Controlling nuclear chain reactions

By Matthew Boulton, Joshua Cooper, George Gallagher, Jonathon Griffiths, Dharmveer Sharma

A diagram of a

chain reaction

When/where is control used?

• Nuclear power plants work by controlling the rate of the nuclear reactions, and that control is maintained through several safety measures. The materials in a nuclear reactor core and the uranium enrichment level make a nuclear explosion impossible, even if all safety measures failed.

• On the other hand, nuclear weapons are engineered to produce a reaction that is so fast and intense it cannot be controlled after it has started. When properly designed, this uncontrolled reaction can lead to an explosive energy release.

How the chain reaction is controlled• In a nuclear fission reaction in a nuclear

power plant, the radioactive element Uranium is used in a chain reaction.

The fission of splits off two neutrons, which in turn strike two atoms.

Two neutrons are split from each of the two atoms. Each of these neutrons then go on to strike another atom. Each of those atoms are split releasing two neutrons, which go on and hit more Uranium atoms.

The chain reaction continues on and on, getting bigger and bigger with each split.

The things that slow down a chain reaction are the control rods. A control rod is made up of cadmium or boron, which absorb neutrons. If you insert the control rod between the uranium atoms, the amount of neutrons available to cause more splits is reduced.

• THIS CAN BE DEMONSTRATED WHEN YOU PLACE A RULER IN BETWEEN FALLING DOMINOES