On the Use of a Molten Salt Fast Reactor to Apply an Idealized Transmutation Scenario for the Nuclear Phase Out

In the view of transmutation, molten salt fast reactors (MSFRs) offer certain advantages compared to solid fuelled reactor types. In the first part these advantages are discussed in comparison with the sodium cooled fast reactor technology, and the research challenges are analyzed. In the second part cycle studies for the MSFR are given for different configurations – a core with U-238 fertile, a fertile free core, and a core with Th-232 as a fertile material. For all cases, the transmutation potential is determined, and a significant improvement in the transmutation performance for the case with thorium as a fertile material is demonstrated. The time evolution of different important isotopes is analyzed. In the third part a strategy for the optimization of the transmutation efficiency is developed. The final aim is dictated by the phase out decision of the German government, which requests to put the focus on the determination of the maximal transmutation efficiency and on an as much as possible reduced left over of transuranium elements at the end of the reactor life. This minimal left over is achieved by a second deep burning phase. There the U-233, which is bred in the blanket of the core, is used as feed. It is demonstrated, that transmutation rates up to more than 90% can be reached, while the production of undesired high elements like californium is very limited. Additionally, the adaptations needed for the simulation of a MSFR, and the used tool HELIOS 1.10 are described.