Safety assessment of molten salt reactors in comparison with light water reactors

Molten salt reactors (MSRs) have a long history with the first design studies beginning in the 1950s at the Oak Ridge National Laboratory (ORNL). Traditionally these reactors are thought of as thermal breeder reactors running on the thorium to 233U cycle and the historical competitor to fast breeder reactors. In the recent years, there has been a growing interest in molten salt reactors, which have been considered in the framework of the Generation IV International Forum, because of their several potentialities and favorable features when compared with conventional solid-fueled reactors. MSRs meet many of the future goals of nuclear energy, in particular for what concerns an improved sustainability, an inherent safety with strong negative temperature coefficient of reactivity, stable coolant, low pressure operation that don not require expensive containment, easy to control, passive decay heat cooling and unique characteristics in terms of actinide burning and waste reduction, while benefiting from the past experience acquired with the molten salt technology. As the only liquid-fueled reactor concept, the safety basis, characteristics and licensing of an MSR are different from solid-uranium fueled light water reactors. In this paper, a historical review of the major plant systems in MSR is presented. The features of different safety characteristics of MSR power plant are reviewed and assessment in comparison to other solid fueled light water reactors LWRs.