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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 56980 | 19 February 2024 15:45:00 | 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Loss of Reactor Building Ventilation | The following information was provided by the licensee via email: At 1045 EST, on 2/19/2024, during a maintenance activity, a loss of all reactor building ventilation occurred on Unit 2. With no flow past the ventilation radiation monitors, the radiation monitors were inoperable to support their ability to perform primary and secondary containment isolation functions or start the standby gas treatment system. Reactor building ventilation was restored within 15 minutes. Due to this inoperability, the radiation monitor system was in a condition that could have prevented fulfillment of a safety function; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector will be notified.
Upon further investigation, it was verified that the reactor building and the refueling floor radiation monitors are not needed to control the release of radiation for events described in chapter 14 of the updated Final Safety Analysis Report. For the analyzed loss of coolant accident (LOCA), the primary and secondary signals for this purpose were available and unaffected by this event. The radiation monitors provide a tertiary redundant method that is not credited within the station analysis. For all other analyzed accidents, the signal provided by the radiation monitors is not needed, as the secondary containment isolation function and start of the standby gas treatment system are not credited. Additionally, the fuel handling accident was not credible during the time of the event because no activities were in progress on the refueling floor. Therefore, the threshold for reporting the issue as an event or condition that could have prevented the fulfillment of a safety function was not met. The NRC Resident Inspector has been notified. Notified R1DO (Jackson) | Secondary containment Reactor Building Ventilation Standby Gas Treatment System | |
| ENS 45289 | 24 August 2009 18:15:00 | 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 | Station Safety Grade Pneumatic Supply Issue | This event is being reported pursuant to the requirements of 10 CFR 50.72(b)(3)(v) as an event or condition that at the time of discovery could have prevented the fulfillment of the safety function of systems supplied by the station safety-grade pneumatic supply. The systems affected include the primary containment isolation valves (i.e., large primary containment isolation valve boot seals) and the reactor-building to suppression pool vacuum breakers. On 8/24/09 at 1330, while troubleshooting the receipt of unexpected alarms during containment valve stroking the previous week, Exelon personnel discovered a valve closed instead of the expected open position. Licensed personnel concluded at 1415 that the out of position valve was restricting the Containment Atmospheric Dilution tank from supplying operating nitrogen to the Safety Grade Instrument Gas (SGIG) system headers for Peach Bottom Units 2 and 3. The valve was re-opened at 1445 (within the one hour action time required by Technical Specifications) and other system valves were verified to be in the required positions. The licensee notified the NRC Resident Inspector. | Primary containment | |
| ENS 42889 | 7 October 2006 21:50:00 | 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(ii)(A), Seriously Degraded 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | Technical Specification Required Shutdown Due to Loss of Primary Containment Integrity | At 17:50, on 10/07/2006, the Peach Bottom Atomic Power Station identified a crack approximately 4 inches long on a Unit 2, Reactor Core Isolation Cooling (RCIC) test line, as the line penetrates the Suppression Pool of Primary Containment. The degraded piping represents a loss of primary containment integrity, placing one of the principle safety barriers in a 'Seriously Degraded' condition as defined by 10CFR50.72 (b)(3)(ii)(A). This condition required a Reactor Shutdown per the plants Technical Specifications (TS) (TS 3.6.1.1). Unit 2 was manually scrammed, at 20:16, in order to shutdown the reactor and place the unit in Mode 3 per the Technical Specifications. The TS required shutdown is reportable per 10CFR50.72(b)(2)(i). The unplanned reactor scram is reportable per 10CFR50.72(b)(2)(iv)(B). The reactor scram and resultant Emergency Safety Feature actuations were completed as required. In addition, the loss of primary containment integrity represents a condition that 'could have prevented the fulfillment of a safety function of a structure required to control the release of radioactive material' and/or 'mitigate the consequences of an accident.' This is reportable per 10CFR50.72(b)(3)(v)(C) and (D). Unit 2 is currently shutdown, Mode 3, with an RPV cooldown in progress, with plans to Enter Mode 4 by 02:00 on 10/08/06. All control rods fully inserted on the Manual Reactor Scram. The reactor is currently being fed from the condensate system with decay heat being removed to the condenser via the MSL drains. The electric plant is in a normal shutdown lineup. See EN # 42887 for related NOTICE OF UNUSUAL EVENT. Additional 10 CFR Section not listed above: 50.72(b)(3)(v)(D) ACCIDENT MITIGATION The licensee notified the NRC Resident Inspector. | Reactor Core Isolation Cooling Primary containment Control Rod |