Capacity uprate
A licensed increase in the maximum power output of an existing power plant, most commonly a nuclear reactor, achieved through better measurement or equipment upgrades.
A capacity uprate raises the licensed thermal power of a reactor, and with it electrical output, without building a new unit. The US Nuclear Regulatory Commission distinguishes three types:
- Measurement uncertainty recapture: up to about 1.5–2%, enabled by more accurate feedwater flow meters that reduce the required safety margin.
- Stretch uprates: typically up to 7%, using existing design margins with minor hardware changes.
- Extended power uprates: up to 20%, requiring major upgrades to high-pressure turbines, condensate pumps, generators, transformers and feedwater heaters.
Since 1977 the NRC has approved more than 170 uprates adding about 8 GWe, equivalent to around eight large reactors. Uprates are among the cheapest sources of new firm low-carbon capacity, often USD 1,000–4,000/kW against USD 8,000–12,000/kW or more for new large reactors in the West. Renewed interest from data-centre demand after 2024 led US utilities to announce further uprate programmes of several GW, alongside licence extensions to 80 years.
Uprates also apply to hydro (turbine runner replacement), wind (repowering) and gas turbines (upgraded hot-gas-path parts). See PWR and BWR.
Related terms
All terms →- Pressurised water reactor (PWR)
The most common nuclear reactor type, in which water under high pressure cools the core without boiling and transfers heat to a separate steam circuit.
- Boiling water reactor (BWR)
A light-water nuclear reactor in which coolant boils in the core and the resulting steam drives the turbine directly, without steam generators.
- Repowering
Replacing ageing generating equipment at an existing site with newer, usually larger and more efficient technology, most commonly applied to wind farms after 15 to 25 years.
- Capacity factor
The ratio of the energy a power plant actually produces over a period to the energy it would produce running at full nameplate capacity for the whole period.
- Nuclear fission
The splitting of a heavy atomic nucleus such as uranium-235 or plutonium-239 into lighter nuclei after absorbing a neutron, releasing about 200 MeV of energy and further neutrons.