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| Start date | Title | Description | Topic | |
|---|---|---|---|---|
| ENS 54561 | 4 March 2020 13:18:00 | EN Revision Imported Date : 3/6/2020 NOTIFICATION TO OTHER GOVERNMENT AGENCY On March 4, 2020, an actual Unusual Event code was inadvertently sent to an offsite agency, Institute of Nuclear Power Operations (INPO), and to a former NRC Resident Inspector during a planned emergency response drill. The NRC Resident Inspector has been notified.
Based on further review of the NRC reporting guidance relative to these criteria, STP has concluded that this condition is below the reporting threshold outlined in NUREG-1022 Revision 3. NUREG-1022 states the following (page 54): 'Licensees generally do not have to report media and government interactions unless they are related to the radiological health and safety of the public or on-site personnel, or protection of the environment. The condition originally reported in EN 54561 is not a news release or government notification and has no impact on the radiological health and safety of the public or on-site personnel, or protection of the environment. Therefore, STP is retracting EN 54561. The NRC Resident Inspector was notified on 3/5/2020 at 1310 CST. Notified R4DO Rick Deese. | ||
| ENS 51536 | 13 November 2015 12:39:00 | Notification of Unusual Event Due to Unidentified Rcs Leakage Greater than 10 Gpm | While in Mode 3, South Texas Project Unit 1 declared an Unusual Event at 0639 CST on 11/13/15, due to SU7 of EAL1- Unidentified RCS or Pressure Boundary leakage greater than 10 gpm. The excessive leakage to the WHT (waste holding tank) occurred when a letdown system demineralizer was placed in service. Operators bypassed the demineralizer and the RCS leakage was stopped. The excess leakage lasted for approximately 8 minutes and the maximum leakage was estimated to be 12-15 gpm. There was no impact on South Texas Unit 2 which continues to operate at 100% power. South Texas Project Unit 1 exited the Unusual Event at 0802 CST on 11/13/15, after verifying Unidentified RCS leakage less than 1 gpm. The demineralizer drain valve was partially open and was the cause of the excess leakage. The drain valve has been closed. The licensee has notified the NRC Resident Inspectors. Notified DHS SWO, FEMA Ops Center, FEMA NWC, NICC Watch Officer, and NuclearSSA via email
Due to entering the STP (South Texas Project) Emergency Plan (Unusual Event), STP has officially determined to make a planned press release. Per 10 CFR 50.72(b)(2)(xi), STP is making a notification to the NRC via the emergency notification system (ENS). The NRC Resident Inspector has been notified of the press release. The planned press release shares the following information: On November 13, 2015, STP Nuclear Operating Station, Unit 1, declared an Unusual Event at 0639 CST. Plant operators identified increasing reactor coolant system leakage in Unit 1. Plant Operators took immediate actions to verify the source and safely isolate and stop the leakage. Upon identifying the source of the leakage, the Unusual Event was exited at 0802 CST on November 13, 2015. The leakage was captured and maintained within an on-site storage tank and there was no radioactive release to the environment. STP Unit 1 is preparing for restart following a scheduled refueling and maintenance outage. Notified the R4DO (Gaddy).
The purpose of this report is to retract the ENS report made in accordance with 10 CFR 50.72 (a)(1)(i) on November 13, 2015, at 08:21 EST (ENS # 51536). STP Nuclear Operating Company declared an Unusual Event at 0639 CDT on November 13, 2015, based on Initiating Condition for Reactor Coolant System (RCS) Leakage Emergency Action Level (EAL) SU7. The event was reported to the NRC under EN # 51536 and the event was subsequently terminated on November 13, 2015 at 0802 CST. After further review, the emergency declaration is being retracted because the source of the leakage was from the Chemical and Volume Control System (CVCS) and not from the RCS. The NRC Resident Inspector will be notified. Notified the R4DO (Hagar). | Pressure Boundary Leakage |
| ENS 48277 | 22 August 2012 17:36:00 | Missing Flood Seal | During flooding walkdowns being performed on August 22, 2012, with the unit at 100 percent power, South Texas Project Unit 2 discovered the potential for water intrusion into the 10' Elevation Electrical Auxiliary Building (EAB) via a 2-inch underground conduit that was found to be missing its flood seal. It has been determined that the missing flood seal compromised the external flood design controls for the EAB. If flooding of the 10 (foot) EAB were to occur as a result of the missing flood seal, the operability of the Train A Engineered Safety Features (ESF) switchgear and the ESF Sequencers for all three Standby Diesel Generators could have been affected. Additionally, the Qualified Display Parameter System process cabinets (which control Auxiliary Feedwater flow and Steam Generator PORVs) and the Auxiliary Shutdown Panel are also located on the 10' Elevation. Repairs have been made and the 2-inch conduit is sealed. The event is being reported under 10 CFR 50.72(b)(3)(ii)(B) for Unit 2 being in an unanalyzed condition that significantly degraded plant safety, and under 10 CFR 50.72(b)(3)(v) as an event or condition that could have prevented the fulfillment of a safety function. The NRC Resident Inspector has been notified.
The purpose of this call is to retract the notification made on 09/05/2012, Event Number 48277. Further analysis indicates that water intrusion resulting from the missing 2-inch conduit seal would not have been sufficient to affect the operability of the equipment located on the 10-foot elevation of the Unit 2 Electrical Auxiliary Building. It has been determined that the maximum water depth would not have exceeded 2 inches in depth and all safety related equipment on the 10-foot elevation is greater than 2 inches above the floor, therefore there would be no impact to any safety-related equipment. Accordingly, this event notification is being retracted. The licensee will notify the NRC Resident Inspector. Notified the R4DO (Geoffrey Miller). | Unanalyzed Condition |
| ENS 46146 | 3 August 2010 20:06:00 | Potential Safety System Functional Failure of the Accident Mitigating Function | On 8/3/10 South Texas Project Unit 2 was in a scheduled A Train work week with the following equipment inoperable for planned maintenance; Essential Cooling Water Pump, Essential Chiller, Component Cooling Water Pump, Engineered Safety Function (ESF) Diesel Generator (DG), High Head Safety Injection (HHSI) pump, Low Head Safety Injection (LHSI) pump, and Containment Spray (CS) pump. At 0754 (CDT) on 8/3/10 the B train sequencer trouble alarm was received. The immediate operability determination was the sequencer remained operable. It was later identified during testing that the sequencer was inoperable. The B train sequencer was declared inoperable at 1506 (CDT) on 8/3/10. Due to loss of the automatic load sequencing support function, all associated train B safety equipment that is sequenced on the B train 14.16 kv bus during a Mode 1 Safety Injection (SI) was also declared inoperable. This condition resulted in an inoperable condition on two out of three safety trains for the accident mitigating function including the A and B train HHSI, LHSI, and CS pumps. All C train safety injection pumps remained operable. Pending a formal operability determination, this is conservatively considered to be a safety system functional failure of the accident mitigating function. This was determined to be reportable within 8 hours as required by 10 CFR 50.72(b)(3)(v)(D). The B train trouble alarm, an auto test feature, was discovered by operators during their rounds. The licensee entered their configuration risk management plan within the 1 hour as required. Currently, the licensee is working on completing the scheduled A train maintenance and restoring operability sometime in the morning. Also, a work package is under development to repair the faulty B train sequencer. The risk based time limit for restoring operability requires completion by 0449 (CDT) on 8/8/10. Unit 1 is unaffected and continues to operate at 100% power. The licensee informed the NRC Resident Inspector.
The purpose of this update is to retract the notification made in ENS Report #46146 (August 3, 2010). Following the ENS notification, troubleshooting determined the cause of the Train B sequencer alarm to be the failure of an Output Mode I Actuation Timing Switch Module. An engineering evaluation of the event has been completed and determined that a failure of this module did not affect the ability of the ESF load sequencer to perform its design function. Therefore, the Train B sequencer and associated Train B ESF equipment remained technically operable during the time that Train A equipment was inoperable due to scheduled maintenance, and a condition reportable per 10 CFR 50.72(b)(3)(v) did not exist. The licensee will notify the NRC Resident Inspector." Notified R4DO (Walker). |