What Is Nuclear Criticality? How Much Clean Energy Can It Produce?

Albert Einstein had foreseen that nuclear energy would secure the energy needs of the world, or that it could be quite dangerous. In 1939, Einstein and other scientists wrote a famous letter to Franklin D. Roosevelt explaining that a nuclear chain reaction in uranium could release vast amounts of power and might soon become possible.

We have now moved on from the gloomy days of the Manhattan Project. Today, nuclear reactors generate about 10% of the world’s electricity, mostly using fuel like Uranium-235. Highly advanced technologies such as Fast Breeder Reactor could potentially expand this share in the future possibly to 25 - 30% by creating more consumable fuel while producing power, allowing nuclear energy to supply a larger portion of clean electricity globally.

How is nuclear energy produced?

Nuclear energy is produced through Nuclear Fission. In this process, atoms of fuel such as Uranium‑235 split when struck by neutrons, releasing a large amount of heat and more neutrons. It is like a domino effect on a large basis at a microscopic scale. The heat released is used to boil water into steam, which spins turbines connected to generators to produce electricity—similar to how thermal power plants work, but the heat source is nuclear rather than coal or gas.

What is Nuclear Criticality?

Nuclear criticality is the point at which a nuclear chain reaction becomes self-sustaining. In a reactor, atoms of fuel (usually uranium or plutonium) split during fission and release neutrons. When each fission event causes exactly one more fission on average, the reaction stays stable and continues producing energy steadily. This balanced state is called criticality, and it is carefully controlled inside nuclear reactors using control rods and moderators.

Why is it difficult?

Achieving Nuclear Criticality is difficult because it requires quite an advanced technology to produce and handle fissile fuels like Uranium-235 or Plutonium-239, along with extremely precise reactor engineering to control the Nuclear Chain Reaction safely. It demands huge investments, large Uranium or Thorium reserves, and decades of scientific expertise. 

What is a breeder reactor?

A breeder nuclear reactor is designed to create more usable nuclear fuel than it burns. It converts abundant but non-fissile materials like Uranium‑238 or Thorium‑232 into fissile fuels such as Plutonium‑239. Because of this fuel-breeding capability, breeder reactors can dramatically extend nuclear fuel resources and are considered important for long-term nuclear energy strategies. In principle: a breeder reactor can produce more fissile fuel than it consumes.

What could be the future share of nuclear energy?

Many energy projections suggest that nuclear could rise to 25 - 30% of global electricity if countries expand reactors and adopt advanced designs like breeder reactors and small modular reactors. Nuclear energy is attractive because it produces large amounts of power with very low carbon emissions. It can support large-scale electricity, thorium energy, hydrogen production, industrial heat, desalination, and low-carbon power systems.