"criticality accident: The release of energy as a result of accidentally producing a self-sustaining or divergent fission chain reaction. See reaction, fission.

criticality safety: Protection from the consequences of a criticality accident, preferably by prevention of the accident. Encompasses procedures, training, and other precautions in addition to physical protection. See criticality accident." NRC: https://www.nrc.gov/docs/ML0037/ML003731912.pdf