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| Discovered date | Reporting criterion | Title | Description | LER | |
|---|---|---|---|---|---|
| ENS 40380 | 9 December 2003 21:38:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unable to Achieve Cold Shutdown Using Natural Circulation at a Cooldown Rate of 50 Degrees Per Hour | At 1538 on 12/09/03, it was determined that the plant could not achieve cold shutdown using Natural Circulation with the available volume of the Auxiliary Feed Water Storage Tank (AFWST) and at an allowed plant cooldown rate of 50 degrees F/hour. The plant has a functional objective to achieve Plant Shutdown from Operating Condition to Cold Shutdown Condition with the Natural Circulation Cooldown process with the volume of water available in the AFWST. Natural Circulation cooldown is required during Loss of Offsite Power (LOOP), long term cooling, Safety Grade Cold Shutdown and Appendix R type fire with LOOP. This condition also applies to Unit 2. STP (South Texas Project) changed from a Reactor Vessel Head (RVH) T-Hot Plant to a RVH T-Cold Plant after replacement of the plant's steam generators. As a result, the plant cooldown rate under natural circulation conditions was changed from 25 degrees F/hour to 50 degrees F/hour based on a Westinghouse evaluation. While performing confirmatory calculations to address a fire safe shutdown issue, it was determined that the plant can be cooled down with two steam generators using natural circulation. However, at a cooldown rate of 50 degrees F/hour, the two steam generators not being used for cooldown would stagnate with hot water in the primary side tubes. During the depressurization process, the hot water flashes to steam such that depressurization below approximately 1000 psig is significantly challenged. This results in filling the pressurizer and a loss of RCS pressure control. The fluid in the RCS (Reactor Coolant System) loops not receiving AFW will remain at saturated conditions until cooling is achieved by other means. Cooldown and depressurization of the RCS in this configuration will take substantially longer than assumed in the current analyses. Although there is adequate core cooling, the plant will be in a condition that is outside the existing design basis and not specifically addressed by the Emergency Operating Procedures. Therefore, this condition resulted in the plant being in an unanalyzed condition that significantly degraded plant safety. Thermal Hydraulic Analyses at a cooldown rate of 25 degrees F/hr demonstrated that natural circulation will occur in the two steam generators that are not being used for cooldown such that the stagnated hot water conditions would not occur in these steam generators. This would allow for depressurization of the reactor coolant system and successfully meet the functional objective. A compensatory action is in place to limit natural circulation cooldown rate to no greater than 25 degrees F/hr. The licensee has notified the NRC Resident Inspector. | |
| ENS 40473 | 23 January 2004 22:16:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Trip Due to High-High Steam Generator Level | We 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. | |
| ENS 40612 | 27 March 2004 04:30:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Regarding Hhsi Flush Line Isolation Valve Leakage - | While performing a High Head Safety Injection (HHSI) Train-B inservice test, a Plant Operator noted leakage coming through HHSI Flush Line Isolation Valve #SI-0120B. This valve is located on a flush line coming from the discharge of the HHSI pump and directs water to the Safety Injection Pump room sump located within the Fuel Handling Building. The operator investigated and determined that the leakage was due to the valve not being fully seated. The Licensee has come to the conclusion that the estimated leakage through the valve exceeded the allowable value to remain in compliance with 10 CFR 50, Appendix A, GDC 19 limits for Control Room Envelope during the post LOCA Containment recirc phase of a large break LOCA. This condition resulted in an unanalyzed condition that significantly degraded plant safety requiring a notification to the NRC within eight hours per 10 CFR 50.72 (b) (3) ii. Subsequently, flush line valve #SI-0120B has been fully seated, and the leakage stopped. The licensee considers this valve to be operable. The Licensee notified the NRC Resident Inspector. | |
| ENS 40657 | 8 April 2004 14:44:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification of a Fatality | The purpose of this report is to notify the NRC of a fatality involving a contract worker at the South Texas Project. Specifically, at 0810 (CDT), the South Texas Project Unit 1 Control Room was notified that an individual located outside of Unit 2 in a non-radiological area had lost consciousness. The site emergency medical team responded and an ambulance was requested at 0812. At 0836, the worker left the site in an ambulance. At 0944, South Texas Project was notified that the individual passed away at Matagorda General Hospital. This fatality was the result of a medical emergency and was not occupationally related. South Texas Project has notified OSHA of the fatality. A press release is not planned. The individual was a contractor working in a temporary tool storage area outside Unit 2. The Licensee notified the NRC Resident Inspector. | |
| ENS 41392 | 9 February 2005 18:22:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded | Technical Specification Required Shutdown Due to Unisolable Pressure Boundary Leak | The following information was obtained from the licensee via facsimile: On February 9, 2005, at 1222 hours (CST), South Texas Project Unit 2 commenced a reactor shutdown required by Technical Specification (TS) 3.4.6.2, 'Reactor Coolant System - Operational Leakage.' Following investigation into an increasing containment atmosphere particulate radiation monitor trend, primary leakage (steam plume) was discovered coming from a 3/4 inch vent line off of the 'A' Cold Leg Safety Injection line. The leak is located in an area between the Safety Injection line and the first vent line isolation valve, and is therefore considered an unisolable pressure boundary leak. TS 3.4.6.2 requires that with any Pressure Boundary Leakage, the Unit must be in at least Hot Standby within 6 hours and in Cold Shutdown within the following 30 hours. At the time of discovery, the total unidentified reactor coolant system leak rate was determined to be 0.13 gpm. The vent line pipe and weld material is stainless steel. This notification is being made in accordance with 10 CFR 50.72 (b)(2)(i) for commencement of a TS required shutdown, and 10 CFR 50.72 (b)(3)(ii)(A) for the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded. There is no impact on South Texas Project Unit 1. The licensee has notified the NRC Resident Inspector. | |
| ENS 41394 | 10 February 2005 02:20:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Press Release for Plant Shutdown | The following information was obtained from the licensee via facsimile: STP (South Texas Project) Nuclear Operating Co. will be making a press release concerning the shut down of Unit 2. STPNOC will be sharing the press release with various locals and state government agencies and the media. NRC was notified of the TS (Technical Specification) required shutdown on 2/9/05 (EN# 41392) The licensee has notified the NRC Resident Inspector.
STP Nuclear Operating Company (STPNOC) issued a press release at 1503 today concerning the status of the shutdown of Unit 2. STPNOC has shared the press release with various local and state government agencies and the media. NRC was notified of the Technical Specification required shutdown on 2/9/05 (Reference EN# 41392). The licensee informed the NRC Resident Inspector. Notified R4DO (Blair Spitzberg). | |
| ENS 41505 | 19 March 2005 14:27:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Injured Contract Employee | The following information was obtained from the licensee via facsimile (licensee text in quotes): South Texas Project Nuclear Operating Company has been in contact with various news agencies following an industrial accident that occurred at 0827 this morning. A contract employee fell approximately eight to ten feet while descending a permanent plant ladder on a structure in the secondary plant. The individual sustained injuries to his head and back, and has been transported to Herman Hospital in Houston, TX by a Life Flight Helicopter. The NRC Regional Office has been informed. The individual was conscious and in stable condition when he left the facility. The licensee notified the NRC Resident Inspector. | |
| ENS 41803 | 17 May 2005 21:02:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid System Actuation - Auxiliary Feedwater Pump Started During Surveillance | Per 10 CFR 50.73(a)(1), this telephone notification is made under 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation. The train D steam-driven Auxiliary Feedwater Pump was inadvertently started while performing post-maintenance testing on another component. The test was conducted using applicable steps in a surveillance procedure for the solid state protection system. A procedure step for isolating the auxiliary feedwater pump steam turbine was incorrectly performed so that the steam turbine was not isolated, as intended, and started when the test actuation signal was initiated. The steam-driven turbine and pump functioned successfully as a result of the invalid signal. The signal was determined to be invalid in that it was not initiated in response to actual plant conditions or parameters satisfying the requirements for initiation of the safety function of the system. The pump start was not an intentional manual initiation. The invalid actuation is reportable in that it did not occur while the system was properly removed from service and did not occur after the safety function had already been completed The licensee notified the NRC Resident Inspector. | |
| ENS 42322 | 8 February 2006 22:30:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification | Notification is being made that the South Texas Project is notifying the State of Texas Department of State Health Services not to use the Delta Temperature method (primary method) (used to determine atmosphere stability input to offsite dose assessment calculations) for dose assessment. South Texas Project will be using the Backup method until the Delta Temperature problems are resolved. The licensee notified the NRC Resident Inspector. | |
| ENS 42579 | 16 May 2006 14:45:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Disruption of Incoming and Outgoing Telephone Communciation Capability | On 05/16/2006 at 0945 CDT, the control room was notified that problems with Bell South and Verizon phone services had occurred which disrupted incoming and outgoing telephone communications capability for both Unit 1 and Unit 2. Subsequent attempts from the control room confirmed that the State and County ringdown line was dead as well as the Emergency Notification System line. It was also determined that although outgoing calls from the control room and Emergency Operations Facility via land line were possible, incoming calls could not be received. The NRC Operations Center was contacted via land line at 09:50 CDT to inform the NRC of the issue. Alternate communication via cell phone and satellite phone was established to allow incoming calls from the NRC, State and County. The NRC Senior Resident Inspector was notified of the issue. Telephone service was restored at 13:50 CDT which re-established all normal and emergency telephone communications capability. | |
| ENS 42757 | 8 August 2006 20:43:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Inadvertent Emergency Notification Siren Activation | At approximately 15:43 (CDT) on 8/8/2006, all STP Emergency Notification System (ENS) sirens inadvertently/spuriously activated. The sirens automatically secured after approximately 3 minutes. All sirens except one at El Maton have subsequently been polled operable. STPNOC is investigating the cause of the activation. STPNOC has notified Matagorda County Sheriff Department and radio station KZRC. Inquiries from the public have been received. This notification is being made under 10CFR50.72(b)(2)(xi) as an event where other government agencies were notified. The licensee notified the NRC Resident Inspector. | |
| ENS 42924 | 21 October 2006 20:58:00 | 10 CFR 50.72(b)(3)(xii), Transport of a Contaminated Person Offsite | Offsite Medical Treatment of Potentially Contaminated Contract Employee | A contract employee experienced heat exhaustion while working in the Reactor Containment Building in a contaminated area and was considered potentially contaminated because the initial survey for radioactive contamination had not been completed prior to transporting the employee offsite for medical treatment. The licensee notified the NRC Resident Inspector.
At 1758 CDT on 10/21/06, the licensee was notified by their Health Physics Dept. that the contract employee was transported to the Matagorda Hospital in Bay City, TX and was found not to be contaminated. Additionally, all instruments and equipment used in the incident were surveyed and no contamination was found. The licensee notified the NRC Resident Inspector. Notified R4 DO (D. Powers). | |
| ENS 43086 | 10 January 2007 18:35:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Offsite Landline Communications Capability Due to Cut Fiber Optic Cable | On 01/10/2007 at 1235 CST, the Unit 1 control room was notified that the offsite fiber cable from Palacios to Port Lavaca was cut at approximately 1155 hours by a building contractor just out of Palacios on Texas Highway 35. Verizon dispatched a crew to repair. Estimated time for repair is about 4 hours. Offsite communications is lost from both Unit 1 and Unit 2 control rooms including the state and county ring down lines, the NRC ring down line and the ability to transfer information from the Emergency Response Data System (ERDS) to offsite agencies. Satellite phones remain available. At 1258 CST, the NRC Operations Center was notified via satellite communications of alternate phone numbers to contact the Unit 1 and Unit 2 Control Rooms. This is a follow-up to make the notification of this event to the NRC pursuant to 10 CFR 50.72 (b)(3)(xiii). The NRC Senior Resident Inspector was notified of this issue.
All offsite lines have been restored as of 1716 CST on 01/10/07. The licensee informed the NRC Resident Inspector. Notified R4DO (Spitzberg). | |
| ENS 43595 | 25 August 2007 12:30:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Erds System and Portions of Plant Computer Out of Service for Planned Maintenance Outage | The licensee will perform a planned power outage on Unit 1 which will take the ERDS system, 25% of the control room annunciators, and portions of the plant computer out of service. Some points on the plant computer will not be able to be monitored during the outage. However, the licensee has compensatory measures in place to monitor those parameters on the control boards. The outage is scheduled from 0730 CDT until 1800 CDT. The licensee will enter Technical Specification LCO 3.1.3.1 and 3.1.3.2. The licensee notified the NRC Resident Inspector.
The licensee restored ERDS to service at 1805 CDT on 8/25/07 and will inform the NRC Resident Inspector. Notified R4DO (Jeff Clark). | |
| ENS 43612 | 1 September 2007 21:58:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Related to Fatality | The purpose of this report is to notify the NRC of a fatality involving a contract worker at the South Texas Project. Specifically, at 15:35 (CST), the South Texas Project Unit 1 Control Room was notified that an individual located outside of the protected area but in the owner controlled area had loss consciousness. The site emergency medical team responded and an ambulance was requested at 15:39. At 16:58 the South Texas project was notified that the individual was pronounced dead upon arrival at Matagorda General Hospital. The South Texas Project will be notifying OSHA of the fatality. A press release is not planned at this time, but is under consideration. The resident NRC inspector has been notified | |
| ENS 44605 | 26 October 2008 04:42:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Valid Safety Injection Signal Due to Maintenance Error | At approximately 2342 on 10/25/2006, while performing maintenance on the solid state protection system in Mode 5 cold shutdown, Unit 2 received an automatic safety injection signal which resulted in all three ESF Diesel Generators starting and a containment ventilation isolation and containment phase A isolation. All safety injection pumps were in pull-to-lock per plant conditions so that the pumps did not start and no water was discharged into the reactor coolant system. As a result, the ESF Diesel Generators started but did not load as designed. The residual heat removal pumps were stripped from the ESF electrical busses due to the actuation. The first residual heat removal pump was restored within 4 minutes upon the loss of residual heat removal cooling and the second pump was restored within 6 minutes. The residual heat removal system heat exchangers were bypassed at the time of the event and the plant was being allowed to heat up. The cause of the automatic safety injection signal was an inadvertent removal of the block for the low pressurizer pressure safety injection system during the maintenance. Therefore, the signal was a valid signal initiated in response to a parameter satisfying the requirements for initiation of the safety function of the system. Although the actuation was the result of a valid signal, safety injection was not required in this Cold Shutdown Mode of Operation. This notification is being made under 10CFR50.72(b)(3)(iv) as an event that results in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B) of this section. This actuation was initially determined to be due to an invalid signal. Upon further review, it was determined at 1745 on 10/27/08 that the actuation was due of a valid signal. The licensee notified the NRC Resident Inspector. | |
| ENS 45262 | 13 August 2009 20:41:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to a Grass Fire in the Owner Controlled Area | A fire was reported to the unit-2 control room at 1541 Central time (CDT). The fire was reported in the Owner Controlled Area. Local (Bay City) fire department was dispatched to fight the fire. The fire occupied approximately 2 acres. The fire was reported to be under control at 1635 (CDT). No plant equipment was damaged nor was the operations of the unit affected. Region 12 of the Texas Commission of Environmental Quality was notified at 1721 (CDT) and no further actions were required by the Agency (Texas Department of Environmental Quality). The licensee notified the NRC Resident Inspector. | |
| ENS 45631 | 8 July 2008 03:47:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Loss of Fire Suppression Capability | This is an 8-hour notification being made in accordance with 10CFR 50.72(b)(3)(ii)(B) for an event or condition that results in the plant being in an unanalyzed condition that significantly degrades plant safety. This notification is being made as the result of the re-review of a July 7, 2008 occurrence which resulted in an inadvertent isolation of a large portion of the (fire suppression) ring header affecting all Unit 2 fire suppression and a portion of Unit 1 fire suppression. The Unit 1 ring header isolation did not have an affect on the fire safe shutdown capability of Unit 1. However, three areas in Unit 2 which credit the availability of fire suppression to assure that the safe shutdown capability could have been achieved did not have fire suppression for approximately 3 hours. A Licensee Event Report will be submitted within 60 days. The licensee notified the NRC Resident Inspector. | 05000499/LER-2010-002 |
| ENS 45675 | 3 February 2010 19:44:00 | 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | Technical Specification Shutdown Required Due to Control Rod Out of Alignment | A shutdown of South Texas Project Unit 1 was initiated at 13:44 hours (CST) on February 3, 2010. When in Action b.2. of Technical Specification (TS) 3.1.3.1, 'Moveable Control Assemblies Group Height,' a second control rod, B-12, in Shutdown Bank A was declared inoperable when the rod came out of alignment with the remainder of the rods within its bank. The second control rod came out of alignment during the performance of Surveillance Requirement 4.1.3.1.2; a surveillance to determine operability by movement of the rod. For the above condition, Action c. of TS 3.1.3.1 was entered. When the requirements of the action could not be met, South Texas Project Unit 1 entered TS 3.0.3. and a plant shutdown was initiated. Prior to initiation of this event, South Texas Project Unit 1 was in Action b.2 (of TS 3.1.3.1) with rod C-5 of Shutdown Bank D trippable but inoperable due to causes other than addressed by Action a. The inoperable rod, C-5, was aligned within 12 steps of the remainder of the rods within its group and the rod sequence and insertion limits as specified in the Core Operating Limits Report were being maintained. At the time of this report, South Texas Project Unit 1 was at 30% power and decreasing. The plant will enter Mode 3, Hot Shutdown, at approximately 1800 CST. Shutdown was initiated when rod B-12 could not be aligned within 12 steps of the remainder of rods within its bank as specified in Action c. of TS 3.1.3.1. The licensee has notified the NRC Resident Inspector.
At 1730 (CST) during performance of the Unit 1 shutdown, control rod H-2 in Bank 1C inserted from 246 steps, as indicated by the digital rod-position indication system, to 234 steps indicated without a demand signal applied to the control bank. The group step counter remained at 249 steps with no other rods in Bank 1C indicating movement. The shutdown continued normally from that point. Control rod H-2 stepped with the rest on the rods in the bank down to zero steps. All control rods in Unit 1 are at zero steps. The shutdown rods are currently withdrawn. The licensee has notified the NRC Resident Inspector. Notified R4DO (Gaddy).
This update corrects information provided earlier at 2230 EST on February 3, 2010 after reviewing post shutdown data. During the performance of the Unit 1 shutdown, control rod H-2 in Bank 1C inserted upon demand, as indicated by the digital rod-position indication system, but did not withdraw upon demand, as indicated. This occurred when controlling Bank 1C between 249 and 242 steps by alternating insertion and withdrawal demand signals to control reactivity. At approximately 1731, the shutdown continued normally from that point. Control rod H-2 stepped in with the rest of the rods in the bank down to zero steps. All control rods and shutdown rods in Unit 1 were subsequently driven in to zero step position. The licensee notified the NRC Resident Inspector. Notified R4DO (Gaddy). | |
| ENS 46146 | 3 August 2010 20:06:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | 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). | |
| ENS 46191 | 20 August 2010 20:25:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Trip Due to an Inadvertent Turbine Trip Signal During Testing | At 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 46298 | 1 October 2010 00:04:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Standby Diesel Generator Autostart Due to Loss of a Switchyard Bus During Maintenance | At 1904 (CDT) on 9/30/2010, the South Texas Project (STP) North switchyard bus was lost due to a Transmission & Distribution Service Provider (TDSP) human performance error that occurred while performing maintenance on breaker Y-0530. This resulted in a loss of power to Standby transformer 1 which was supplying power to the Unit 1 B Train Engineered Safety Features (ESF) 4160v bus. The B Train Standby Diesel Generator automatically started due to the Loss of Offsite Power (LOOP) on its associated bus. The Mode II (LOOP) ESF loads sequenced onto the bus. All safety related equipment responded as expected. Action (e) of Technical Specification (TS) 3.8.1.1, 'AC Electrical Power Sources', was momentarily entered due to the loss of two independent offsite circuits while the North bus was de-energized. The North bus was de-energized for approximately 5 minutes. Action (a) of Technical specification (TS) 3.8.1.1, 'AC Electrical Power Sources', was entered due to the loss of one independent offsite circuit. All Technical Specification Limiting Condition of operation have been exited at this time. An 8-hour notification is required for this event due to the valid actuation of safety related equipment as described in 10CFR50.72 (b) (3) (iv) (A). (A notification is required for) any event or condition that results in valid actuation of any of the systems listed in paragraph (b) (3) (iv) (B) of this section, except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation. The NRC Resident Inspector has been notified. Unit 2 briefly entered a Technical Specification Limiting Condition of Operation, while all electrical buses remained energized. | |
| ENS 46387 | 3 November 2010 15:21:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(a)(1)(i), Emergency Class Declaration 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unusual Event Declared Due to an Explosion in the Protected Area Which Affects Normal Operations | 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.
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)
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 46588 | 2 February 2011 14:30:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Partial Loss of Prompt Notification System (Pns) Emergency Sirens Due to a Loss of Power | At approximately 0830 (CST) on 2/2/2011, eleven (11) of thirty-two (32) STP Prompt Notification System (PNS) sirens were not operable due to loss of power. The sirens were subsequently polled at approximately 0909 (CST) and all sirens except 3 were operable. The loss of power was caused by rolling outages due to unusually severe cold weather. ERCOT issued an order requiring load shedding to maintain a steady state system frequency of 59.8 Hertz (Hz) on the grid. The outages were suspended at 1400 hrs but rolling outages could continue through the end of the week potentially affecting the sirens. All 32 sirens were likely affected during the outages for some un-quantified period of time. Continuous polling of the sirens was not performed or advisable since polling depletes the batteries which could affect the operability of the sirens. STPNOC (South Texas Project Nuclear Operating Company) has notified Matagorda County Sheriff Department. Compensatory measures have been verified to be available should the Prompt Notification System be needed. This consists of using Local Law Enforcement Personnel for 'Route Alerting' of the affected areas of the Emergency Planning Zone (EPZ). Matagorda County Emergency Management has verified that the Matagorda County Sheriffs Department is on standby for Route Alerting. STPNOC is currently transitioning to new sirens. While the new sirens are not currently credited in the STP Emergency Plan, we have received final FEMA approval. All of the new battery-backed sirens were tested and verified to remain operable and capable of notifying the population in the EPZ. This notification is being made under 10 CFR 50.72(b)(3)(xiii) due to a significant loss of the offsite Prompt Notification System. It is possible that rolling outages may recommence in the next several days. The licensee informed the NRC Resident Inspector and the offsite agencies identified above. | |
| ENS 46721 | 4 April 2011 07:24:00 | 10 CFR 50.72(b)(3)(xii), Transport of a Contaminated Person Offsite | Transport of Contaminated Injured Person to an Offsite Facility | On 4/4/11, South Texas Project Unit 1 was in a scheduled refueling outage with workers performing activities in the Reactor Containment Building (RCB). At 0224 (CDT), the Unit 1 control room received a report of an individual in the reactor cavity with a medical emergency. An ambulance left the site at 0400 (CDT) on 4/4/11 to transport the contaminated individual to the Matagorda Regional Medical Center. The individual was decontaminated at Matagorda Regional Medical Center. It was determined that the contamination levels on the individual were low with 400 - 500 cpm on clothing and 1200 cpm in the individual's hand. There was no spread of contamination in either the ambulance or at the hospital. This was determined to be reportable within 8 hours as required by 10 CFR 50.72(b)(3)(xii). Site Health Physics personnel accompanied the injured individual in the site-owned ambulance. Decontamination was performed by the South Texas HP technicians. The licensee has notified the NRC Resident Inspector. | |
| ENS 47210 | 28 August 2011 01:30:00 | 10 CFR 50.73(a)(1), Submit an LER | Invalid Automatic Actuation of an Emergency Diesel Generator | At 2130 (EDT) on August 27, 2011, an automatic actuation of the Unit 1 Train A emergency diesel generator occurred due to an actuation signal from the load sequencer. The Train A 4160 kV emergency bus transferred to the emergency diesel generator and all Train A emergency loads required for Mode 2 started and sequenced onto the Train A 4160 KV emergency bus except the 480 volt center breaker to the bus E1A2 that did not close. The load sequencer is designed upon the receipt of a safety injection actuation and/or loss of offsite power to provide a signal to strip loads from the 4160 kV emergency bus and then, in sequence, to re-energize the associated 480 volt buses and to load engineering safety feature components onto the 4160 kV and associated 480 volt emergency buses in a predetermined sequence. Per 10 CFR 50.72(b)(3)(iv)(B), additional emergency safety features loads that actuated were the Train A reactor containment fan coolers and auxiliary feedwater system. Unit 1 remains critical at 100 percent power. No emergency core cooling system injection occurred into the reactor coolant system. The event occurred during surveillance testing when the Train A sequencer was taken from the AUTO Test position to the local position. It is not understood why the actuation occurred. In addition, it is not understood why the 480 volt load center breaker to the bus E1A2 did not close. The 480 volt bus E1A2 was re-energized at 2308 (EDT) on August 27, 2011. The Train A 4160 kV bus was restored to the offsite power source at 0150 (EDT) on August 28, 2011 and the Train A emergency diesel generator and engineering safety features loads were restored to their normal condition at 0201 (EDT) on August 28, 2011. With the Train A sequencer non-functional, the following Train A components are inoperable: 1) High Head Safety Injection Pump 1A; 2) Low Head Safety Injection Pump 1A; 3) Containment Spray Pump 1A; 4) RCFC (Reactor Containment Fan Cooler) Fan 11A; 5) RCFC Fan 12A; 6) Component Cooling Water Pump 1A; 7) Essential Cooling Water Pump 1A; 8) Aux Feedwater Pump 11; 9) Control Room/Elect. Aux Bldg HVAC; 10) Ess (Essential) Chiller 12A; and 11) ESF Diesel Generator 11. Although these components will not automatically start on a safety injection signal or loss of offsite power, these loads can be manually actuated. Engineered Safety Features Trains B and C remain operable. The licensee notified the NRC Resident Inspector.
The licensee is updating this event report to retract the originally reported valid specified system actuation and report it instead as a 60-day invalid specified system actuation report made by telephone: This update is a 60-day telephone notification in lieu of a written licensee event report being made under 10CFR50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1). This event was originally reported per 50.72(b)(3)(iv)(A) as a valid actuation of the Unit 1 Train A emergency diesel generator and sequencing of Mode II (Loss of Offsite Power) emergency loads. The actuation occurred during surveillance testing when the Train A load sequencer was taken from the AUTO test position to the local position. Subsequent investigation has determined that the actuation occurred due to a faulty integrated chip within the sequencer's load sequence auto test module, and was not due to sensed or simulated plant conditions that would require a Mode II actuation. Unit 1 was at 100% power and no loss of offsite power occurred. The Train A equipment response to this invalid actuation is described in the original notification information provided on 08/28/2011. Additionally, the 10CFR50.72 Notification originally reported under Event Number 47210 is being retracted, since the actuation has been determined to be not valid. The licensee will notify the NRC Resident Inspector. R4DO (Whitten) notified. | |
| ENS 47362 | 20 October 2011 21:50:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to the Offsite Fatality of an Employee | On October 20, 2011 at approximately 1335 hours, a South Texas Project employee suffered an apparent heart attack offsite while attending a fire brigade training exercise. The person was transported to Matagorda County Regional hospital. The individual was evaluated by emergency room personnel and later pronounced deceased. OSHA is being notified pursuant to the requirements of 29CFR1904.39. This ENS report is being made in accordance with 50.72(b)(2)(xi). There was no radioactive contamination involved in this event. The licensee does not plan any media or press release. The NRC Resident Inspector has been notified. | |
| ENS 47485 | 29 November 2011 09:29:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Trip Due to Turbine Trip on Generator Lockout | 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.
The licensee has issued a press release concerning this event. The NRC Resident Inspector will be notified. R4DO (Farnholtz) informed. | |
| ENS 47491 | 20 November 2011 11:46:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Turbine Trip Protection Disabled While in Mode 3 | On November 20, 2011 at 0546 hours (CST), STP Unit 2 transitioned modes from Mode 4 to Mode 3. Prior to the mode change, all Solid State Protection System (SSPS) generated turbine trip signals were defeated by a maintenance work activity that installed a jumper in both channels (Train R and S) of non-class relays to the turbine trip circuit. The SSPS signals to the non-class relays that were defeated by the jumpers included the turbine trip from reactor trip breakers open (P4), turbine trip from a reactor trip signal (P-16), and the turbine trip from Steam Generator HI- HI (P-14). T.S. 3.3.2 Items 5a (P4) and 5b (P-14) are required in Modes 1, 2, and 3. The jumpers were removed around 0930 on November 20, 2011 with U2 still in Mode 3. Both the UFSAR and TS bases identify that the turbine trip mitigates the consequences of an accident. The TS bases states that an ESFAS initiated turbine trip mitigates the consequences of a steam line break or loss of coolant accident. The accident analysis for SGTR also assumes a turbine trip on a reactor trip to isolate the steam path. Although Unit 2 was in Mode 3, with the reactor trip breakers open, and turbine throttle valves closed while the jumpers were installed, this condition is conservatively considered to be a safety system functional failure. If not corrected, this condition could have prevented the fulfillment of the accident mitigating and control of the release of radiation safety functions. A review of the performance of this activity in previous outages was conducted. It was identified that during 2RE14 in April of 2010, a work package for this activity was not closed until after Mode 3. The 60 day LER will address if the jumpers were installed in Mode 3 in April, 2010. This was determined to be reportable within 8 hours as required by 10 CFR 50.72(b)(3)(v) parts (C) and (D). The licensee did not determine the reportability of this event until 1415 CST on 11/30/11. The licensee has notified the NRC Resident Inspector. | |
| ENS 48277 | 22 August 2012 17:36:00 | 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | 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). | |
| ENS 48448 | 27 October 2012 19:15:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Offsite Communications | On 10/27/2012 at 1415 CDT, the control room was notified of a loss of telephone communications. Reason is unknown at this time. Offsite communications lost includes the state and county ring down lines, the NRC ring down line. The ability to transfer information from the Emergency Response Data System (ERDS) to offsite agencies is believed not to be available. Satellite phones remain available. At approximately 1500 CDT, the NRC Operations Center was notified via satellite communications of alternate phone numbers to contact the Unit 1 Control Room and that Unit 2 Control Room satellite phone is not available to receive calls. This is a follow up to make the notification of this event to the NRC pursuant 10 CFR 50.72(b)(3)(xiii). The NRC Senior Resident Inspector was notified of the issue." State and local agencies were notified via alternate means.
Emergency Notification System has been returned to service. The cause of the loss of communications was a cut fiber optic line. Notified R4DO (Hagar). | |
| ENS 48651 | 4 January 2013 15:41:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unit 2 Manually Tripped After Two Shutdown Control Rods Unexpectedly Dropped During Surveillance Testing | On 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 48659 | 8 January 2013 22:40:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(a)(1)(i), Emergency Class Declaration 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Unusual Event Declared Due to Main Transformer Fire | 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.
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 49490 | 31 October 2013 22:12:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Postulated Fire Event Could Result in a Hot Short That Could Adversely Impact Safe Shutdown Equipment | While performing a review of industry OE (operating experience) concerning unfused ammeter circuits on station batteries, it was discovered that the ammeter circuits for all of the non-1E batteries are of a similar design to that described in the OE. Also, while reviewing additional DC circuits, it was discovered that the control circuit for the Turbine Generator Emergency Lube Oil pump is unfused, protected only by the motor circuit breaker with a trip setting of 350 amps. The concern is that under the fire safe shutdown rules it is postulated that a fire in one fire area can damage these circuits and cause short circuits without protection that would overheat the cables and possibly result in secondary fires in other fire areas where the cables are routed. The secondary fires could adversely affect safe shutdown equipment and potentially cause the loss of the ability to conduct a safe shutdown as required by 10CFR50 Appendix R. This condition is being reported in accordance with 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition that significantly degrades plant safety. Compensatory measures (fire watches) have been implemented for affected areas of the plant. The NRC Resident Inspector has been notified. | 05000289/LER-2014-001 05000498/LER-2013-003 |
| ENS 49666 | 20 December 2013 04:33:00 | 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Valid Actuation of Main Steam Isolation Valves That Was Not Part of a Preplanned Sequence | While in Mode 3 in preparing the Unit 2 secondary plant for startup, conditions occurred where it became necessary to break vacuum on the main condenser. Procedures directed closing of the main steam isolation valves. Instead of shutting each main steam isolation valve individually, a manual main steam isolation actuation was initiated through the solid state protection system (SSPS) to close the valves. This actuation of SSPS was a valid signal. The actuation was not part of a preplanned sequence. This notification is supported by the guidance of NUREG-1022, Revision 3, 'Event Reporting Guidelines 10CFR50.72 and 50.73.' In part, the guidance states: 'The Commission is interested in both events in which a system was needed to mitigate the consequences of an event (whether or not the equipment performed properly) and events in which a system actuated unnecessarily.' The manual actuation was not initiated to mitigate the consequences of an actual event. However, the method of closing the main steam valves for this condition did not specifically require that the valves should be closed by initiating a main steam isolation signal and therefore, the safety system was unnecessarily actuated. Therefore, this notification is being made pursuant to 10 CFR 50.72(b)(3)(iv)(A) as an event or condition that results in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B) that was not part of preplanned sequence during testing or reactor operation. The system listed in paragraph (b)(3)(iv)(B) is (2) main steam isolation valves. The licensee notified the NRC Resident Inspector. | |
| ENS 49740 | 18 January 2014 10:01:00 | 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | Unusual Event Due to Fire in the Protected Area | At 0346 CST (the Unit 1 control room) received a fire alarm in the plant computer room. Upon investigation (the licensee) discovered (the plant computer) room with heavy smoke present and the halon system actuated. (Plant operators) entered '0P0P04-ZO-0008, Fire and Explosion'. Entered Unusual Event at 0401 CST. Fire brigade present at Unit 1 electrical auxiliary building. At 0412 CST the fire was declared to be under control with no visible signs of flame noticed by the fire brigade. Unusual Event based on HU2 (fire or explosion) in the (Protected Area or Switchyard) which affects normal plant operations." At 0446 CST the fire was declared to be extinguished. No plant equipment or indications were affected. The licensee has notified the NRC Resident Inspector, the State of Texas, and other local authorities. Notified DHS SWO, FEMA Operations Center, NICC Watch Officer, and NuclearSSA via e-mail.
At 0957 EST, (on 1/18/14, the) Unusual Event (was) terminated. Fire damage assessment not complete. Working with site engineering, fire protection, and maintenance personnel to restore all fire detection and protection systems. Continuous fire watch being maintained. Priority is to restore fire detection and protection systems to affected area, followed by repairs to damaged equipment. The licensee has notified the NRC Resident Inspector, the State of Texas, and other local authorities. Notified R4DO (Keller), NRR (Uhle), R4RA (Dapas), NRR EO (Lee), and IRD MOC (Grant). Notified DHS SWO, FEMA Operations Center, NICC Watch Officer, and NuclearSSA via e-mail. | |
| ENS 50716 | 5 January 2015 23:45:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Death of Employee | At approximately 1545 CST on 1/5/15, an employee was found unconscious by fellow teammates. His teammates, who are certified in cardiopulmonary resuscitation (CPR), commenced resuscitation until Matagorda County EMS arrived on the scene and transported the individual to Matagorda County Regional Hospital for medical treatment. The individual was evaluated by the Emergency Room Physician and was later pronounced deceased due to Cardiopulmonary Arrest. STP is investigating the incident. STP has reported this to the Occupational Safety and Health Administration (OSHA) and as such is reporting this in accordance with 10 CFR 50.72 (b)(2)(xi). A press release is not planned at this time. The NRC Resident Inspector was notified. | |
| ENS 51073 | 15 May 2015 22:53:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Inadvertent Siren Actuation | A South Texas Project Offsite Emergency Notification siren was (inadvertently) going off. The Matagorda County Sheriff's office notified the Emergency Response organization at the station that a siren had actuated during a severe thunderstorm moving through the area. Station personnel are addressing the issue with the siren. The Matagorda County Sheriffs office was the only offsite agency that was contacted during this event. The licensee notified the NRC Resident Inspector. | |
| ENS 51115 | 1 June 2015 15:26:00 | 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | Loss of Unit 2 Ventilation Radiation Monitor Operability | On June 2, 2015 at 2027 CDT, it was discovered that the unit vent radiation monitor was inoperable beginning on June 1, 2015 at 1026 CDT. Compensatory measures were not taken in accordance with the Offsite Dose Calculation Manual (ODCM) during this time period and the radiation monitor was unable to be used to assess Emergency Action Levels in accordance with the Emergency Plan. On June 3, 2015 it was recognized that because no compensatory measures were implemented during the period of inoperability that the condition resulted in a major loss of emergency assessment capability which is reportable under 10CFR50.72(b)(3)(xiii). Compensatory measures were implemented per the ODCM upon discovery on June 2 at 2027, thus there is currently no major loss of emergency assessment capability. This event did not result in any challenges to the fission product barriers and it did not adversely affect the safe operation of the plant or the health and safety of the public. The NRC Resident Inspector will be notified. | |
| ENS 51339 | 23 August 2015 18:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Grass Fire in Owner Controlled Area | A fire was reported to the unit 2 control room at 1300 central time (CDT). The fire was reported to be in the owner controlled area 3/4 of a mile west of the protected area and switchyard. The local fire department was dispatched to fight the fire. The fire burned approximately 1.5 acres. The fire was reported to be out at 1417 central time. No plant equipment was damaged and the operation of the plant was not affected. Region 12 (Houston) of the Texas Commission of Environmental Quality (TCEQ) was notified of the event at 1509 for visible emissions resulting from the grass fire. No further actions are required by the TCEQ at this time and no press release is planned. The fire was caused by a downed 12.5 kV power line which powers outlying plant areas. The licensee notified the NRC Resident Inspector. | |
| ENS 51536 | 13 November 2015 12:39:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(a)(1)(i), Emergency Class Declaration | 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). | |
| ENS 51615 | 21 December 2015 21:33:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Trip Due to Feedwater Isolation | At 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 51687 | 27 January 2016 05:25:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Manual Reactor Trip Due to Loss of Feedwater to a Single Steam Generator | 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 51787 | 14 March 2016 07:47:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to Inadvertent Actuation of Offsite Emergency Notification Siren | A South Texas Project, Offsite Emergency Notification Siren, was inadvertently going off. The Matagorda County Sheriff's Office notified Site Security that a siren had actuated for no apparent reason. Station personnel are addressing the issue with the siren. The Matagorda County Sheriff's Office was the only offsite agency that was contacted during the event. The siren was tested and is considered functional at this time. Additional testing will be completed during daylight hours. The licensee will notify the NRC Resident Inspector. | |
| ENS 51897 | 2 May 2016 01:21:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | Automatic Reactor Trip Due to Generator Lockout | At 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 51964 | 28 May 2016 01:46:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Offsite Notification Due to an Inadvertent Actuation of One Emergency Siren | A South Texas Project offsite emergency notification siren was inadvertently going off. The Matagorda County Sheriff's Office notified Site Security that a siren had actuated. At the time of the inadvertent siren actuation the area was experiencing lightning and rain. Suspect lightning caused the inadvertent siren actuation. Station Personnel are addressing the issue with the siren. The Matagorda County Sheriff's Office was the only offsite agency that was contacted during the event. The licensee has notified the NRC Resident Inspector. | |
| ENS 52106 | 13 July 2016 16:00:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Exercise Press Releases Aired on Radio as an Actual Event | During the planned NRC/FEMA evaluated drill exercise on 7/13/16, two press releases written in the Joint Information Center (JIC) were published in the Public Information and Emergency Response (PIER) system without 'THIS IS A DRILL' denoted at the top of the page. The original press release was stamped with 'THIS IS A DRILL' at the top of page 1 and at the bottom of page 2. When it was added into the PIER system for publication/faxing, it was not noticed the top of the document denoting 'THIS IS A DRILL' was cut off. The local radio station affiliate was not aware of STP's (South Texas Project's) exercise on 7/13/16. As a result, the affiliate station thought it was a real event and read the press releases over the airwaves at 1014 (CDT) and again at 1046 (CDT). At approximately 1400 (CDT) on the same day, the radio station told their listening audience of the mistake and stated STP was having a training exercise not a real event. The correction was broadcast over the airwaves three times every hour until midnight. This unplanned media event is being reported in accordance with 10CFR50.72(b)(2)(xi). This event is not significant with respect to the health and safety of the public. The licensee notified the NRC Resident Inspector. | |
| ENS 52142 | 1 August 2016 20:18:00 | 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release | Unintentional Release of Halon | At 1118 (CDT) during planned maintenance activities there was an unintentional release of approximately 146.5 pounds of Halon gas into an enclosed room in the Unit-2 Electrical Auxiliary Building. There was no impact to plant operations or plant personnel. The room was verified by station Safety Personnel to be safe for normal access. At 1518, Region 12 (Houston) of the Texas Commission of Environmental Quality (TCEQ) was notified of an event which met the requirements of 'Emission Event' for the TCEQ of a HALON release that exceeded the reportable quantity threshold of 100 pounds in a 24 hour period. No further actions are required by the TCEQ at this time and no press release is planned. The halon discharge was contained within the site protected area. Therefore, this event is not significant with respect to the health and safety of the public. The licensee has notified the NRC Resident Inspector. | |
| ENS 52303 | 18 October 2016 22:50:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty | A non-licensed supervisory employee had a confirmed positive for alcohol during a random fitness-for-duty test.. Unescorted access to the plant has been denied. The licensee notified the NRC Resident Inspector. | |
| ENS 52583 | 28 February 2017 16:30:00 | 10 CFR 26.719, FFD Reporting requirements | Fitness for Duty - Prohibited Item Found Inside Protected Area | Event Report per 10 CFR 26.719(b)(1). On February 28, 2017, a violation of the site Fitness For Duty policy was committed. A prohibited item was found inside the Protected Area. The licensee notified the NRC Resident Inspector. |