activity, an invalid Heat Sink Protection System (HSPS) actuation occurred. At the time of the event, electrical maintenance technicians were verifying a HSPS relay contact state using an electrical test meter. The contact was being verified open by recording both voltage and resistance readings across the contact. The technicians first measured voltage. No voltage was found, indicating the relay contact was open, as expected. The technicians then measured for resistance across the open contact. Test meters have lower circuit impedance when measuring resistance as opposed to voltage, which can result in electrically bridging across open contacts. When the meter was installed across the open contact to obtain the resistance reading, the HSPS actuation circuit logic was completed and the inadvertent HSPS actuation occurred. The HSPS actuation resulted in the steam driven Emergency Feedwater (EFW) pump automatically starting and control valves receiving actuation set point signals. There was no emergency feed water injection into the steam generators. At the time of the inadvertent HSPS actuation, steam generator operating levels were above the HSPS actuation setpoint. The specific train and system that actuated was the Heat Sink Protection System, Emergency Feedwater System Actuation on Loss of All Reactor Coolant Pumps (RCP) Train A. The HSPS Loss of all RCP Train A actuation was complete. The EFW valves and EFW steam driven pump started and functioned successfully. This is reported under 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of HSPS Loss of all RCP Train A and in accordance with 10 CFR 50.73(a)(1), this notification of the invalid actuation is provided in lieu of a written LER. The Licensee notified the NRC Resident Inspector. | Steam Generator Feedwater Emergency Feedwater System | |
| ENS 45324 | 10 July 2009 06:38:00 | 10 CFR 50.73(a)(1), Submit an LER | Electrical Short Circuit Resulted in Partial High Pressure Injection | This event is being reported via a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER. In this case, the telephone report is not considered an LER. This report is being made under 10 CFR 50.73(a)(2)(iv)(A). During a maintenance activity to replace an Engineered Safeguards Actuation System (ESAS) relay, one of the two High Pressure Injection (HPI) valves (MU-V-16C) in the 'B' train partially opened. The HPI system consists of the 'A' and 'B' trains, with each train containing two HPI valves. The cause of the partial opening of the HPI valve was inadvertent contact with adjacent energized circuits during the replacement of the ESAS relay. This resulted in a momentary short circuit, which bypassed the normal actuation logic, causing the HPI valve to open approximately 0.17 inches before blowing the control power fuse that stopped the valve movement. The event resulted in the inadvertent transfer of approximately 1000 gallons of water from the Make-up Tank into the Reactor Coolant System (RCS), before the valve could be restored to the closed position. No other valves or components actuated as a result of the inadvertent short circuit. RCS volume and pressure were stabilized and returned to normal. The 'B' HPI train had been declared inoperable and the unit entered a 72 hour LCO at 1:03 AM on 7/10/2009 due to configuration requirements needed for the planned ESAS relay replacement. The inadvertent partial 'B' train HPI did not impact the 'A' HPI train, and the unit remained at full power during this event. Following troubleshooting and replacement of the control power fuse, MU-V-16C was tested and restored to OPERABLE at 4:59 AM on 7/11/2009. The licensee notified the NRC Resident Inspector. | Reactor Coolant System | |
| ENS 44715 | 24 October 2008 18:18:00 | 10 CFR 50.73(a)(1), Submit an LER | Inadvertent Actuation of Engineered Safeguards System from Relay Sensing Circuit | This event is being reported via a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER. In this case, the telephone report is not considered an LER. This report is being made under 10CFR 50.73 (a)(2)(iv)(A). During Engineered Safeguards Actuation System (ESAS) logic testing on October 24, 2008, an invalid actuation of the following heat removal systems occurred: 'B' train of the Decay Heat River Water System (DR), 'B' train of the Decay Heat Closed Cooling Water System (DCCW), and the 'B' train of the Nuclear Services River Water System (NR). There was no injection into the Reactor Coolant System. The invalid actuation occurred when the channel under test was taken to its tripped position. Since ESAS utilizes a 2 out of 3 logic for actuation, another actuation signal was present on one of the two channels not being tested, satisfying the actuation logic for the affected systems. The invalid actuation of these heat removal systems during testing on October 24, 2008 was due to oxidation on a silver-plated contact in one of the other two channels that was not being tested. This contact oxidation caused a higher input resistance to the timer relay, which resulted in an inadvertent actuation of the relay and its associated systems. The contact oxidation was caused as a result of using silver plated contacts in a low voltage application (approximately 12 VDC). During this invalid actuation, the heat removal systems were fully actuated. These heat removal systems functioned successfully and the operation of these systems did not have any adverse impact on plant operation. All of the silver-plated contacts in the affected circuits will be replaced with gold-plated contacts. The contacts are scheduled to be replaced by December 18, 2008. The NRC Resident Inspector has been notified. | Reactor Coolant System | |
| ENS 43498 | 27 June 2007 12:28:00 | 10 CFR 50.73(a)(1), Submit an LER | Failed Relay Starts One Train of the Decay Heat River Water System | This event is being reported via a telephone notification to the NRC Operations Center within 60 days after discovery of the event instead of submitting a written LER. In this case, the telephone report is not considered an LER. This report is being made under 10CFR 50.73 (a)(2)(iv)(A). During Engineered Safeguards Actuation System (ESAS) logic testing on June 27, 2007, an invalid actuation of the 'A' train of the Decay Heat River Water System (DR) occurred. The DR is comprised of the 'A' and 'B' trains, and serves as the reactor's ultimate heat sink. The ESAS has three independent input channels, which cause actuation in a two out of three logic. During ESAS logic testing, the channel under test is placed in the tripped state. Actuation relays in the other two channels should remain energized by the outputs from the other two channels not under test. The invalid actuation of the 'A' DR train during testing on June 27, 2007, was due to a failed ESAS relay in one of the other two channels not being tested. During this invalid actuation, the 'A' DR train was fully actuated. The operation of this normally standby system did not have any adverse impact on plant operation, nor any negative impact on the DR. The failed relay that caused the invalid actuation during ESAS logic testing did not impact the OPERABILITY of the ESAS, since the relay was failed in the actuated state. The failed relay was replaced on June 29, 2007. The licensee notified the NRC Resident Inspector. |