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| Entered date | Event description | |
|---|---|---|
| ENS 52484 | 11 January 2017 16:56:00 | On September 16, 2016, Comanche Peak reported an unanalyzed condition and potential loss of safety function per 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v) related to Teflon (PTFE) installed in the pressure gauge diaphragm seal assemblies for all four of the Centrifugal Charging Pumps and both of the Positive Displacement Charging Pumps on Units 1 and 2 (EN#52244). On November 14, 2016, this event was subsequently retracted. On December 12, 2016, during the ongoing extent of condition review, Teflon was also found to be installed in the suction and discharge pressure gauge diaphragm seal assemblies for the Unit 1 and 2 Containment Spray Pumps. On January 11, 2017 at approximately 1500 CDT, the reportability evaluation determined that reasonable assurance did not exist that the Containment Spray system would have been able to fulfill its design function of removing heat from the containment environment without impacting the applicable dose limits. Teflon (PTFE) is a restricted material normally prohibited from use in contact with reactor coolant or in radiation environments. Teflon (PTFE) is not radiation tolerant and degrades in a radiation environment. The Teflon (PTFE) used in these diaphragm seal assemblies could fail during a postulated Loss of Coolant Accident (LOCA) which could cause the Containment Spray Pumps on Units 1 and 2 to be inoperable, and exceed system leakage limits. This could challenge dose limits and in plant post-accident accessibility. This represents an unanalyzed condition. The pressure gauges and diaphragm seals for all of the Unit 1 and 2 Containment Spray Pumps have been isolated and the Unit 1 and 2 Containment Spray Pumps are operable. The Teflon (PTFE) has likely existed in these diaphragm seals since initial plant licensing. Luminant Power is continuing to investigate the extent of this condition and potential repair techniques. The NRC Resident Inspector has been notified. |
| ENS 50965 | 7 April 2015 18:50:00 | Luminant Generation Company LLC (Luminant Power) has completed a review of seismic monitor performance at the Comanche Peak Nuclear Power Plant (CPNPP) over the last three years. The CPNPP emergency preparedness plan requires seismic monitoring instruments to diagnose an earthquake for emergency action levels (EAL) HA1.1 (seismic event greater than OBE (operating basis earthquake) and HU1.1 (identified seismic event that is less than the OBE). The seismic monitor performance review identified one unplanned instance of monitor unavailability and three instances when planned monitor outage durations exceeded 24 hours. Any loss of seismic monitoring capability results in a major loss of assessment capability for the Alert (HA1.1) and a degraded assessment capability for the Unusual Event (HU1.1) emergency classification. The seismic monitor is currently functional, however it was determined to be non-functional on the following dates: Unplanned out-of-service: 12/4/2013 through 12/1 0/2013 Planned out-of-service lasting greater than 24 hours: 5/16/2012 through 5/24/2012 3/20/2013 through 3/27/2013 9/29/2014 through 10/1/2014 The loss of assessment capability is reportable to the NRC within 8 hours of discovery in accordance with 10 CFR50.72(b)(3)(xiii). This report is required per 10 CFR50.72(a)(1)(ii) as an event that occurred within 3 years of the date of discovery. The seismic monitor issues and the missed reporting of the loss of assessment capability have been documented in the CPNPP corrective action program. This review was prompted by the licensee's evaluation of industry's operating experience. A similar report was received from Limerick Generating Station - EN # 50951. The licensee informed the NRC Resident Inspector. |
| ENS 44152 | 21 April 2008 00:37:00 | While ramping the Unit 1 Turbine following a forced unit outage, vibrations on the number 4 bearing increased to 13.9 mils. The ramp was stopped and a rapid load reduction was initiated. Due to sustained vibrations (>14.1 mils) after ramping the turbine down, the Unit 1 reactor was manually tripped. Unit 1 has been stabilized at Hot Shutdown. All three auxiliary feedwater pumps automatically initiated as designed on low-low steam generator level following the trip. Currently RCS temperature is being maintained stable at 547 degrees. All systems functioned as required following the reactor trip. There were no radiation releases due to this event, nor were there any personnel injuries or contamination events. This event is being reported in accordance with 10 CFR 50.72 (b)(2)(iv) and 10 CFR 50.72 (b)(3)(iv). Upon exiting the refueling outage in 11/07 the main turbine had a vibration issue of about 11 or 12 mils. Decay heat is being removed via the steam dumps to the condenser. Unit 2 was not affected during this event. Offsite power was lined up normally. The licensee notified the NRC Resident Inspector. |