Criticality accident

A criticality accident (also sometimes referred to as an "excursion" or "power excursion") occurs when a nuclear chain reaction is accidentally allowed to occur in fissile material, such as enriched uranium or plutonium. This releases neutron radiation which is highly dangerous to surrounding personnel and which causes induced radioactivity in the surroundings.

Related Topics:
Nuclear chain reaction - Fissile - Enriched uranium - Plutonium - Neutron radiation - Radioactivity

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When such incidents occur outside reactor cores and test facilities where fission is intended to occur, they pose a high risk both of injury or death to surrounding workers and of release of radioactive material. While dangerous, the low densities involved in these accidents limit the chain reaction, preventing them from becoming a nuclear explosion.

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