A Preliminary Study of the MSFR Dynamics

Abstract

In the last years, increasing interest has been focused on an innovative concept of Molten Salt Reactor (MSR) characterized by a fast neutron spectrum that combines the favorable characteristics of MSRs adopting molten salt fluorides both as fuel and coolant with those ones of fast neutron reactors. As a matter of fact, the Molten Salt Fast Reactor (MSFR) has been recognized as a long term alternative to solid-fuelled fast neutron systems and has been identified as reference Gen-IV configuration. Although considerable studies have been carried out for the analysis of the graphite-moderated MSR dynamics, the adoption of a fast spectrum configuration without graphite in the core is expected to notably modify the dynamic behavior of the system, thus requiring further investigation. In this paper, a preliminary analysis of the MSFR dynamics is performed allowing for the evaluation of the impact of some safety parameters (e.g., feedback coefficients and delayed neutron fraction) on the system behavior for different fuel cycle strategies. For this purpose, a simplified non-linear one-dimensional model of the primary circuit has been developed and the dynamic response of the system has been investigated with reference to different significant transient initiators, namely: unprotected transient overpower, unprotected loss of flow, and unprotected loss of heat sink. These analyses are thought to give a basic understanding of the MSFR dynamics, as well as significant indications in terms of the system safety parameters.