New measurements on (U,Pu)O2 properties within European projects: ESNII+ and ESFR-SMART

A set of oxide fuel properties is needed to develop the fast neutron systems and to design prototypes of the Sodium Fast Reactor, the Gas-cooled Fast Reactor and a heavy liquid metal cooled Accelerator Driven System. The ESNII+ project (2014-2017) and then ESFR-SMART project (2017-2022) have a work package dedicated to this item : providing thermal and mechanical properties of MOX fuel through a catalog and performing complementary measurements on specific properties. The data and models available in the literature for each property were reviewed and experimental workplan was proposed for the European projects mentioned. Property measurements are done on existing fresh and irradiated fuel samples, identified to cover the fuel characteristics in term of plutonium content, density, stoichiometry, temperature and burn-up. Measurements have been performed and are continuing on thermal diffusivity, heat capacity, melting temperature, thermal expansion and Young modulus. The paper presents the results obtained on properties measurements and the comparison with existing and available data.