Critical mass

Definition

Critical mass is the minimum amount of fissile material needed to maintain a self-sustaining nuclear chain reaction. It is essential for the operation of nuclear reactors and atomic bombs.

5 Must Know Facts For Your Next Test

1. Critical mass depends on factors such as the shape, density, and purity of the fissile material.
2. Uranium-235 and Plutonium-239 are common materials that require critical mass considerations.
3. A supercritical mass occurs when there is more than enough material to sustain a chain reaction, leading to an exponential increase in reactions.
4. Subcritical mass means there is insufficient material to sustain a chain reaction.
5. Control mechanisms in nuclear reactors adjust the system to stay at or near critical mass to safely manage energy production.

Review Questions

• What factors influence the critical mass of a fissile material?
• Why is maintaining critical mass important in nuclear reactors?
• How do subcritical and supercritical masses differ in terms of nuclear reactions?

Related terms

Fission:

The process by which a nucleus splits into two or more smaller nuclei, along with the release of energy.

Chain Reaction:

A series of reactions where a reactive product or by-product causes additional reactions to take place.

Fissile Material: Materials capable of sustaining a chain reaction of nuclear fission. Examples include Uranium-235 and Plutonium-239.