Engineering and administrative control of fissile material in fuel fabrication, storage, transport, reprocessing and laboratories so that k-effective stays safely below 1. The controlled parameters are mass, geometry, moderation, concentration, enrichment, reflection and neutron absorbers. Its central rule, the double contingency principle, means a process stays subcritical unless two separate, independent and unlikely upsets happen at the same time.
That's a favourable geometry tank, but if anyone swaps in a drum we lose the criticality safety basis.
Also heard as
- nuclear criticality safety
- NCS
Related terms
k-effective
The effective neutron multiplication factor: the ratio of neutrons in one generation to the previous one.
Criticality
The state in which a chain reaction sustains itself at a steady rate, with each fission causing on average exactly one more.
Poison
Any material that absorbs neutrons strongly, whether added deliberately for control or produced by fission.
Spent fuel pool
A deep, water-filled pool at a reactor where used fuel is stored to cool and to shield its radiation.