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The query [[Category:ENS Notification]] [[Site::South Texas]] [[Scram::+]] was answered by the SMWSQLStore3 in 0.3454 seconds.


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 Entered dateSiteRegionScramReactor typeEvent description
ENS 518971 May 2016 22:14:00South TexasNRC Region 4Automatic ScramWestinghouse PWR 4-LoopAt 2021 (CDT) on 05/01/2016 Unit 1 automatically tripped due to a generator lockout. Relay 86/G1 actuated. The generator lockout resulted in a Unit 1 turbine trip and a reactor trip. Auxiliary Feedwater and Feedwater Isolation actuated as designed. All Control Rods fully inserted. No primary or secondary relief valves opened. There were no electrical problems. Normal operating temperature and pressure is (being maintained). There were no significant TS LCO's entered. This event was not significant to the health and safety of the public based on all safety systems performed as designed. Unit 2 was not affected. Unit 1 is stable in Mode 3, with decay heat being removed via dump valves to the condenser. The cause of the generator lockout is under investigation. The licensee notified the NRC Resident Inspector.
ENS 5168727 January 2016 01:44:00South TexasNRC Region 4Manual ScramWestinghouse PWR 4-Loop

At 2325 (CST) on 01/26/2016, Unit 1 was manually tripped due to loss of Feedwater on 'C' S/G (Steam Generator). The loss of Feedwater was a result of a failure on 'C' S/G Main Feedwater Regulating Valve that caused the valve to travel closed with no Operator action. Auxiliary Feedwater and Feedwater Isolation actuated as designed. All Control and Shutdown Rods fully inserted. Intermediate Range Nl 36 (Nuclear Instrument) failed above P10 and, as a result, Source Range Nuclear Instruments were manually energized. No primary or secondary relief valves opened. There were no electrical problems. Normal operating temperature and pressure (NOT/NOP) is 567 degrees F and 2235 psig. There were no significant TS LCOs entered.

This event was not significant to the health and safety of the public based on all safety systems performed as designed. Unit 2 was not affected. Decay heat removal is being controlled via Steam Dumps. Offsite power is in the normal electrical lineup. The NRC Resident Inspector has been notified.

ENS 5161521 December 2015 18:06:00South TexasNRC Region 4Manual ScramWestinghouse PWR 4-LoopAt 1519 (CST), the Main Turbine was tripped due to an Oscillating Governor Valve 2 (cause not known). At 1533, Unit 1 was manually tripped due to a feedwater isolation P-14 (caused by steam generator swell induced high steam generator level, resulting in) steam generator low level (after the isolation). Aux feedwater actuated as designed. All Control and Shutdown Rods fully inserted. Intermediate Range NI 36 failed above P-10 so SR-Nis (source range nuclear instruments) were manually energized. No primary relief valves lifted. All Steam Generator PORVs (power operated relief valves) opened. There were no electrical bus problems. Normal operating temperature and pressure (NOT/NOP) is 567F and 2235 psig. There were no significant TS LCOs (Technical Specification limiting conditions for operations) entered. This event was not significant to the health and safety of the public based on all safety systems performed as designed. Unit 2 was not affected and continues to operate at 100% power. The licensee has notified the NRC Resident Inspector.
ENS 486598 January 2013 18:15:00South TexasNRC Region 4Automatic ScramWestinghouse PWR 4-Loop

Fire in Unit 2 main transformer 2A. Reactor trip. Two train of offsite power lost to Unit 2. An Unusual Event was declared based on EAL HU-2 - Fire or explosion in protected area or switchyard which affects normal plant operations. At 1655 CST, South Texas Unit 2 declared an Unusual Event due to a main transformer fire. Unit 2 tripped from 100% power and is currently at 0% power in Mode 3. The transformer fire is out. In addition to the loss of the main transformer, several safety related electrical busses and non-safety electrical busses lost offsite power. The appropriate emergency diesel generators started and powered the safety related busses. Unit 2 is currently stable and on natural circulation due to the loss of power to the reactor coolant pumps. Auxiliary feedwater is functioning as required and decay heat is being removed through the steam generator atmospheric relief valves. Unit 1 was unaffected by the event. The licensee notified the NRC Resident Inspector. Notified DHS SWO, FEMA, DHS NICC and NuclearSSA via email.

  • * * UPDATE FROM RICK NANCE TO BILL HUFFMAN AT 2055 EST ON 1/8/2013 * * *

On January 8, 2013, at 1640 CST, a failure of the Unit 2 Main Transformer occurred which resulted in a Unit 2 automatic trip. The failure of the main transformer resulted in a fire and damage to the transformer. The onsite fire brigade responded to the fire. The fire was declared under control at 1649 CST and declared out at 1656 CST. No offsite assistance was required. An Unusual Event was declared at 1655 CST for initiating condition HU-2 (Fire or explosion in protected area or switchyard which affects normal plant operations) due to the main transformer fire. Due to the site electrical lineup at the time, the loss of the main transformer resulted in a loss of power to 4160 ESF buses 2A and 2C, and associated Standby Diesel Generators 21 and 23 started as required and loaded on to their respective buses. 4160 ESF bus 2B remained energized from offsite power during this event and Standby Diesel Generator 22 did not start since an undervoltage condition did not exist on its ESF bus. All three (3) motor-driven and the steam-driven Auxiliary Feedwater Pumps started as required. The Main Steam Isolation Valves were closed in accordance with procedure to limit plant cooldown. Decay heat is being removed via Auxiliary Feedwater with Steam Generator Power Operated Relief Valves. Following the reactor trip, Pressurizer Power Operated Relief Valve 656A momentarily lifted and re-closed. There were no personnel injuries and no radiological release as a result of this event. A press release has been issued. The plant is currently stable in Mode 3 and the cause of the event is under investigation. The Unusual Event was terminated at 1947 CST on 1/8/2013. The licensee notified the NRC Resident Inspector. Notified R4DO (Gaddy), NRR (Leeds), R4 (Reynolds), IRD (Gott), NRR EO (Hiland). Notified DHS SWO, FEMA, USDA, HHS, DOE, DHS NICC, EPA, and NuclearSSA via email.

ENS 486514 January 2013 14:19:00South TexasNRC Region 4Manual ScramWestinghouse PWR 4-LoopOn January 4, 2013, at 0941 hours (CST), Unit 2 was manually tripped after 2 shutdown rods unexpectedly dropped during monthly control rod surveillance testing. Shutdown Bank C rods were being inserted in accordance with the surveillance procedure, when 2 rods in Shutdown Bank E (D-8 and M-8) unexpectedly dropped. This met the criteria for a manual reactor trip, which was immediately performed. The appropriate procedures were entered to mitigate the transient and all systems responded as designed. Unit 2 is currently in Mode 3 and the cause of the 2 dropped rods is under investigation. All three (3) motor-driven and the steam-driven Auxiliary Feedwater Pumps started as required and have since been secured. Decay heat is being removed using normal startup feedwater with steam discharge to the main condenser via the bypass valves. Unit 2 is in a normal post trip electrical lineup. The licensee informed the NRC Resident Inspector.
ENS 4748529 November 2011 06:55:00South TexasNRC Region 4Automatic ScramWestinghouse PWR 4-Loop

At 0329 CST on 11/29/2011, Unit 2 experienced an automatic Reactor Trip while the plant was stable at 100% power in Mode 1. All systems actuated as designed. The reactor trip was caused by Generator Lockout. All ESF systems actuated as designed. The following systems actuated: Auxiliary Feedwater (AFW) and Feedwater Isolation. All control rods fully inserted. Steam Dump system valve FV 7485 failed open and was manually isolated. This caused a letdown isolation that was restored. No primary/secondary relief valves lifted. There were no electrical bus transfer problems. Normal operating temperature and pressure (of) 567 degrees F and 2235 psig (is being maintained). There were no significant TS LCOs entered. The electrical grid is stable and is supplying power to the plant via a normal shutdown electrical line-up. Decay heat is being removed via steam dumps to the condenser with AFW supplying the steam generators. There was no effect on Unit 1. The licensee has notified the NRC Resident Inspector.

  • * * UPDATE ON 11/29/11 AT 1312 EST FROM BRINKLY TO HUFFMAN * * *

The licensee has issued a press release concerning this event. The NRC Resident Inspector will be notified. R4DO (Farnholtz) informed.

ENS 463873 November 2010 12:09:00South TexasNRC Region 4Automatic ScramWestinghouse PWR 4-Loop

On November 3, 2010 at 1021 CDT, operators attempted to start the Unit 2 startup feedpump to support a two hour maintenance run. The feeder breaker for the startup feedpump exploded causing an undervoltage condition on Auxiliary Bus 1H and Standby Bus 1H which resulted in an automatic reactor trip due to reactor coolant pump undervoltage. All control rods inserted into the core. At 1038 CDT, the site declared an UNUSUAL EVENT (HU-2) due to an explosion in the protected area which affects normal plant operations. The standby diesel generator (EDG-23) started and loaded to the 'C' train loads which sequenced properly. The auxiliary feedwater system automatically started as expected providing feedwater to the steam generators. The normal feedwater pumps were secured. Decay heat is being removed from Unit 2 using the normal steam dump valves to the main condenser. There is no primary to secondary leakage. The plant is stable and in MODE 3 with no challenges to reactor safety. There was no impact on Unit 1. At 1240 CDT the licensee terminated the UNUSUAL EVENT. The licensee is investigating the cause of the breaker explosion and if the other standby diesel generator (EDG-21) should have started due to the undervoltage condition. The licensee notified the NRC Resident Inspector.

  • * * UPDATE FROM TAPLETT TO KLCO ON 11/3/10 AT 1530 EDT * * *

A News Release is being planned so this condition is also being reported pursuant to 10 CFR 50.72(b)(2)(xi). During the electrical fault condition, some Train A components stopped running although no Train A low voltage ESF actuation occurred, The reason for this occurrence is not fully understood, The breaker malfunction did not result in a fire. The licensee will notify the NRC Resident Inspector. Notified: R4DO (Spitzberg); NRR (Thorp); R4RA (Collins); NRR (Boger); IRD (Gott) DHS (Hill); FEMA (Hollis)

  • * * UPDATE FROM HARRISON TO SNYDER ON 11/4/10 AT 1920 EDT * * *

The licensee called to correct an editorial error in the original report above. The second sentence of the original report above should refer to Auxiliary Bus 2H and Standby Bus 2H since this is a Unit 2 issue. Notified: R4DO (Spitzberg).

ENS 4619120 August 2010 17:47:00South TexasNRC Region 4Automatic ScramWestinghouse PWR 4-LoopAt 1525 (hrs. CDT) on 08/20/10, Unit 1 experienced an automatic reactor trip while the plant was stable at 100% power in Mode 1. All systems actuated as designed. The reactor trip was caused by an inadvertent turbine trip signal initiated during testing. All ESF (Engineered Safety Features) systems actuated as designed. The following systems actuated: Auxiliary Feed Water and Feed Water Isolation. All control and shutdown rods fully inserted. The plant is currently stable at normal operating pressure and temperature with decay heat being removed via steam dumps to the condenser. No primary or secondary relief valves lifted during the transient. The plant is in its normal shutdown electrical lineup with no problems noted. The trip was uncomplicated. The turbine trip signal was generated by a human performance error during reactor trip breaker testing. The licensee has notified the NRC Resident Inspector.
ENS 4047323 January 2004 19:42:00South TexasNRC Region 4Automatic ScramWestinghouse PWR 4-LoopWe make the following report per 10CFR50.72(b)(2)(iv)(B). At 16:16 CST Unit 1 Reactor automatically tripped from full power due to (actual) high-high level in 1B Steam Generator. Prior to the trip, vital distribution panel 1201 lost power when it's normal power supply inverter failed. Steam Generators 1A and 1B levels were selected to instruments from this power supply (and therefore generating a false low level output). Operators were in the process of taking manual control of 1A and 1B Main Feed regulating valves when the Main Turbine trip was actuated due to the high level in 1B Steam Generator. A reactor trip occurred due to the Turbine Trip above 50% power. The unit is stable at 567 degrees and 2235 pslg. We also make the following report per 10CFR50.72(b)(3)(iv)(A). Following the reactor trip the Auxiliary Feed Water System automatically actuated on (actual) low steam generator level. This is normal for a trip in the Unit 1 from full power. The following information is also provided: All control rods fully inserted. No primary reliefs lifted. Technical Specification 3.8.3.1 action b was entered due to the vital distribution panel not being energized from its normal source. (inverter). It is currently power from it's voltage regulator. Decay heat is currently being removed via the steam dumps. The plant electrical system responded normally and all emergency diesel generators remain in standby. All ECCS systems remain operable. There are no primary to secondary leaks. The licensee notified the NRC Resident Inspector.