Part 1 of 2 Parts
Current commercial nuclear power plants are massive, technically complicated, difficult for the public to understand. Recently there has been a lot of media about “advanced nuclear reactors”. Advanced nuclear is an ill-defined category that basically includes anything different from the commercial reactors operating now. Those all follow the same general formula. The subject of this post is an overview of advanced nuclear reactors.
We begin our overview with a recap of the basics of nuclear power generation. Commercial nuclear power plants generate electricity via fission reactions, where atoms split apart, releasing energy as heat and radiation. Many neutrons are released during these splits, and they collide with other atoms and split them, creating a chain reaction.
In nuclear power plants today, there are basically two absolutely critical pieces. The first critical part is the fuel, which is consumed to feeds the reactions. It is vital that the chain reactions happen in a controlled manner, or the system may suffer a nuclear meltdown. The second critical part of a nuclear plant is the cooling system, which keeps the whole reactor from overheating and causing problems. (There’s also the moderator and many other parts which will not be a part of our overview.)
In the vast majority of nuclear power reactors on the electrical grid today, these two components follow the same general formula. The fuel is enriched uranium that’s packed into ceramic pellets, loaded into metal tubes, bundled into fuel assemblies and inserted into the reactor’s core. The cooling system pumps pressurized water around and through the core of the reactor to keep the temperature within operation bounds.
But for a whole host of reasons, companies are beginning to work on making important changes to this tried-and-true formula. There are about seventy companies in the U.S. working on designs for advanced nuclear reactors. Six or seven are far enough along to be working with regulators, says Jessica Lovering. She is the cofounder and co-executive director of the Good Energy Collective which is a policy research organization that advocates for the use of nuclear energy.
Many of these so-called advanced reactor technologies were invented and even demonstrated over 50 years ago. This happened before the nuclear industry converged on the standard water-cooled nuclear plant designs. However, now there’s renewed interest in getting alternative nuclear reactors up and running. New reactor designs could help improve safety, efficiency, and cost.
Alternative coolants could improve on safety over water-based designs because they don’t always need to be kept at high pressures. Many coolants can also reach temperatures higher than current nuclear plant operating temperatures, which can allow reactors to run more efficiently.
Molten salt is one leading contender for alternative coolants. It is used in designs from Kairos Power, Terrestrial Energy, and Moltex Energy. These designs can produce the same amount of power while using less fuel than conventional reactors. And they produce nuclear waste that is easier to manage.
Other companies are looking at liquid metals, including sodium and lead, as coolants. There are a few sodium-cooled reactors operating today, mainly in Russia. That country is one of the pioneers in developing lead-cooled reactors. Reactors cooled by liquid metals share many of the potential safety benefits of molten-salt designs. Helium and other gases can also be used as a coolant for nuclear power reactors that require higher temperatures than water-cooled systems. X-energy is designing a high-temperature gas-cooled reactor that utilizes helium as a coolant.
Please read Part 2 next