Although the construction of any new nuclear plant is at least a decade away, power plant owners are adding to their fleets through power uprates.
Utilities have been using power uprates since the 1970s as a way to increase the power output of nuclear plants. Uprate projects take advantage of digital technology, new materials and modern production techniques to increase output through equipment updates and enhancements.
Through dozens of uprates using efficiency gains, technological improvements and regulatory changes, power plants can increase their output from 2 percent to 20 percent based on a variety of factors.
To increase the power output of a reactor, typically more highly enriched uranium fuel and/or more fresh fuel is used. This enables the reactor to produce more thermal energy and therefore more steam, driving a turbine generator to produce electricity. To accomplish this, components such as pipes, valves, pumps, heat exchangers, electrical transformers and generators, must be able to accommodate the conditions that would exist at the higher power level.
For example, a higher power level usually involves higher steam and water flow through the systems used in converting the thermal power into electric power. These systems must be capable of accommodating the higher flows.
According to the NRC, there are three categories of power uprates:
- Measurement power uprates are less than 2 percent and are achieved by implementing enhanced techniques for calculating reactor power.
- Stretch power uprates are typically up to 7 percent and are within the design capacity of the plant and which do not involve major plant modifications.
- Extended power uprates are greater than stretch power uprates and have been approved for increases as high as 20 percent. These uprates require significant modifications to major balance-of-plant equipment.
The frequency and amount of uprates has varied from no added generation in a given year to as much as 1,000 megawatts in others.
At the forefront of this recent resurgence has been Exelon, the largest nuclear generator in the United States, with 17 generators with a capacity of nearly 17,000 megawatts. In the past decade, its uprate program has added the equivalent of 1,100 megawatts. Exelon is looking to add another 1,300 megawatts of capacity by 2017. Altogether, about 2,400 megawatts will have been added during the 18 years of the effort, the equivalent of two new plants.
In some instances, power plant owners will modify and/or replace components in order to accommodate a higher power level. Depending on the desired increase in power level and original equipment design, this can involve major and costly modifications to the plant such as the replacement of main turbines.
All of these factors must be analyzed as part of a request for a power uprate, which is accomplished by amending the plant's operating license. The Nuclear Regulatory Commission reviews and approves all applications for power uprates.
Projects like power uprates boost local economies, providing engineering and construction jobs locally, and continue to be the wave of the future for nuclear power owners.