Graphite-filled mixed-oxide fuel design for fully loaded PWR cores

Abstract

In order to maximize the benefit of plutonium recycling in the current light water reactor (LWR) cores, recently, many researches have been performed for 100% mixed-oxide (MOX) core. However, when the LWR core is fully loaded with MOX fuel, several problems arise due to the spectrum hardening effect of the plutonium isotopes. In order to overcome the spectrum hardening effect, we propose a new fuel design for full MOX core, that consists of annular fuel material filled internally with graphite. The new design is compatible with the conventional assembly in its overall geometry, and therefore it may require only minor modifications from the conventional fuel technology. The results of assembly and core analysis with the graphite-filled MOX fuel rods indicate that the new fuel design provides desirable characteristics, namely, higher burnup with less fuel inventory, faster depletion of plutonium and less production of actinides, and better safety features in fuel temperature, control rod worth, boron worth, moderator temperature coefficient (MTC), and shutdown margin. These beneficial results come from the enhanced moderation of the neutrons due to the moderating power of graphite and its contribution to the increased moderator/fuel volume ratio.