Dynamics of passive reactor shutdown

Abstract

An analysis is presented of energy production during passive shutdown of an inherently safe reactor in case of loss of cooling without scram. After some time period autonomous recriticality occurs and system response is shown to be usually oscillatory with rather weak damping, due to the long thermal time constant of the passively cooled reactor. Relevant system parameters for the dynamical response are identified. It is demonstrated that kinetics of heat production by fission product decay can have a considerable influence on stability in this operational domain.