Semantic search
| Entered date | Event description | |
|---|---|---|
| ENS 46712 | 30 March 2011 17:00:00 | An extent of condition review of Braidwood Unit 2 unplanned loss of safety system annunciators Emergency Plan Unusual Event on March 24, 2011 (ENS number 46694) was performed for both Units of Braidwood Station. During this review it was identified that a previous unknown loss of annunciators had also occurred on August 10, 2010 from 1024 to 1136 CT on Unit 2. This condition occurred during planned maintenance on annunciator cabinet 2PA19J power supply capacitors. The maintenance performed on August 10, 2010 would normally not cause a loss of all Unit 2 annunciators. During the work, it was expected to lose approximately one third of the annunciators. Latent annunciator system problems identified from the March 24, 2011 event caused a loss of all Unit 2 annunciators and contributed to this condition being unknown to Main Control Room operators. All Unit 2 indications and computer points to the sequence of events recorder remained available and Unit 2 was stable during this timeframe. At 1538 CT on 3/30/11, it was determined that the August 10, 2010 condition met the threshold for Emergency Action Level MU6, UNPLANNED loss of most or all safety system annunciation or indication in the control room for greater than 15 minutes. This notification is being made as an undeclared Unusual Event Emergency Plan Classification per 10 CFR 50.72(a)(1)(ii). Per NUREG 1022, a 1- hour notification is required when a condition existed which met the emergency plan criteria but no emergency was declared and the basis for the emergency class no longer exists at the time of the discovery. The licensee notified the NRC Resident Inspector. |
| ENS 46415 | 12 November 2010 15:44:00 | At 1300, on November 12, 2010, Exelon Generation Company LLC concluded that inaccurate information contained in the PRA technical bases for a 1987 License Amendment Request (LAR) for Byron and Braidwood Stations would have potentially impacted the acceptability of the LAR by the NRC. The LAR was to extend Allowed Outage Times (AOT) from 72 hours to 7 days for several systems, to include the Component Cooling (CC) and Residual Heat Removal (RH) Systems. The original design intent of the CC system was that each unit has two independent CC pumps and a fifth pump (U0) CC pump could be used as an operable spare for any of the unit specific pumps. This is how CC was modeled in the PRA technical justification for the 1987 LAR. However, a piping configuration design flaw that was recently evaluated in that the U0 CC pump could not be considered an operable spare for either unit's B pumps was not correctly modeled in the PRA. During the evaluation to assess the potential significance of this CC design flaw on the PRA justification for the 1987 LAR, another potentially significant discrepancy was discovered in that it appears the operational practice to always split CC trains after a design basis LOCA was not modeled correctly in the RH analysis. Administrative controls have been put in place to restrict the AOT for the CC pumps and RH trains to the pre-LAR timeframe of 72 hours pending the permanent corrective actions. In addition, administrative controls have been put in place to prohibit the U0 CC pump from being an operable spare for either unit's B trains. This event is being reported as an unanalyzed condition that significantly degrades plant safety under 10 CFR 50.72(b)(3)(ii). The NRC Resident Inspectors have been notified |
| ENS 46414 | 12 November 2010 15:44:00 | At 0818 CST, 11/12/10, Radiation Protection determined that the setpoints for the Control Room Outside Air Intake Noble Gas channels are non-conservative. This affects Tech Spec 3.3.7 required monitors 0PR31B, 0PR32B, 0PR33B and 0PR34B (Noble gas channels). The current setpoints for 0PR31B, 0PR32B, 0PR33B and 0PR34B are High Alarm 9.55E-05 microCi/cc and Alert Alarm 9.55E-06 microCi/ml. The calculated required setpoints are High Alarm 6.61E-05 microCi/cc and Alert Alarm 6.61E-06 microCi/cc. This is approximately a 30% decrease in setpoints from the current setpoints. LCO 3.3.7 conditions A and B were entered at 0818, 11/12/10. LCO 3.3.7 conditions A and B required actions completion time is 1 hour. All required actions were complete at 0900 11/12/10, less than 1 hour. This report is being made per 10 CFR 50.72(b)(3)(v), Event or condition that could have prevented fulfillment of a safety function, 8 hour non-emergency notification. Both trains of radiation monitor setpoints were non-conservative and actuate control room ventilation in emergency mode. The margin available in the control room dose analysis will be reviewed to confirm impact on safety function. The setpoints have been non-conservative since 1999. The licensee notified the NRC Resident Inspector.
At 0818 CST, 11/12/2010, Radiation Protection determined that the setpoints for the Control Room Outside Air Intake Noble Gas channels are non-conservative. This affects Tech Spec 3.3.7 required monitors 0PR31B, 0PR32B, 0PR33B, 0PR34B (Noble Gas channels). ENS notification was made under ENS 46414 under 10 CFR 50.72(b)(3)(v)(D). The design basis accidents do not credit automatic actuation of the Control Room Outside Air Intake system to the Emergency mode from a high radiation signal. Therefore, the high radiation signal is not needed to mitigate the consequences of an accident and this event did not result in a safety system functional failure. Therefore, ENS notification 46414 is being retracted. The licensee notified the NRC resident inspector. Notified R3DO (Bloomer) |
| ENS 45618 | 9 January 2010 21:33:00 | At 1925 (hrs. CST), the Main Control Room received a notification of smoke in the Auxiliary Building Ventilation Supply Plenum. Fire Brigade and the Incident Commander were dispatched. Once (they) arrived at the scene, they noted smoke in the area of the 0C VA Supply Fan and requested the fan be shutdown. The 0C VA supply fan was shutdown at 1933 hrs. The operators reported smoke and a small fire coming from the inboard bearing of the 0C VA supply fan. A CO2 fire extinguisher was used to put the fire out and cool the bearing. A total of 2 extinguishers were used. The fire was declared out at 1941 hrs. Both Units remained stable and at full power during the entire event. There were no injuries, and no off site assistance was required. The licensee notified state and local authorities and the NRC Resident Inspector.
At 2111 CST (on) 1-9-2010, the Unusual Event was terminated. The fire is out. Both Units are stable. A fire watch is established. There are no signs of reflash. (Braidwood) no longer (meets the) Unusual Event action level threshold. The licensee has notified the NRC Resident Inspector. Notified IRD (Grant), R3DO (Stone), NRR EO (Giiter), DHS (Inzler) and FEMA (Casto). |
| ENS 45017 | 24 April 2009 15:15:00 | At 1141 CT, Braidwood Unit 2 experienced an automatic Reactor Trip. The Reactor Trip red first out annunciator was Over Temperature Delta Temperature (OTDT). At the time of the Reactor Trip the Instrument Maintenance Department was performing a scheduled calibration of a Pressurizer Pressure channel (2PT-456) which is in the B loop of reactor protection. During the calibration a spike occurred on the D loop of reactor protection. Specifically, the RCS (Reactor Coolant System) temperature for the D loop. This caused a Reactor Trip on a 2 of 4 coincidence. After the reactor trip occurred, all four steam generators reached their low-2 Reactor Trip setpoints and pressurizer pressure reached its low pressure Reactor Trip setpoint all of which is an expected response on a trip from full power. Steam Generator levels and Pressurizer pressure have been restored. Both the 2A and 2B Auxiliary Feedwater pumps auto started on the low-2 steam generator levels as expected. All control rods fully inserted into the core. No secondary relief valves lifted and no secondary steam released as a result of the Reactor Trip. Steam Generators are now being filled by the 2A Main Feedwater pump and the Auxiliary Feedwater pumps have been placed in standby. The main steam dumps are in service to the main condenser to provide heat sink cooling. The plant is being maintained at normal operating pressure and temperature. This report is being made per 10 CFR 50.72(b)(2)(iv)(B) for RPS actuation, 4 hour notification, and per 10 CFR 50.72(b)(3)(iv)(A) for automatic actuation of the Auxiliary Feedwater System, 8 hour notification. The electrical line up transferred to the normal shutdown configuration with the standby diesel generators and safety systems available. There is no Unit 1 impact. The licensee plans on issuing a press release and has notified the NRC Resident Inspector. |
| ENS 44743 | 27 December 2008 18:36:00 | At 1418 on 12-27-08 Braidwood Unit 2 experienced an automatic Reactor Trip. The Reactor Trip red first out annunciator was Turb(ine) Trip above P8 Rx Trip. At the time of the trip the Unit Aux Transformer (UAT) 241-1 sudden pressure relay actuated causing a main generator trip which resulted in a main turbine trip which resulted in a Reactor Trip. Also at the same time as the Reactor Trip, the 2C Heater Drain Pump tripped on phase A over current. Damage was subsequently noted on the pump motor terminal box. No fire or smoke was observed at UAT 241-1 or the 2C Heater Drain Pump. After the Reactor Trip occurred, all four steam generators reached their low-2 Reactor Trip setpoints and the pressurizer reached its low pressure Reactor Trip setpoint all of which is an expected response on a trip from full power. Steam generator levels and pressurizer pressure have been restored. Both the 2A and the 2B Auxiliary Feedwater Pumps auto started on the low-2 steam generator levels as expected. All control rods fully inserted into the core. No secondary relief valves lifted and no secondary steam was released as a result of the Reactor Trip. Steam generators are now being filled by the Startup Feedwater Pump and the Auxiliary Feedwater Pumps have been placed in standby. The main steam dumps are in service to the main condenser to provide heat sink cooling. The plant is being maintained at normal operating pressure and temperature. This report is being made per 10CFR 50.72(b)(2)(iv)(B) for RPS actuation, 4 hr (notification), and per 10CFR 50.72(b)(3)(iv)(A) for automatic actuation of the Auxiliary Feedwater System, 8 hr (notification). The electrical line up transferred to the normal shutdown configuration with standby diesel generators and safety systems available. There was no impact on Unit 1. The licensee plans on issuing a press release and has notified the NRC Resident Inspector. |
| ENS 43137 | 1 February 2007 12:18:00 | At approximately 0925 CST, Braidwood lost approximately 85% of phone functionality. The loss of phones has been determined to be an off site issue and the local phone company is investigating the situation. The Emergency Response Organization (ERO) can still activate ERO pagers using cell phones. The Shift Manager has a dedicated cell phone. The licensee notified the NRC Resident Inspector.
The licensee declared the ENS and commercial lines operable based on testing and information from the telephone company. The R3DO (Hills) has been notified. |
| ENS 42187 | 3 December 2005 12:25:00 | This notification is being made pursuant to Braidwood Station Unit 1, Operating License Condition 2.G, which requires a 24 hour notification to the NRC Operations Center for reactor power operation in excess of 3586.6 megawatts thermal (100 percent rated power), i.e., a violation of Operating License Condition 2.C (1)- Braidwood Station will, following this notification, provide a written report within thirty days in accordance with the procedures described in 10 CFR 50.73(b), (c), and (e). Braidwood Station, Unit 1 experienced a Feedwater temperature transient on November 18, 2004, which caused reactor power to momentarily increase and peak at approximately 101.2% as indicated on the excore nuclear instrumentation system. The duration that reactor power remained above 100% was approximately one minute. Subsequent to the event, a number of peer reviews were conducted to validate that power did not exceed 102%. The results of these reviews questioned the methodology used to determine the power level at the time of the transient. Industry was consulted regarding methodologies appropriate for power level measurement during transient conditions. At 1700 on December 2, 2005, an independent Exelon task force concluded, using a conservative methodology, that reactor power level during this transient did exceed 100% for approximately one minute and was limited to a peak of approximately 103.5% and that the appropriate reports, as specified in the Operating License, should be initiated. This overpower transient, caused by the loss of a Feedwater heater string, is bounded by the Feedwater design basis transient described and analyzed in UFSAR, Section 15.1.1, "Feedwater System Malfunctions Causing a Reduction in Feedwater Temperature, therefore, the event did not place Braidwood Unit 1 in an unanalyzed condition that significantly degraded plant safety. No safety limits were exceeded and there was no impact on the health and safety of the public. The licensee has notified the Resident Inspector. The licensee notified the NRC Resident Inspector. |
| ENS 42184 | 2 December 2005 11:45:00 | This notification is being made pursuant to 10 CFR 50.72(b)(2)(xi) for a press release issued by Exelon Nuclear at 10:00 AM CST on December 2, 2005 regarding elevated levels of tritium found in groundwater on the Braidwood Station site property near the plant's north boundary. An environmental monitoring program at the Braidwood Generating Station has found higher than normal concentrations of tritium close to an underground pipe inside the plant's northern boundary, and the station has begun a remediation program. An Exelon Nuclear environmental team is drilling test wells on and just beyond the Braidwood property line in order to determine how much tritium may have moved beyond the plant boundaries and ultimately to clean up the tritium. Exelon Nuclear has notified NRC regional personnel, appropriate state agencies, local and state elected officials and four property owners who are potentially affected. The tritium was found in shallow groundwater 8 to 15 feet deep on company property. It poses no health or safety risk to the public and does not threaten drinking water wells in the area. Tritium is a naturally occurring isotope of hydrogen that emits a very low level of radiation and is a natural part of water. It is found in more concentrated levels in water used in nuclear reactors. The closest private residential wells to the site showed no tritium above natural background levels. A sample of water from a pond 50 yards north of the plant property line showed tritium levels of about 2,400 picocuries per liter, above background levels but less than one-eighth of the federal drinking water limit. The residential and pond test samples were taken with the consent of property owners and the results received on Dec. 1. The underground pipe that passes near the monitored site in the past has carried water containing tritium from the plant to the Kankakee River, where it was periodically discharged under federal guidelines as part of normal plant operations. No tritiated water is currently in the pipe and no tritium is currently being introduced into the ground. Braidwood has not released levels of tritium that exceeded federal limits. The licensee notified the NRC Resident Inspector, State and local agencies and has issued a press release. |