ABSTRACT
Real reactors are very complex and dynamic machines that very rarely, if ever, operate for more than a few seconds at exactly the same flux or power level. This is because the time-dependent neutron production and destruction rates are very rarely, if ever, precisely balanced, and so even a well-designed reactor will not be exactly critical all of the time. When both the time-dependent behavior and the spatial behavior are modeled at the same time, the study of this behavior is called space–time kinetics. This chapter focuses on the equations that are used to predict this behavior. George Robert Keepin found that different types of nuclear fuels produced delayed neutrons at different rates, and generally speaking, fuels that produced more delayed neutrons resulted in nuclear systems that were easier to control. Once created, both prompt and delayed neutrons take approximately the same amount of time to reach the thermal energy range.
