Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 42929 | 24 October 2006 09:08:00 | At 0142 on October 24, 2006, while aligning the High Pressure Core Spray system for surveillance testing of the Reactor Core Isolation Cooling System Storage Tank Level instrumentation, 1E22-F015, the Suppression Pool suction valve for the High Pressure Core Spray pump, failed to stroke fully open. High Pressure Core Spray was declared inoperable as a result. This event is considered a loss of a single train system needed to mitigate the consequences of an accident. The High Pressure Core Spray system was restored to an operable condition at 0506 on October 24, 2006 after the suction valve was successfully stroked open and the HPCS suction source was aligned to the Suppression Pool in accordance with Technical Specification Limiting Condition for Operation 3.5.1. The cause of the event is currently under investigation. All other Emergency Core Cooling systems were fully operable during the time period HPCS was inoperable. The Senior Resident Inspector has been notified by the licensee.
Upon further review of this event, the High Pressure Core Spray (HPCS) system remained operable. Based upon valve motor operator thrust verification testing data and troubleshooting, the cause of the suppression pool suction valve for the HPCS pump stopping in mid-position was determined to be tripping of the open-direction torque switch prior to the open limit switch setpoint. Normally, the condition of the open-direction torque switch has no safety-related consequence since the torque switch is bypassed during design basis events and the valve's motor gearing capability is sufficient to open the valve when the torque switch is bypassed. During this event, as directed by the surveillance test procedure, operators placed the HPCS Motor Operated Valve (MOV) test switch to the test position which resulted in the open-direction torque switch not being bypassed (i.e., was in the circuit) during repositioning of the HPCS suppression pool suction valve. Due to placing the HPCS MOV test switch to test, operators entered the action of Operational Requirements Manual section 2.5.2 (Motor Operated Valves Thermal Overload Protection). The action requires operators to return the MOV test switch to normal (removing the torque switch from the circuit) if an emergency condition occurs requiring valve repositioning. As operators were opening the HPCS suppression pool suction valve for testing, suction for the HPCS pump was aligned from the RCIC storage tank. When the HPCS suction valve from suppression pool stopped in mid-position, the HPCS suction valve from the RCIC storage tank was still fully open (per design, stays full open until the HPCS suppression pool suction valve is full open). Therefore, if an accident occurred requiring HPCS to initiate and inject water into the reactor pressure vessel during this event suction would have initiated from the RCIC storage tank. The HPCS system can take suction from either the RCIC storage tank or the suppression pool, and a HPCS initiation signal does not automatically swap HPCS pump suction from the RCIC storage tank to the suppression pool or vice versa. The operators immediately recognized the HPCS suppression pool suction valve did not fully open. If an accident condition occurred, operators would reposition the HPCS MOV test switch to Normal (to bypass the open torque switch). In the event a condition requiring a HPCS suction transfer to the suppression pool occurred, the suppression pool suction valve would fully open and the RCIC storage tank suction valve would fully close, completing the required suction shift. On this basis, the HPCS system was capable of performing its function to mitigate the consequences of an accident and this issue is not reportable under 10 CFR 50.72(b)(3)(v)(D). The NRC Resident was notified of this retraction. R3DO(Cameron) notified. |
| ENS 42430 | 20 March 2006 08:28:00 | At 0453 CST on March 20, 2006, a main turbine trip occurred resulting in a reactor scram. All control rods fully inserted on the scram signal. All systems performed as expected. Reactor water level is being controlled in the normal operating band and reactor pressure is being controlled at 600 psig. The cause of the turbine trip is under investigation. There is no indication that the turbine trip was caused by an actual parameter reaching a trip setpoint. A turbine Low Vacuum trip alarm is indicated in the Main Control Room and is the current focus of troubleshooting activities. Actual main condenser vacuum is at its normal value. The site is on off-site power, and the EDG's are available if required. All safety related systems are available if required. The licensee notified the NRC Resident Inspector. |
| ENS 42477 | 5 April 2006 16:07:00 | The following 60-day report is being made under 50.73 (a)(2)(iv)(A) for an invalid actuation of Division 1 containment isolation valves that occurred at 2259 hours on February 7, 2006. As allowed by 10CFR50.73(a)(1) this notification is being made via telephone. NUREG-1022, Revision 2 identifies the information that needs to be reported as follows: (a) The specific train(s) and system(s) that were actuated. An unexpected actuation of Division 1 containment isolation relays occurred during performance of WO 416930-02, EM - Agastat Relay Luayvg514b Replacement in panel 1H13P861. Momentary, inadvertent contact occurred between the top row R1-M1 pins of the Agastat relay being inserted and the second row T1-B1 contacts of the installed relay base while the Electrical Technician was attempting to align the relay for seating, prior to applying full seating force to the relay. The relay actuations resulted in closure of Division 1 isolation valves in the Fuel Pool Cooling and Cleanup, Suppression Pool Cooling and Cleanup, Component Cooling Water, Service Air, Containment and Drywell Equipment and Floor Drains, and Makeup Condensate systems. (b) Whether each train actuation was complete or partial. The actuations were complete for the portions that were enabled while relay testing was in progress. (c) Whether or not the system started and functioned successfully. There no system starts associated with this event The NRC Resident Inspector was notified of this notification. |
| ENS 40868 | 13 July 2004 18:57:00 | On July 13, 2004 at 1610 CDT, the Clinton Power Station 345 KV unit output breakers GCB 4506 and 4510 opened resulting in a turbine control valve fast closure. This caused a reactor protection system actuation and reactor scram. Clinton was in Mode 1, operating at 95% rated thermal power when the event occurred. A tornado warning was in effect at the time of the event and weather conditions were degrading in the area surrounding the plant. The exact cause of the trip of the unit breakers is not yet known. All systems responded as expected following the scram with the exception of Reactor Recirculation pump A which tripped off instead of downshifting to slow speed on a reactor water level 3 signal. The unit is currently in Mode 3 with reactor pressure vessel level and pressure in their normal bands. Recirculation Pump "A" remains secured until the licensee completes their investigation. All control rods fully inserted following the scram. The Main Condenser is in service removing decay heat. All ECCS equipment including the EDGs are available, if needed. The licensee informed the NRC Resident Inspector. |
| ENS 40231 | 8 October 2003 12:20:00 | Security weapon and holster left unattended. Immediate compensatory actions taken upon discovery. Contact the HOO for details. The licensee will be notifying the NRC Resident Inspector and has notified the R1TAS (Greg Smith).
The licensee is retracting this report based upon further review. Contact the HOO for details. The licensee will inform the NRC Resident Inspector. Notified R1DO (Ron Bellamy). |