What is the role of deuterium oxide in heavy water reactors?

Deuterium oxide, commonly known as heavy water, plays a crucial role in heavy water reactors primarily as both a coolant and a moderator. Its unique properties allow it to efficiently slow down neutrons without capturing them, which is essential for sustaining the nuclear fission chain reaction.

As a moderator, heavy water facilitates the interaction of neutrons with the fissile material (like uranium-235 or plutonium-239) by slowing down the fast neutrons produced during fission, increasing the likelihood of further fission events. This is important because slower (thermal) neutrons are much more effective for inducing fission in certain materials used in these reactors.

As a coolant, deuterium oxide carries heat away from the reactor core following the fission process. The ability to absorb and transport heat while remaining in a liquid state is essential for maintaining the reactor's operational safety and efficiency.

This dual role allows heavy water reactors to operate effectively, often using natural uranium as fuel, which distinguishes them from light water reactors that require enriched uranium. The properties of heavy water make it highly beneficial in maintaining the reactor's functionality and safety.