Waste Heat Treatment Facility

Cooling Lagoons

North Anna Power Station uses water from Lake Anna to condense steam back to water inside the station. The water is returned to the lake slightly warmer than when it was taken. The discharged water cools in a series of private cooling lagoons, known as the Waste Heat Treatment Facility (WHTF). When North Anna is in full operation, approximately 2,000,000 gallons of water pass through the station per minute.

Reservoir and WHTF Background

Lake Anna was developed to provide cooling water for North Anna.

It was originally timberland and some farmland. When construction of North Anna began, the area that would become the lake bottom was completely cleared in 1968 before filling with water.

In 1972, the North Anna River was impounded, forming Lake Anna and the adjacent Waste Heat Treatment Facility.

Lake Anna is 17 miles long, 1 1/2 miles wide, and offers 200 miles of shoreline. There are 9,600 acres in Lake Anna and 3,400 acres in the private WHTF. In 1972, the Commonwealth of Virginia stocked the lake with 5 1/2 million fish, and it is restocked periodically. Some 33 species of fish thrive in the lake, including largemouth bass, striped bass and catfish.

Lake Anna Conditions

Lake Anna's water level and temperature readings are updated once each weekday. The temperature is measured in water being drawn directly from the main lake into the station's intake. The lake level is based on feet above sea level as measured at the main dam.

Discharge Water Temperature

By design, the temperature of the discharge water is typically 14 degrees warmer than the intake water. Intake temperatures can fluctuate with seasons or weather conditions. View the current temperature of the discharge water below as it initially leaves the station. The data is updated approximately every 15 minutes. ("Refresh" your browser for the latest reading.)

Cooling System

The process of generating electricity at North Anna begins with the fission, or splitting, of uranium atoms in the reactor vessel. The vessel is filled with water (not from the lake), which controls, or moderates, the fission process, and removes heat from the reactor core. This water is kept under very high pressure, which prevents it from boiling although it is heated to three times the normal boiling temperature.

This hot, pressurized water is pumped to nearby steel containers called steam generators. In the steam generators, the water passes through thousands of small U-shaped tubes — about the diameter of your little finger — transferring its heat to a second, slightly cooler water system. This secondary water becomes steam, which travels through large pipes to spin the turbines in the adjoining building.

Spinning at 1,800 RPM, the turbines drive a generator that produces electricity. The steam then is condensed back to a liquid by a third cooling system before it returns to the steam generator to start the process again. The third cooling system's water comes from Lake Anna, and flows through the private WHTF before returning to the lake.

» View an animation of the cooling process.