Swelling of Uranium Dioxide–Silumin Dispersion Fuel Composition in Experimental Fuel Elements of the SM Reactor

A variant of experimental dispersion fuel elements with a displacer and uranium dioxide-silumin fuel composition, which were proposed for modernizing the core of the SM reactor, was investigated. The fuel elements were irradiated in a wide spectrum of neutron- and thermophysical parameters of the reactor's reflector channel. The fuel elements showed satisfactory radiation resistance at thermal flux density 5.8–8 MW/m² and burnup to 45%. The swelling of the fuel composition was analyzed. It is shown that of three possible components of the swelling the one due to gaseous fission products makes the main contribution, approximately 3/4 of the total amount. The interaction of the fuel components results in compaction of the kernel and promotes some compensation of the swelling, increasing as the interaction increases. These investigations show that the depth of burnup at the achieved thermal flux density for fuel elements with a displacer is not the limit.