Oxygen redistribution in LMFBR fuels

The behavior of oxygen in hypostoichiometric mixed oxide fuels in a temperature gradient is discussed from experiments performed out-of-pile. Oxygen migration toward the cold end of the temperature gradient has been consistently observed. However, the degree of distribution, characterized by the heat of transport, is a function of the over all stoichiometry and the Pu content of the fuel. An empirical relation between the heat of transport and the over-all stoichiometry of typical LMFBR oxide fuels has been formulated and used to predict the O-to-M profile under a given set of irradiation conditions. Cladding oxidation imposes an additional constraint and must be properly accounted for in predicting O-to-M profiles. Other reactions involving fission products may influence the O-to-M profile under certain conditions