  A re-evaluation of the Molten Salt Breeder Reactor concept has revealed
problems related to its safety and to the complexity of the reprocessing
considered. A reflection is carried out anew in view of finding innovative
solutions leading to the Thorium Molten Salt Reactor concept. Several main
constraints are established and serve as guides to parametric evaluations.
These then give an understanding of the influence of important core parameters
on the reactor's operation. The aim of this paper is to discuss this vast
research domain and to single out the Molten Salt Reactor configurations that
deserve further evaluation.
