Neutronic analysis of dual fluid reactors

The aim of this study is to investigate the neutronic behavior of reactors in the Dual Fluid Reactor (DFR) designs, specifically the DFRs and DFRm concepts, using various fuels and materials. For the DFRs concept, ThCl4-PuCl3 and NaCl-ThCl4-PuCl3 fuel salts have been proposed. Additionally, the geometry of the silicon carbide (SiC) fuel tube has been modified, and the reactor's neutronic behavior has been analyzed with yttrium hydride (YH1.85) and magnesium oxide-beryllium oxide (MgO-BeO) materials. A thermal DFRs reactor has been achieved by adding 0.05 cm thick YH1.85 to the fuel tube. To extend the fuel lifespan and simplify the fuel reprocessing process, a ThCl4-PuCl3 blanket has been proposed. The results show that the ThCl4-PuCl3 blanket prolongs fuel life and achieves positive temperature coefficients. Future optimization of compositions with negative temperature coefficients may be possible. In the DFRm concept, U-Mn and U-Fe fuels with lower melting points have been suggested instead of U-Cr. U-Mn fuel exhibits similar behavior to U-Cr fuel, thereby extending the operating temperature range of the DFRm reactor and achieving the same fuel lifespan as with U-Cr fuel. Although U-Fe fuel results in a shorter fuel cycle life due to its lower fissile content, its negative temperature coefficients make it a potential candidate for reference DFRm reactors. Additionally, the behavior of MgO-BeO ceramic moderator materials has been examined as a replacement for SiC in DFRm. While MgO-BeO shows similar neutronic behavior to SiC, it has a positive moderator coefficient in BOL when using U-Fe fuel. Given its lower thermal conductivity compared to SiC, SiC is recommended as the fuel tube material for both fuels. Overall, the DFRm concept shows promise for micro reactor design due to its high power density, long fuel life, and compact structure. The findings provide a basis for optimizing fuel and blanket compositions.