CPS Energy has used nuclear energy as a part of its diverse portfolio of fuel sources since the South Texas Project (STP) was completed in 1988. STP is located in Matagorda County, 90 miles west of Houston. Currently, nuclear energy comprises 36 percent of the fuel mix (second only to coal) used to provide electricity to over 680,000 CPS Energy customers. Nuclear energy keeps local utility bills low and reduces harmful carbon emissions.

How is Nuclear Energy Used To Make Electricity? 

Operators at STP Units 1 and 2 use pellets of uranium to heat water and create steam. The pellets are fixed into fuel assembly control rods inside the reactor. When the control rods are withdrawn, a reaction called fission begins. During fission, uranium atoms split as they absorb subatomic particles called neutrons. This process releases energy and additional neutrons, which then split other atoms.

The controlled reaction heats water circulating through sealed, stainless steel piping. The water is pressurized to 2,300 pounds per square inch (PSI) to keep the water in a liquid state at 600 degrees Fahrenheit. The sealed system, the primary loop, passes through huge vessels called steam generators. Inside the generators, the heat produced from the primary loop causes a separate system of cold water, pumped from cooling ponds, to boil. Much like a boiling pot of water on a stove, the hot water generates steam.

The wet steam is turned into dry steam and sent to a series of turbines outside a four-foot thick concrete containment wall fixed with hundreds of pounds of steel rods. The pressurized steam moves over the turbine blades causing it to spin. The steam passes through the series of turbines, which are connected to a generator by a long shaft. The mechanical motion powers the generator to create electricity.

After it turns the turbine blades, the steam is fed into a condenser and cooled by water from STP’s reservoir. The condensed water is then pumped back to the steam generators and the cycle starts again.