The tyranny of K equals 1

Considerations of nuclear safety generally conclude with the evaluation of keff. When k is < 1, the system is considered safe, and when k is <1, it is considered catastrophic. Kinetics evaluations are most often conducted without consideration of the mechanics and rate for the introduction of the additional reactivity. In reality, the energy release from a system in which reactivity is added slowly may be protracted over such a long period of time as to be inconsequential. In fact, if the rate of reactivity addition is sufficiently low, it is possible that k will never reach 1. Nevertheless, accident analyses that fail to include all aspects of kinetics are alarming and can lead to the requirement of additional analyses and costly, unnecessary mitigation features