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| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 53392 | 8 May 2018 04:00:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition | On May 7, 2018 at 1041 CDT, Unit 1 performed an RCS (reactor coolant system) leakrate procedure that calculated an unidentified RCS leakrate of 0.202 gpm. The leak source investigation concluded at 2150 that the packing for the charging flow control valve (FCV) was the source of the RCS leakage when it was bypassed, which isolated the leakage. A second RCS leakrate calculation was performed after the charging flow control valve was isolated which calculated an acceptable leakrate of 0.00 gpm. The packing leakage from the charging flow control valve represented leakage external to containment which would result in a greater that 5 Rem dose projection to control room personnel during accident conditions which does not satisfy the GDC19 criteria described in Technical Specification Bases 3.7.10. Therefore the control room emergency filtration system would not be able to fulfill its design function resulting in an unanalyzed condition. This condition is being reported pursuant to 10CFR50.72(b)(3)(ii) for a 'condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety'. The packing leak from the charging flow control valve will remain isolated until repaired under work order SNC944374. The NRC Resident Inspector has been notified. | Reactor Coolant System Control Room Emergency Filtration System | |
| ENS 53159 | 9 January 2018 23:59:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Identified During National Fire Protection Association 805 Implementation | On January 9, 2018, at 1759 CST, during review of NFPA 805 requirements and circuit analysis, it was determined that the NFPA 805 analysis and Fire Safe Shutdown Modeling did not consider all fire-induced failures. As such, a condition could possibly exist during a postulated fire where both safety related electrical trains could be impacted. This notification is to report a condition involving the fire safe shutdown analysis. The condition could result in an adverse impact on the ability of operators to respond to a postulated fire in these areas. Therefore, this notification is being made pursuant to 10 CFR 50.72(b)(3)(ii)(B), any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety. Compensatory fire watches have been established in the affected areas. The licensee notified the NRC Resident Inspector.
Following additional refinements to the NFPA 805 Fire PRA Model, the circuits which initiated the initial report of an unanalyzed condition have now been evaluated and have proven that no significant degradation to plant safety existed. Therefore, EN 53159 is being retracted. The NRC Resident Inspector has been notified. Notified R2DO (Michel). | ||
| ENS 52414 | 7 December 2016 19:43:00 | 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Discovery of Non-Conforming Conditions During Tornado Hazards Analysis | During the evaluation of tornado missile vulnerabilities and the potential impacts to Technical Specification (TS) plant equipment, it was concluded that the following SSCs (systems, structures, and components) were vulnerable to tornado generated missiles. The Service Water Intake Structure (SWIS) intake and exhaust ventilation hoods, located on the roof of the SWIS, are not adequately protected from missiles generated by a tornado. Should a tornado-generated missile strike the SWIS intake and exhaust ventilation hoods, the hoods could crimp thus reducing air flow and challenging the performance of their heating and cooling safety functions. If the intake hoods were damaged or removed due to a missile strike, entry of rainwater could occur due to severe weather high wind velocity, and could affect safety related electrical equipment in the rooms directly below the hoods. These potential conditions could render Service Water trains inoperable on either or both units. This condition is reportable per 10 CFR 50.72(b)(3)(ii)(B) for any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety, and per 10 CFR 50.72(b)(3)(v)(D) for any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. This condition is being addressed in accordance with EGM-15-002 and DSS-ISG-2016-01 (enforcement discretion and interim guidance documents). Required actions have been taken. Corrective actions will be documented in a follow up licensee event report. The NRC Resident Inspector will be notified. The licensee is evaluating the operability of the service water system. Should one train be declared inoperable, the licensee would be in a 72 hr. LCO action statement. If both trains are inoperable, then the licensee would enter T.S. 3.0.3. | Service water | |
| ENS 49638 | 16 December 2013 22:27:00 | 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | Unanalyzed Condition Due to Unfused Direct Current Ammeter Circuits | At 1627 CST on December 16, 2013 Farley Nuclear Plant determined that the following was an unanalyzed condition: As a result of recent industry operating experience (OE 305419, EN 49411, EN 49419) regarding the impact of un-fused Direct Current (DC) ammeter circuits in the Control Room, Farley performed a review of ammeter circuitry for similar issues. The review determined the described condition to be applicable to Farley resulting in an unanalyzed condition with respect to 10 CFR 50 Appendix R analysis requirements. The wiring design for the ammeters contains a shunt in the current flow from each DC battery and battery charger, but the ammeter wiring attached to the shunt does not contain fuses. It is postulated that a fire could cause one of the ammeter wires to short to ground. Concurrently, the fire causes another DC wire from the opposite polarity on the same battery to also short to ground. This would cause a ground loop through the un-fused ammeter cable. The potential exists that the cable could heat up, causing a secondary fire in the ammeter raceway. The secondary fire could adversely affect safe shutdown equipment and potentially cause the loss of the ability to safely shutdown per 10 CFR 50 Appendix R. This condition is reportable in accordance with 10 CFR 50.72(b)(3)(ii)(B) as an unanalyzed condition. Compensatory measures have been implemented for affected areas of the plant. The NRC Resident Inspector has been notified. |