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| Entered date | Event description | |
|---|---|---|
| ENS 48978 | 28 April 2013 14:47:00 | This is a 60-day optional telephonic notification of an invalid actuation of the Unit 1 Turbine Driven Auxiliary Feed Water Pump (TDAFWP). This report is being made under 10CFR50.73(a)(2)(iv)(A). On 28 February 2013, at 1534 CST, during restoration of the Unit 1 TDAFWP from steam admission valve maintenance, steam was inadvertently admitted to the TDAFWP turbine, resulting in the TDAFWP delivering auxiliary feed water flow to the steam generators. On 28 February 2013, the Unit 1 TDAFWP was removed from service for replacement of the hand switch and air-supply solenoid to the TDAFWP steam admission valve. The tagout utilized for this maintenance closed the TDAFWP trip-throttle valve to ensure that steam remained isolated from the TDAFWP. During the replacement of the hand switch and air-supply solenoid, the normally closed steam admission valve failed to the open position. This went unnoticed by Operations personnel. When the TDAFWP trip throttle valve was reopened during post-maintenance restoration, the failed-open steam admission valve provided a steam path to the TDAFWP. The TDAFWP started and supplied approximately 60-70 gpm feed water flow to each steam generator for approximately one minute prior to being secured by the operators. No main turbine load reduction was required to maintain reactor power within limits. This was an invalid actuation of the TDAFWP due to no automatic actuation signals being present and no operator actions being taken with the intent of starting the TDAFWP. During a normal TDAFWP start, the steam admission valve is opened in concert with steam supply valves aligned in series with the steam admission valve. During this event, the steam supply valves remained closed (steam flow bypassed these valves through normally open warm-up valves). Therefore, this event was a partial actuation of the TDAFWP. The TDAFW Pump is a third, independent train of AFW. No other portions of the auxiliary Feed Water System actuated or received actuation signals during this event. The primary cause of this event was determined to be not complying with the tagging checklist when sequencing the tagout restoration steps. Corrective actions are scheduled to complete on 30 May 2013. The licensee will notify the NRC Resident Inspector. |
| ENS 46829 | 8 May 2011 13:48:00 | The facility Technical Support Center (TSC) has been rendered non-functional due to a malfunctioning TSC ventilation system. Investigation into the cause of elevated TSC room temperature led to the discovery of a tripped condensing unit compressor. Repairs to the TSC ventilation system were immediately initiated with high priority. Compensatory measures per site procedure FNP-0-EIP-6.O (TSC Setup and Activation) for maintaining emergency assessment, off-site response, and off-site communication capabilities were immediately put in place. These measures include the conditional relocation of the TSC staff in the event of a declared emergency if the Emergency Director deems the TSC to be uninhabitable. The licensee will notify the NRC Resident Inspector. |
| ENS 46765 | 18 April 2011 13:24:00 | The facility Technical Support Center (TSC) has been rendered non-functional due to a pre-planned and scheduled maintenance period for the Technical Support Center ventilation system. The maintenance activities include replacement of the evaporator coil, fan, and expansion valve. The TSC ventilation maintenance will be worked with high priority and is expected to be complete prior to 1200 EDT on 4/19/11 . Pre-arranged compensatory measures for maintaining emergency assessment, off-site response, and off-site communication capabilities were put in place prior to the beginning of the TSC ventilation maintenance and will remain in place for the duration of the maintenance period. These measures include the relocation of the TSC staff in the event of a declared emergency IF the Emergency Director deems the TSC uninhabitable. The NRC Resident Inspector has been notified. |
| ENS 45812 | 4 April 2010 20:56:00 | On 4/4/10 at 1245 (CDT), three RHR system snubbers were declared inoperable due to visual inspection identifying empty reservoirs for the snubbers. The inoperability of the snubbers rendered both trains of RHR cooling inoperable. On 4/4/10 at 1545, ultrasonic testing identified voided piping on the common RWST (Refueling Water Storage Tank) suction line to the RHR pumps. This condition also resulted in inoperability of both trains of RHR for the ECCS (Emergency Core Cooling System) mode of operation. At the time of these discoveries, Unit 2 was in mode 4, proceeding to mode 5 for a refueling outage. The inoperability of both trains of RHR represents a condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat and mitigate the consequences of an accident. Replacement of the snubbers is in progress. Following completion of snubber replacement, Unit 2 will proceed to mode 5 at which point ECCS capability is not required. Resolution of the voided piping will be accomplished following mode 5 entry. The snubbers are in containment and were last checked during the previous refueling outage. The voiding in the RHR suction line only affects suction from the RWST and not when suction is aligned to the Reactor Coolant System. The licensee will notify the NRC Resident Inspector.
An eight hour report (EN #45812) per 10CFR50.72(b)(3)(v)(B) and 10CFR50.72(b)(3)(v)(D) was conservatively reported because both trains of Residual Heat Removal (RHR) system were thought to be inoperable based on the initial visual inspection of three hydraulic snubbers. In addition, initial ultrasonic testing at the RHR suction line to the refueling water storage tank (RWST) identified what was thought to be voided piping. Subsequent visual inspections and testing demonstrated that all three snubbers had adequate oil to ensure that the snubbers would perform their intended function. In addition, the ultrasonic testing was reviewed and determined that the technique for the coupling gel application between the ultrasonic detector and piping was not adequate for an accurate test. The ultrasonic inspection was performed again using the correct detector to piping coupling technique and it was determined that the RHR piping had adequate water level. Therefore, based on more accurate subsequent results of snubber and ultrasonic testing, the RHR system was never inoperable. The three snubbers thought to be inoperable were removed and replaced with snubbers previously verified to be operable. After removal, the snubbers were visually inspected and tested. Two of the three hydraulic snubbers share a common oil reservoir. This common reservoir was found to be completely full of clear oil which made it difficult to determine reservoir oil level while installed in the plant. The third snubber oil reservoir was one-third full. The removed snubbers have been tested to confirm they would have operated as designed. The ultrasonic testing of RHR piping was started as a result of SNC's response to NRC Generic Letter 2008-01. This testing requires a coupling gel to be used between the ultrasonic detector and the RHR piping to ensure accurate water level results. Based on the initial ultrasonic test results it was thought that the RHR piping had voids. However, when the coupling process was reexamined, it was determined that additional coupling gel was needed for accurate results. When the ultrasonic test was performed again with the proper coupling process, it was determined that the RHR piping had adequate water and that voiding did not exist. The second ultrasonic inspection technique was reviewed and confirmed the coupling process utilized was correct. In summary, a loss of safety function on both trains of RHR did not exist and the 50.72(b)(3)(v)(B) and 50.72(b)(3)(D) report (EN # 45812) is retracted. The licensee notified the NRC Resident Inspector. Notified R2DO (Moorman). |
| ENS 45673 | 3 February 2010 03:14:00 | On 2/2/10, at 1615 (CST), the Unit 1 TDAFW (Turbine Driven Auxiliary Feed Water) Pump was declared inoperable due to a high temperature identified on an electrical cable in the TDAFW UPS (Uninterrupted Power Supply). The 1B Diesel Generator had previously been removed from service for scheduled maintenance. As required by the Diesel Generator LCO Required Action Statement, the Unit 1 'B' MDAFW (Motor Driven Auxiliary Feed Water) Pump was declared inoperable at 2015 (CST), on 2/2/10, due to the combination of its inoperable emergency power supply and inoperable redundant equipment. This resulted in two of three trains of Auxiliary Feed Water being inoperable. Because two out of the three trains of AFW (Auxiliary Feed Water) are required to meet flow requirements for limiting design basis accidents, this represents a condition that could have prevented the fulfillment of a safety function. Repairs to the electrical cable were immediately initiated. At 2216 (CST), on 2/2/10, the Unit 1 TDAFW Pump was returned to operable status, allowing the 1B MDAFW Pump to be declared operable, and restoring the safety function. The licensee determined that the high temperature in the electrical cable was caused by a high resistance between the lug and cable connection. The licensee will notify the NRC Resident Inspector. |
| ENS 44855 | 16 February 2009 22:09:00 | No release of radiation has occurred as a result of this event. At 1655 CST, the Unit One 'H' 4160V bus phase two differential relay actuated when the relay panel was inadvertently bumped. This resulted in the de-energization and lockout of the 1H 4160V bus and the auto start of the 1C Emergency Diesel Generator (EDG). Recovery actions have been successful in restoring power to the affected switchgear. All equipment functioned as expected. Normal equipment lineup has been restored. Unit One remained at full power during this event. The 1C EDG never picked up any loads because of the lockout on the 1H bus. Some loads were lost including an air compressor and some oil pumps but this equipment was either re-started or backups were started within about two hours. The licensee notified the NRC Resident Inspector. |