The licensee identified a finding of very-low safety significance (Green) and associated Non-Cited Violation of
Technical Specification 5.4.1.c which required that written procedures shall be established, implemented, and maintained covering the
Fire Protection Program implementation. Procedure MA-BY-EM-1-FP003-002, Diesel Generator and Day Tank Room Low Pressure
CO2 System Detection Test, was used by the licensee to test and calibrate the time delay relay that controls the time that
carbon dioxide is discharged in the 2A diesel generator room when the
carbon dioxide suppression system is actuated. The licensee's Fire Hazards Analysis for the 2A diesel generator room, Fire Zone 9.2-2, stated that the total flooding
carbon dioxide system would deliver a sufficient quantity of
carbon dioxide to maintain a 34 percent concentration for 10 minutes. Calculation
BYR 97-041 established that 70 seconds was required to achieve a 34 percent concentration of
carbon dioxide in the diesel generator room, and the preservice test for the
carbon dioxide system for that room established that a discharge time of 99 seconds was required to ensure a 34 percent concentration for 10 minutes. Contrary to the above, from January 30, 1987, when the Byron, Unit 2 operating license was issued, until October 19, 2015, when the procedure was revised, the licensee failed to maintain a procedure that verified the capability of the
carbon dioxide system. Specifically, Procedure MA-BY-EM-1-FP003-002 directed the maintenance technicians to verify the time delay relay was set between 60 and 80 seconds when the licensee's calculations required 70 seconds to achieve the required
carbon dioxide concentration in the room and 99 seconds to maintain that concentration for 10 minutes. The performance deficiency was determined to be more-than-minor because the issue adversely impacted the
Mitigating Systems Cornerstone objective to ensure the capability of systems that respond to
initiating events and prevent undesirable consequences due to external events such as fire. Specifically, the procedure allowed the
carbon dioxide system to be calibrated such that it might not have provided sufficient
carbon dioxide to extinguish a fire in the 2A diesel generator room. The inspectors screened the finding using
Inspection Manual Chapter 0609,
Significance Determination Process, Appendix F, Fire Protection
Significance Determination Process. Since the reactor was still able to reach and maintain a SSD condition, the finding screened as very-low safety significance (Green). The licensee entered the issue into the
CAP as
Issue Report 2571839, 2A Diesel Generator Room
CO2 Discharge Time, and revised the procedure to require a 100 second discharge time.
