What is k eff?

Keff (effective multiplication factor) is a measure of the efficiency of a nuclear reactor in producing more fission reactions than the number of neutrons lost from the core.

The k eff value indicates whether the reactor is critical, subcritical, or supercritical. A k eff of 1 indicates a critical state, where the reactor is producing the same number of neutrons as it loses. A k eff greater than 1 indicates a supercritical state, where the reactor is producing more neutrons than it loses, leading to a potential increase in power output. A k eff less than 1 indicates a subcritical state, where the reactor is losing more neutrons than it produces, leading to a decrease in power output.

Keff is influenced by a variety of factors including the reactor design, fuel composition, and reactor operating conditions. Reactor operators use k eff to monitor and control reactor output and to ensure safe and efficient operation.