Nuclear Power Plant Operations Quiz

High Energy Pipe Break Protection

• Two series isolation valves (7697A/B, 7698A/B, 7699A/B) are located inside the containment on each line from the steam generator to protect personnel and equipment outside the containment from a high energy pipe break of the blowdown system.
• These valves automatically close when high pressure (0.28-0.33 psig) is sensed in any room outside the containment where the blowdown piping is located.
• The valves will fail closed on a loss-of-power or loss-of-air.

Containment Isolation Valves (HV-7614A, B, and C)

• A containment isolation valve is located immediately outside the containment in each blowdown line.
• Each valve will automatically close upon an autostart of a motor-driven auxiliary feedwater (MDAFW) pump to aid in the recovery of the steam generator water level.
• These valves are controlled from the main control board (MCB) and fail closed on a loss-of-power or loss-of-air.

Steam Generator Blowdown Flow (FT-1171, 2, and 3)

• These instruments indicate the blowdown flow rate from each steam generator.
• Flow indication and low flow alarms are provided on the SGBD panel.
• The instruments, in conjunction with the associated flow controller (HIK-1171, 2, or 3), adjust the blowdown flow rate from each steam generator.

Steam Generator Blowdown Flow Control Valves (HCV-1171, 2, and 3)

• The air-operated blowdown flow control valves are modulated by their associated controllers (HIK-1171, 2, and 3) on the SGBD panel.
• The valves control the blowdown flow rate from each steam generator and fail closed on a loss-of-power or loss-of-air.

Steam Generator Shell Drain Pump

• The steam generator shell drain pump is used to lower the steam generator water level when it is cooled down < 200°F and depressurized.
• The pump has a 45 gpm capacity at 175' of head and receives power from motor control center MCC D.

Steam Generator Blowdown Heat Exchanger

• The heat exchanger sub-cools the blowdown fluid from steam generator exit conditions to 130°F, 10°F below the recommended maximum operating temperature for the demineralizer resin.
• The blowdown stream is cooled by service water to maintain a constant blowdown outlet temperature of approximately 130°F.

Steam Generator Blowdown Heat Exchanger Outlet Flow Control Valve (FCV-1152)

• This air-operated isolation valve automatically closes to protect the system or prevent the release of radioactive fluid to the environment.
• The valve will close on purification inlet filter high pressure, high heat exchanger outlet temperature, high activity, high surge tank level, and high flow.

Pressure Control Valve (PCV-1151)

• PCV-1151 maintains a constant pressure differential between the steam header pressure and the heat exchanger outlet.
• The backpressure on the hot blowdown fluid prevents excessive flashing upstream of the heat exchanger.
• The valve is controlled by pressure controller PC-1151 and fails closed on a loss-of-power or loss-of-air.

Steam Generator Blowdown Total Flow (FT-1152)

• FT-1152 indicates the total blowdown flow rate through the SGBD processing system.
• A high flow signal closes FCV-1152.

Steam Generator Blowdown Inlet Filter

• The inlet filter is designed to remove suspended particles in the blowdown stream to prevent plugging the resin beds.
• The filter is placed in service only during SGBD operation using the demineralizers.
• A bypass arrangement is provided for periods when demineralizer processing is not desired.

Demineralizer Bypass Valve (AOV-7604)

• When open, the air-operated demineralizer bypass valve will bypass the demineralizers.
• The valve is manually controlled from the SGBD panel and fails closed on a loss-of-power or loss-of-air.

Demineralizer Isolation Valve (TCV-1150)

• The air-operated demineralizer isolation control valve directs blowdown fluid to the demineralizers.
• The valve may only be open in the low range mode of operation and fails closed on a loss-of-power or loss-of-air.

Steam Generator Blowdown Demineralizers

• There are four demineralizers.
• The demineralizers are not presently used or maintained.

Steam Generator Blowdown Outlet Filter

• The outlet filter screens the demineralizer train effluent, eliminating the possibility of recycling or discharging resin particles.

Purification Outlet Radiation Monitor (RE-23A)

• The purification outlet radiation monitor determines the activity level of the fluid entering the surge tank.
• A high activity signal closes FCV-1152, which stops the blowdown.

Steam Generator Blowdown Surge Tank

• The surge tank provides a system surge capacity and ensures a sufficient net positive suction head (NPSH) to the discharge pumps.
• The surge tank has a capacity of 1420 gallons.
• A high level (90%) closes FCV-1152, while a low level signal (10%) shuts off the discharge pumps.

Steam Generator Blowdown Discharge Pumps

• Two canned motor pumps provide for recycle, discharge, and batch processing operations.
• Each pump has a design capacity of 75 gpm at a 350-ft head.
• The pumps are powered from 600V motor control center (MCC) C.

Steam Generator Blowdown Surge Tank Level Control Valve (LCV-1158)

• LCV-1158 is controlled from the surge tank level controller (LC-1158) located on the SGBD panel.
• The controller maintains 50% level in the tank by modulating LCV-1158.

Discharge Radiation Monitor (RE-23B)

• RE-23B monitors the activity level of the fluid leaving the SGBD.
• A high activity signal from this instrument closes RCV-23B, which prevents the discharge of high activity fluid to the environment.

Discharge Paths

• The blowdown fluid may either be discharged to the environment or to the main condenser.
• The normal path will be to the environment (river) via the service water dilution line.
• The blowdown will be recycled to the main condenser if the fluid does not meet the discharge limits or if a water conservation program is in effect.

Sample System Return

• The secondary sample system condensate return unit collects water from the steam system sample station and pumps the water collected to the SGBD system.
• When the SGBD system is shut down, the sample system condensate return unit continues to pump the water collected to the SGBD system.