In providing nuclear power plant safety the priority is currently given to reactor self-protection by means of inherent features and passive means. The problems of self-protection for molten-salt fuel reactor (MSR) and molten-salt cooled coated particle fuel graphite reactor (HTMSR) have been studied. The following ways to reach a high level of self-protection are investigated: a) high level of natural circulation (100% for MSR and 10% for HTMSR); b) integrated layout; c) minimization of reactivity changes during fuel burn-up; d) decrease of maximum operative temperature. Calculations of transient processes during heavy accidents without scram are presented. It is shown that maximum temperatures of the primary circuit materials do not reach critical values under such accidents. For the high hypothetical case with the damage of the reactor and guard vessels in MSR the fission products yield from the fuel salt into gas-phase of MSR containment is investigated.