The boron injection system ensures that negative reactivity control is available during each mode of facility operation. The components required include: (1) borated water sources, (2) charging pumps, (3) separate flow paths, (4) boric acid transfer pumps, and (5) offsite power or an emergency power supply from OPERABLE diesel generators.

With RCS average temperature ≥ 350°F, a minimum of two boron injection flow paths are required to ensure single functional capability in the event an assumed failure renders one flow path inoperable. The boration capability of either flow path is sufficient to provide a SHUTDOWN MARGIN from expected operating conditions of 1.3% delta k/k after xenon decay and cooldown to 200°F.

The maximum expected boration capability requirement occurs at EOL from full power equilibrium xenon conditions and requires borated water from a boric acid tank in accordance with TS Figure 3.1-2, and additional makeup from either: (1) the second boric acid tank and/or batching, or (2) a maximum of 41800 gallons of 2300 ppm borated water from the RWST. With the RWST as the only borated water source, a maximum of 73800 gallons of 2300 ppm borated water is required. The analysis assumes the most reactive control rod is not inserted into the core.

With RCS temperature below 350°F, one injection system is acceptable without single failure consideration on the basis of the stable reactivity condition of the reactor and the additional restrictions prohibiting CORE OPERATIONS and positive reactivity changes if the single injection system becomes inoperable.

The boric acid tanks, pumps, valves, and piping contain a boric acid solution concentration of between 3.75% and 4% by weight. To ensure the boric acid remains in solution, tank fluid temperature and process pipe wall temperatures are monitored to ensure a temperature of 63°F or above is maintained. A 5°F margin is provided to ensure the boron will not precipitate out. The tank fluid and pipe wall temperatures are monitored in the main control room.

Should ambient temperature decrease below 63°F, the boric acid tank heaters in conjunction with boric acid pump recirculation are capable of maintaining the boric acid at or above 63°F. A small amount of boric acid in the flowpath between the boric acid recirculation line and the suction line to the charging pump will precipitate out, but it will not cause flow blockage even with temperatures below 50°F.

The limits on contained water volume and boron concentration of the RWST also ensure a pH value of between 7.0 and 10.0 for the solution recirculated within containment after a LOCA. This pH band minimizes the evolution of iodine and minimizes the effect of chloride and caustic stress corrosion on mechanical systems and components.

The boron capability required below 200°F is sufficient to provide a SHUTDOWN MARGIN of 1% delta k/k after xenon decay and cooldown from 200°F to 140°F. This condition requires either 2600 gallons of 6560 ppm borated water from the boric acid storage tanks or 7100 gallons of 2300 ppm borated water from the RWST.

The 37000 gallon RWST limit for Modes 5 and 6 is based upon:

• 21210 gallons that is undetectable due to lower tap location
• 8550 gallons for instrument error
• 7100 gallons required for shutdown margin
• 140 gallons due to rounding up

The OPERABILITY of one boron injection system during REFUELING ensures that this system is available for reactivity control while in MODE 6.