Investigation of core parameters and fuel cycle scenarios for molten salt thorium reactors

In the context of the thesis presented, scenarios for fuel cycles containing Thorium (Th) have been investigated for Molten Salt Reactors (MSRs), proposed as one of the Generation IV nuclear reactor types. Initially, an original software was developed in Python for conducting burnup analyses. The burnup module of the developed software was validated against OECD/NEA benchmark studies. Utilizing the software with added reprocessing capability, which is not found in the traditional burnup codes, based on the unit cell model derived from the MSBR design, burnup simulations were performed with various fuel compositions containing Th-232. By these simulations, effects of using Uranium-235 (U-235) instead of U-233 and small changes in the Th-232 fraction in the initial fuel load were investigated and scenarios were explored where the criticality could be sustained leading high burnup values, achieved solely with Th-232 without any fissile material added externally. Using highly enriched (%93,3) U in the first fuel load, with the scenario where fission products are regularly separated from the fuel salt with respect to their "cycle times" and Pa-233 is also separated from the fuel, stored in a tank for a certain period and then fed back to the fuel; the criticality can be maintained in a self-sufficient way and burnup values as high as 800 GW-day/MTHM can be reached. Despite being dependent on several conditions and factors, the achievable burnup value is 15-20 times higher than that of the traditional reactors.