Dense and homogeneous MOX fuel pellets manufactured using the freeze granulation route

Dense and homogeneous MOX fuel pellets manufactured using the freeze granulation route

F. La Lumia, L. Ramond, C. Pagnoux, P. Coste

Abstract

MOX fuels (UO2‐PuO2) are used in light water nuclear reactors of several countries and are also potential candidates for fast neutron reactors. Industrial MOX is currently manufactured by a dry‐route process, involving steps with fine powders. To reduce dusting, enhance MOX powder flow properties and decrease manufacturing scrap rate, a new wet‐route process is investigated: the freeze granulation of concentrated water‐based powder suspensions having optimized rheology and dispersion properties. Highly flowable, dustless and easy‐to‐press MOX granules have been elaborated. Sintering green compacts made of such granules gives highly dense and defect‐free pellets which have a very homogeneous U‐Pu spatial distribution, thus improving the fuel characteristics. Indeed, MOX fuels devoid of large Pu‐rich aggregates are thought to have a better behavior under irradiation in reactors by limiting/preventing the formation of the typical high burnup structure.