How the First Nuclear Reactor Works

The foundational 1955 patent by Enrico Fermi and Leo Szilard describing the design of the first nuclear reactor capable of a self-sustaining chain reaction.

What it covers

The patent defines the critical physical requirements for a nuclear reactor to achieve a self-sustaining chain reaction. It specifies a lattice structure where natural uranium rods are embedded in a graphite moderator. The claim explicitly links the geometry, the volume ratio of the graphite to the uranium, and the material purity to the 'k=1.00' curve, which represents the threshold where the number of neutrons produced equals the number of neutrons lost. By maintaining these precise parameters, the system ensures that the fission process continues without external intervention.

What it doesn't cover

• —Does not cover reactors using enriched uranium fuel, as the claim specifies natural uranium.
• —Does not cover non-graphite moderation systems, such as heavy water or light water reactors.
• —Does not cover specific control rod mechanisms or safety shutdown systems.

The clever bit

The inventors realized that the geometric arrangement and the purity of the materials were just as critical as the fuel itself to prevent neutrons from being absorbed by impurities before they could cause further fission.

Why it matters

This is the seminal patent for nuclear power. It codified the physics discovered during the Manhattan Project into a technical blueprint, effectively launching the nuclear age. It remains a primary reference in the history of energy production and nuclear engineering.

Real-world examples

• 1.Chicago Pile-1
• 2.Graphite-moderated nuclear reactors
• 3.Early plutonium production reactors