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| Entered date | Event description | |
|---|---|---|
| ENS 54281 | 16 September 2019 14:35:00 | On 9/16/19 at 0817 CDT, the Division 1 and Division 2 reactor water cleanup (RT) system differential flow instrumentation was declared inoperable due to failing downscale caused by flashing in the sensing lines that occurred during reactor cooldown for refueling outage C1R19. The Division 1 and Division 2 RT differential flow instrumentation were declared inoperable in accordance with Technical Specification 3.3.6.1 Conditions D and E which require restoring at least one division of instruments to operable status within one hour. This condition renders the leakage detection system incapable of performing its safety function, thus it is reportable under 10 CFR 50.72(b)(3)(v)(D). In response to the above, system alignment was changed to increase subcooling to restore indication. Division 1 and 2 Division RT differential flow instrumentation were declared operable at 0852 on 9/16/19. The NRC Resident Inspector has been notified. |
| ENS 53463 | 20 June 2018 17:51:00 | On June 20, 2018, at 1145 hours (CDT), during panel walkdown, it was identified that High-Pressure Core Spray (HPCS) injection valve 1E22F004 was in the open position. Valve 1E22F004 is normally closed for containment integrity purposes. Operations personnel verified that the valve was open locally and that the plant computer indicated the valve is in the 'not closed' position. No alarms or status lamps indicated why the valve would be open and there was no valid demand signal. Reactor power, pressure, level, and feedwater parameters remain steady and unchanged, with no indication of HPCS injection having occurred or in progress. A low-water level signal, or a high drywell pressure signal, or manual operation initiates HPCS. When a high-water level in the reactor vessel is detected, HPCS injection is automatically stopped by a signal to close injection valve 1E22F004. With valve 1E22F004 in the open position without a demand signal, closure on a high reactor water level condition was not assured. Therefore, HPCS was declared inoperable. The following Technical Specifications were entered: 3.5.1, Emergency Core Cooling Systems (ECCS) - Operating and 3.6.1.3, Primary Containment Isolation Valves (PCIVs). Subsequently, HPCS injection valve 1E22F004 was observed to be cycling without operator action. The valve was deactivated in the closed position to assure the containment isolation function. The cause of valve 1E22F004 cycling without operator action is under investigation. HPCS is a single train safety system that consists of a single motor-driven pump, a spray sparger in the reactor vessel, and associated piping, valves, controls and instrumentation. HPCS is part of the ECCS network, which also includes Low-Pressure Core Spray, Low-Pressure Coolant Injection, and the Automatic Depressurization system. This event is being reported as an 8-hour non-emergency notification per 10 CFR 50.72(b)(3)(v) as, 'Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (A) Shut down the reactor and maintain it in a safe shutdown condition; (B) Remove residual heat; (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident.' The licensee notified the NRC Resident Inspector. |
| ENS 52782 | 2 June 2017 11:13:00 | On 6/2/2017 at 0241 CDT, Clinton Power Station entered Mode 2 with secondary containment boundary doors propped open. Specifically, both doors for Reactor Water Cleanup (RT) 'B' pump room were propped open with welding cables routed through pump room doors to perform welding in the RT pump room. At 0300 CDT, a Senior Reactor Operator identified that the doors were propped open and Secondary Containment was declared inoperable. LCO 3.6.4.1 Required Action A.1 was entered to restore Secondary Containment to Operable in four hours. At 0324 CDT, the cabling for the welding machine was removed and the doors were closed. Investigation determined that authorization had been granted while in mode 4, when secondary containment was not required to be operable. The doors were propped open at the beginning of the shift, prior to the mode change to mode 2 (0241 CDT). This loss of secondary containment is reportable under 10 CFR 50.72(b)(3)(v)(C) as an event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material. The NRC Resident Inspector has been notified. |
| ENS 52750 | 12 May 2017 08:20:00 | At 0045 (CDT) on May 12, 2017, it was discovered that a Primary Containment local leak rate test performed on Main Steam Isolation Valves (MSIV) exceeded its acceptance criteria. During Modes 1, 2, and 3, Technical Specification Surveillance Requirement 3.6.1.3.9 requires MSIV leakage for a single MSIV line to be less than or equal to 100 standard cubic feet per hour (scfh) (47,195 sccm) and requires the combined leakage rate for all MSIV leakage paths to be less than or equal to 200 scfh (94,390 sccm) when tested at 9 psig. As-found for the 'D' MSIV line leakage is 53,921.61 standard cubic centimeter per minute (sccm) for the 'D' Inboard MSIV 1B21F022D and 59,698.8 sccm for the 'D' Outboard MSIV 1B21F028D. As-found combined MSIV min-path leakage is 102,463 sccm. This event is being reported as a condition of the nuclear power plant, including its principal safety barriers, being seriously degraded per 10 CFR 50.72(b)(3)(ii)(A) since the Primary Containment Isolation Valves leakage limits for MSIVs were exceeded. The NRC Resident Inspector has been notified. |
| ENS 52043 | 24 June 2016 19:45:00 | On 06/24/2016 at 1511(CDT), an unexpected trip of a Fuel Building ventilation supply fan occurred followed by an exhaust fan trip and secondary containment differential pressure became positive. At 1512 (CDT), the standby fuel building ventilation fans auto started and secondary containment differential pressure was restored to Technical Specification required conditions. Secondary containment was declared INOPERABLE when Technical Specification-required differential pressure was not being maintained and LCO 3.6.4.1 Action A.1 was entered and exited for the given time period. Emergency Operating Procedure (EOP) - 8 was entered due to Secondary containment differential pressure reading positive (greater than 0 inches of water). This loss of secondary containment is reportable under 10CFR 50.72(b)(3)(v)(C) as an event or condition that could have prevented fulfillment of a safety function needed to control the release of radioactive material. The cause of the fuel building supply fan trip is under investigation. The NRC Resident Inspector has been informed. |
| ENS 49373 | 20 September 2013 18:00:00 | During the performance of a focused area self assessment (FASA) for the Clinton Power Station Fire Protection Program, the FASA team identified a noncompliance with the Safe Shutdown Analysis for a fire outside the Diesel Generator (DG) rooms (i.e., Fire Zone CB-1e, CB-1f, CB-2 and CB-4). The CO2 panels for each DG train are all located in the same area outside the DG engine bay rooms (i.e., 737' Control Building) and a fire in this area could cause fire damage to all three CO2 panels and/or wiring such that a trip (short) could be initiated to all three DG Ventilation (VD) fans. Loss of the VD fans (1VD01CA, B and C) results in loss of cooling in the DG rooms and ultimately loss of the diesels. This constitutes an Unanalyzed Condition that Significantly Affects Plant Safety. Compensatory measures are in-place that will allow these VD trips to be overridden and the VD fans to be restarted from the Main Control Room. The NRC Resident Inspector has been notified. |