First criticality

Global Nuclear Power Tracker entries may include "First criticality" dates as part of the project commissioning timeline. This field shows the date when the unit’s nuclear reactor is made critical for the first time. Criticality is the normal operating condition of a nuclear reactor. It is a state in which nuclear fuel sustains a fission chain reaction: each fission event in the nuclear fuel releases a sufficient number of neutrons to sustain an ongoing series of reactions.