Water is the unsung hero of our modern electrical grid. It is a critical part of most nuclear, coal, and gas plants where it carries the energy from fuel to spin the turbines that create electricity.
Over 95% of nuclear plants operating today use water for cooling. It has dictated where they can be built and represents the most significant way that nuclear energy impacts the local environment.
High-Temperature Gas-Cooled Reactors (HTGRs) flip the script: instead of using water, they can be used to protect water. With zero impact on marine ecosystems and the ability to develop resources locally without emissions in a wider variety of locations, they sit at the nexus of meeting energy demands and protecting the environment.
What Does Cooling Mean?
In thermoelectric power plants that rely on uranium, coal, or natural gas, fuel is used to create intense heat which is then carried by a coolant or working fluid to spin a turbine and generate electricity.
After this, either water or air is used to lower the temperature of the coolant and send it back to the heat source.
In a nuclear reactor, the coolant does not lower the heat of the fission reaction, but instead moves the heat away from the reactor core in a fluid material that can both absorb this heat and spin the turbine.
Coolant is a critical component of the system. Not only is it essential for creating electricity, but if the heat stays trapped, the reactor core can overheat.
The Classic Water-Cooled Designs
Almost all nuclear reactors operating today use water with a very specific chemical composition as the coolant. Pressurized water reactors and boiling water reactors handle water differently to generate power, but fundamentally use heat from the fission reaction to boil water and spin a steam turbine.
Crucially, this very specific water is cycled in a closed loop past the core and represents a very small fraction of nuclear power’s water needs.
Where these plants use significant volumes of water is in a separate condenser system that cools the steam coming from the reactor. Most plants use a once-through system, pulling between 25,000 and 60,000 gallons of water per megawatt-hour from adjacent lakes or oceans and returning over 99 percent of it slightly warmer. It does not get near the radioactive core.
There are also closed-loop systems for cooling nuclear plants with water in more arid locations. These slash water consumption to between 800 and 2,600 gallons per megawatt-hour, but lose a significant portion to evaporation instead of returning it to local sources.
Environmental Impacts of Water-Cooled Reactors
Drawing massive volumes of water can have significant impacts on the local environment. Fish and other aquatic organisms sometimes get trapped on intake screens or swept into the cooling system.
Returning this water to the environment also creates thermal pollution, as warmer discharge can disrupt marine life. Warmer water holds less oxygen which can stress fish and aquatic plants. It can also accelerate harmful algal blooms.
To protect local ecosystems, modern plants use treatment systems to clean any water before discharge and ensure radiological emissions remain well below strict safety limits. This careful management ensures that water remains safe for neighboring communities and animals.
Trading Water for Gas
High-Temperature Gas Reactors such as StarCore’s design replace water with gas. These reactors use chemically inert helium as their primary coolant because it can withstand extreme heat without boiling or reacting with core materials.
Using a gas coolant maximizes the efficiency of producing power by allowing for more of the heat from the reactor to be converted into useful energy.
In a water-cooled reactor, a lot of energy is lost in the steam cycle, which is why it can increase the temperature of local water sources.
Gas-cooled reactors are much better at absorbing heat from the reactor and transferring it to the turbines to generate electricity. They are cooled by air instead of water, and the excess heat can be repurposed to meet community needs, all without tapping into local bodies of water.
Creating Solutions for Remote Communities
The very hot air coming out of the turbine can be used to power water purification facilities or manufacture zero-emission hydrogen fuel, improving local resource security.
The lower temperature heat from the ambient air cooling system is perfect for indoor agriculture or district heating, reducing the need to import food and fuel.
Water is essential, but we don’t need it to produce electricity. HTGRs turn nuclear power from a water consumer into a vital partner for environmental protection and open the door for clean and reliable energy in arid climates, isolated mining sites, or remote communities.
