Investigation of sub-solidus phase relations in some of the ternary systems relevant to inert matrix fuels

Inert matrix fuel is a concept aimed at annihilation of large stocks of available plutonium, thereby producing energy from it. In order to identify newer inert matrices, phase relations were constructed in some relevant systems so as to find out suitable single phasic compositions. As a part of the inert matrix fuel program, several ternary phase relations were established in the oxide systems, CeO2-ThO2-ZrO2, CeO2-Gd2O3-ZrO2, CeO2-W2O3-ThO2, wherein ceria has been used as a surrogate material in place of plutonia. Based on the refinement of the XRD data, several phase regions namely, cubic fluorite type solid solution, C-type solid solution, various biphasic regions and a ternary phase field could be delineated. It was found that tetragonal zirconia could be stabilized in CeO2-ThO2-ZrO2 system whereas cubic zirconia could be stabilized in CeO2Gd2O3-ZrO2/ThO2 systems. Another striking result was the stabilization of room temperature C-type modification of Gd2O3 upto higher temperatures. The potential of zircon host lattices was also explored as inert matrix fuel.