Manual Reactor Trip on Loss of Main Condenser Vacuum
At 1539 (CST) December 5, 2018, with Unit 1 at 100 percent power, the reactor was manually tripped due to degrading condenser vacuum. The trip was uncomplicated with all systems responding normally, post-trip. An actuation of the auxiliary feedwater system occurred during the manual trip. The auxiliary feedwater system automatically started as designed when the valid actuation signal was received. Operations stabilized the plant in mode 3 (hot standby). Decay heat is being removed by atmospheric dump valves.
Unit 2 is not affected.
This event is being reported pursuant to 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A).
The loss of condenser vacuum resulted because one of two circulating water pumps was running and its discharge valve shut. The cause for the valve shutting is under investigation. There is no primary to secondary leakage.
Actuation of Blackout Sequencers Due to Loss of One Offsite Power Source
At 0315 (CST) on 12/3/18, the Comanche Peak Nuclear Power Plant experienced a loss of 138 KV transformer XST1. Unit 1 is currently at 100% power. Unit 2 was subjected to actuation of both blackout sequencers causing an automatic start of both motor driven Auxiliary Feedwater (AFW) pumps as well as the turbine driven AFW pump.
No emergency diesel generators started as per design. Train A and B motor driven and the turbine driven AFW pumps have been returned to automatic. All other safety systems functioned per design.
The loss of power to 138 KV transformer XST1 resulted in loss of power to both safeguards busses on Unit 2. The busses performed a load-shed and slow transfer to power supplied from 345 KV transformer XST2A as designed and were re-energized and loads sequenced back onto the busses. The emergency diesel generators are not required to start unless the busses are not re-energized by the alternate offsite transformer. All electrical power related actuations functioned as designed. There was no impact on Unit 1.
The licensee has notified the NRC Resident Inspector."
Turkey Point Nuclear Generating Unit Nos. 3 and 4 - Issuance of Amendments Nos. 284 and 278 Regarding Adoption of Risk-Informed Completion Times in Technical Specifications (CAC Nos. MF5455 and MF5456; EPID L-2014-LLA-0002)
Automatic Reactor Trip of Unit 2 Due to a Load Rejection
At 1006 (PST), on December 1, 2018, with Unit 2 at 100 percent power, the reactor automatically tripped due to a load rejection from the 500 kV offsite electrical system.
Operations responded and stabilized the plant. Decay heat is being removed by the Main Steam system to the main condenser using the steam dump valves. The cause of the load rejection is currently under investigation.
Due to the Reactor Protection System actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). Additionally, due to the actuation of the Auxiliary Feedwater System, as expected, this event is being reported per 10 CFR 50.72(b)(3)(iv)(A).
There was no impact on the health and safety of the public or plant personnel. The NRC Senior Resident Inspector was notified. A press release is planned for this event.
All control rods fully inserted and the trip was uncomplicated. There was no effect on Unit 1.
Comanche Peak Nuclear Power Plant, Unit Nos. 1 and 2 - Issuance of Amendments 171 and 171 Regarding Revision to Technical Specifications for Engineered Safety Feature Actuation System Instrumentation (EPID L-2018-LLA-0081)
Seabrook Station, Unit No. 1 - Issuance of Amendment No. 158 Removing Requirement to Perform Certain Surveillance Requirements During Shutdown and Changes to Administrative Technical Specifications (EPID L-2017-LLA-0407)
Point Beach Nuclear Plant, Units 1 and 2 - Issuance of Amendments to Adopt Title 10 of Code of Federal Regulations 50.69, Risk Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors