Molten Salt Reactor (MSR) is a family of Gen IV nuclear fission reactor in which the fuel is dissolved in a molten salt. Fast chloride MSR is considered as a promising way to close the current French fuel cycle by burning minor actinides produced by nuclear power plants. Indeed, chloride salts properties offer a harder neutron flux and higher actinides solubility which permits to transmute larger amounts of minor actinides in comparison to fluorides salts. The ARAMIS-A concept, designed and studied in the frame of the ISAC (Innovative System for Actinide Conversion) project, belongs to this category. Decay heat is one of the topics studied in the ISAC project. Decay heat is the heat produced by a nuclear power plant after shutdown, mostly coming from depleted fuel and other materials radioactivity as well as residual fissions. To calculate decay heat, a new code, CEREIS, coupled to depletion code SERPENT2 has been developed. CEREIS operation process will be presented together with calculation results and outlooks. Decay heat removal is essential to ensure fuel envelope integrity during planned or unplanned reactor shutdown, used fuel and waste treatments, transport and storage. Yet, in the case of MSR, the dispersible aspect of the liquid fuel and possible on-line fuel treatment can lead to several locations, so several decay heat source terms and then several decay heat removal (DHR) systems. Therefore, to fulfill an adequate DHR function reliability, safety analyses with the Lines of Defence method have been applied to identify required fuel salt locations and DHR systems. Results of these analyses and outlooks will be presented.