Subcritical mass

Definition

Subcritical mass is the amount of fissile material that is insufficient to sustain a nuclear chain reaction. It occurs when the neutron production rate is less than the neutron loss rate through absorption and leakage.

5 Must Know Facts For Your Next Test

1. A subcritical mass cannot sustain a chain reaction because it does not produce enough neutrons to continue fission.
2. When fissile material is below its critical mass, it will not lead to an explosive release of energy.
3. Neutron moderators and reflectors can affect whether a given amount of fissile material is subcritical or supercritical.
4. Subcritical masses are used in controlled settings such as nuclear reactors where chain reactions need to be carefully managed.
5. The concept of subcritical mass is crucial for understanding how nuclear weapons are designed to avoid premature detonation.

Related terms

Critical Mass:

The minimum amount of fissile material needed to maintain a self-sustaining nuclear chain reaction.

Supercritical Mass:

An amount of fissile material that exceeds the critical mass, leading to an increasing rate of fission reactions.

Neutron Moderator: A substance that slows down fast neutrons, making them more likely to cause further fission when they collide with fissile nuclei.