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| Entered date | Event description | |
|---|---|---|
| ENS 48467 | 31 October 2012 21:09:00 | During BFNP (Browns Ferry Nuclear Plant) NFPA (National Fire Protection Association) 805 transition review, it was determined in the event of an Appendix R fire, the ability to provide power to equipment needed to achieve and maintain safe shutdown may be adversely impacted. In certain fire zones/areas, feeder breakers for the 480V Shutdown Boards are credited for backup control operation using the 43 emergency switches, which isolate the breaker controls from circuits going to the control bay, and allow for local operation of the breaker. Fire damage to Main Control Room 480V Shutdown Board transfer switch cables could cause the control circuit fuses for the credited breaker to clear prior to the use of the 43 emergency switch. In addition, cable fire damage in the same fire areas could also cause the normal and/or alternate feeder breakers to spuriously trip. These breakers do not have separate emergency fuses like other BFNP breakers equipped with backup controls. Therefore, Safe Shutdown Instruction (SSI) procedure steps to use 43 switches to perform local breaker operation to supply power to safe shutdown equipment may not work as written where this cable fire damage can occur. Compensatory actions in the form of fire watches to mitigate this condition are in place in accordance with the BFNP Fire Protection Report. This condition is being reported pursuant to 10CFR50.72(b)(3)(ii)(B) and 10CFR50.72(b)(3)(v)(A),(B),(C).&(D). The NRC Resident Inspector has been notified. |
| ENS 48327 | 20 September 2012 20:47:00 | At 1240 CDT on 9/20/2012, Operations personnel determined that Browns Ferry Nuclear Plant had experienced a loss of assessment capability. The loss of assessment capability identified was due to not having functional seismic monitoring instrumentation during performance of a modification. The loss of seismic monitoring capability was determined to have existed from 8/17/2012 until 9/15/2012. The ability to declare an Unusual Event per Emergency Action Level 7.1-U or an Alert per Emergency Action Level 7.1-A could potentially be hampered by the unavailability of the seismic monitoring instrumentation, because the declarations would be based on personnel feeling an earthquake. In addition, the unavailability of the seismic monitoring instrumentation could potentially hamper the operators in determining the magnitude of an earthquake in order to determine if it reached Operating Basis Earthquake levels or Safe Shutdown Earthquake levels. Therefore, this event is being considered reportable as it results in a loss of emergency assessment capability. Compensatory measures were established on 9/15/2012 which restored assessment capability. This condition is reportable per 10CFR50.72(b)(3)(xiii). The NRC Resident Inspector has been notified. |