Semantic search
Jump to navigation
Jump to search
| Entered date | Event description | |
|---|---|---|
| ENS 50110 | 12 May 2014 17:37:00 | At 0845 (CDT) during planned maintenance, the annunciators which would indicate flooding in the Emergency Core Cooling System (ECCS) Pump Rooms to the max safe water level in the rooms were disabled. These max safe water level alarms are used to assess the emergency action level (EAL) entry condition (HA4) for flooding (ALERT classification). Compensatory measures are in place to perform periodic walk downs of RHR A, RHR B, RHR C, HPCS, LPCS, RCIC rooms and the fuel building basement once per shift to verify no leakage. Additionally, the annunciator for max normal water level is operational and pump run times are still available in the Main Control Room to indicate increased leakage into the ECCS rooms. This max normal water level alarm is used to assess the EAL entry condition (HU4) for flooding (Unusual Event classification) and EOP-8 entry. Since the operator compensatory actions that were established are not proceduralized, then this is reportable as a loss of emergency assessment capability under 10 CFR 50.72(b)(3)(xiii). The expected return to service time of all alarms is 2300 CDT. The licensee will notify the NRC Resident Inspector. |
| ENS 49958 | 25 March 2014 22:44:00 | The plant was stable at 85 percent power when off-gas flow started lowering. The operating crew entered the loss of vacuum off-normal procedure and commenced an emergency power reduction to attempt to slow/halt the loss of vacuum while attempting various prescribed actions in the off-normal procedure. When vacuum reached 24 in. Hg, a rapid plant shutdown was performed as prescribed in the off-normal procedure. Power was at 46 percent when a rapid plant shutdown was commenced with the mode switch placed in shutdown at 1942 CDT. All control rods fully inserted on the scram, no emergency core cooling system injected or was required, no safety/relief valve(s) lifted and all systems responded as expected on the scram. The plant will remain in mode 3 with normal makeup from the feedwater system and pressure control on the turbine bypass valves with the main condenser available as a heat sink. All vital and non-vital electrical busses are powered from reserve off-site sources and no emergency diesel generators started on the scram. The cause of the loss of vacuum is under investigation. The licensee notified the NRC Resident Inspector. |
| ENS 49617 | 9 December 2013 01:15:00 | While operating at rated electrical power, the station experienced a transformer fault which resulted in a loss of Division 1 480 VAC power. This resulted in the operators inserting a Manual Scram due to loss of Instrument Air to Containment and the scram air header. On the scram, all control rods fully inserted and no safety relief valves lifted. Reactor vessel level is being maintained by normal feedwater and decay heat is being removed via steam to the main condenser through the steam bypass valves. The plant is currently in Mode 3 and proceeding to Mode 4 to comply with Technical Specification requirements. The plant is in a normal shutdown electrical lineup with the exception of the loss of Division 1 480 VAC power. Reporting in accordance with 10CFR50.72(b)(3)(v)(C) due to loss of normal ventilation to secondary containment which resulted in a positive secondary containment pressure for approximately 15 minutes. Secondary Containment required pressure was restored at 2043 CST. Reporting in accordance with 10CFR50.72(b)(3)(v)(D) due to loss of Division 1 480 VAC power resulting in loss of a single train of Low Pressure Core Spray. The licensee has notified the NRC Resident Inspector. |
| ENS 48812 | 7 March 2013 11:52:00 | While operating at rated electrical power, a main generator trip and subsequent turbine trip resulted in a reactor scram. The cause of the generator trip is under investigation. All systems operated as expected with no complications. The plant is stable in Mode 3. The licensee notified the NRC Resident Inspector and the State of Illinois. |
| ENS 48377 | 4 October 2012 16:52:00 | At 1301 (CDT) on October 4, 2012, during the restoration of a single Farmer City owned siren, DeWitt County Emergency Dispatch Center inadvertently activated all of Clinton Power Station's emergency sirens instead of the Farmer City owned siren. A siren in the Farmer City area had fallen off a pole, and following repairs, instead of testing the individual siren, the Dispatch Center inadvertently actuated all 40 Clinton Power Station sirens. The sirens were actuated for approximately 1 minute and 14 seconds. The Clinton Power Station siren system covers parts of four surrounding counties (DeWitt, Piatt, McLean, and Macon). A spurious actuation of one or more emergency response sirens is reportable under 10CFR50.72(b)(2)(xi) addressing a notification of a government agency related to the health and safety of the public. The NRC Resident Inspector has been notified. All of the affected county Emergency Management Agencies have been notified. The DeWitt County Sheriff has notified various media outlets. |
| ENS 46603 | 8 February 2011 15:06:00 | During the performance of a Fire Protection self assessment, it was discovered that a calculation for the safe shutdown analysis has an assumed action for an operator to locally depress the internal breaker trip plunger to trip the High Pressure Core Spray (HPCS) pump in response to a fire in the main control room. However, due to personnel safety concerns related to potential arc flashing events associated with this action, the remote shutdown procedure was revised to locally close the HPCS injection valve (1E22FOO4) in lieu of depressing the internal breaker trip plunger. During engineering's review of this procedure and supporting calculation, it was determined that the HPCS system could be initiated due to concurrent fire induced hot short cable damage to the two automatic initiation logic instrument cables routed in the same raceway in the area. In this event, even if the HPCS breaker could be tripped or the HPCS injection valve could be closed locally, HPCS would continue to fill the reactor pressure vessel (RPV) and flood the main steam lines. Once pressure reaches the setpoint for the Main Steam Safety Relief Valves (MSSRVs), they would lift and discharge mixed-phase water through the discharge line to the suppression pool. This conservatively postulated scenario would place the MSSRVs and their associated tailpipes in an unanalyzed condition for the stresses expected during the two-phase flow event. While it is not expected that a failure of the MSSRV discharge line will occur, a confirmatory analysis will be performed. Compensatory measures for Multiple Spurious Operations have been determined to be adequate until the analysis is complete. The licensee added additional fire zone surveillance to operator plant walk downs and will investigate to determine further corrective actions. The license has notified the NRC Senior Resident Inspector. |