Define suction entrapment in a reactor coolant pump.

Define suction entrapment in a reactor coolant pump.

• A. Gas buildup in the suction line causing reduced flow
• B. Subcooling preventing gas locking
• C. Electrical faults in the motor
• D. Vapor condensation in the discharge line

Answer: (A)

Suction entrapment happens when gas bubbles build up on the suction side of a reactor coolant pump, creating a gas pocket that the impeller has to move instead of liquid. This reduces the amount of liquid entering the pump and lowers the effective suction head, so the pump can lose its smooth flow or even stall. In a reactor coolant system, dissolved gases or flashing due to pressure and temperature changes can generate these bubbles, leading to gas lock where the pump can no longer produce sufficient flow even though the discharge side may be pressurized. Gas buildup in the suction line is the defining feature because it directly changes the fluid entering the pump from liquid to a gas–liquid mixture, which undermines pumping performance. Subcooling helps prevent gas locking by keeping the liquid from flashing, but it isn’t the condition itself. Electrical faults in the motor pertain to drive equipment, not the suction flow, and vapor condensation in the discharge line occurs after the pump, not at the suction.

Suction entrapment happens when gas bubbles build up on the suction side of a reactor coolant pump, creating a gas pocket that the impeller has to move instead of liquid. This reduces the amount of liquid entering the pump and lowers the effective suction head, so the pump can lose its smooth flow or even stall. In a reactor coolant system, dissolved gases or flashing due to pressure and temperature changes can generate these bubbles, leading to gas lock where the pump can no longer produce sufficient flow even though the discharge side may be pressurized.

Gas buildup in the suction line is the defining feature because it directly changes the fluid entering the pump from liquid to a gas–liquid mixture, which undermines pumping performance. Subcooling helps prevent gas locking by keeping the liquid from flashing, but it isn’t the condition itself. Electrical faults in the motor pertain to drive equipment, not the suction flow, and vapor condensation in the discharge line occurs after the pump, not at the suction.