Dual phase magnesia-zirconia ceramics doped with plutonia and erbia are being evaluated as an inert matrix fuel (IMF) for light water reactors (LWR). The motivation for this work is to develop an IMF with a thermal conductivity superior to that of the fuels based on single-phase yttria stabilized zirconia. The innovative fuel developed at INL is comprised of two major phases: pure MgO and quaternary solid solution consisting of MgO, ZrO{sub 2}, Er{sub 2}O{sub 3} and PuO{sub 2}. Pure MgO phase acts as an efficient heat conductor. It has been shown [1] that dual phase MgO-ZrO{sub 2} ceramics have the thermal conductivity superior to that of UO{sub 2} and have notable chemical resistance to water at the temperature of 573 K and pressure 8.6 MPa, which makes them attractive for use as an IMF matrix in LWRs
