Oxygen potential measurements on irradiated oxide nuclear fuel

A method has been developed whereby direct data on the radial variation of oxygen potential in an oxide fuel pin can be determined. The method uses a miniature solid state galvanic cell which enables emf measurements to be made on micro samples extracted from different radial positions in the fuel pin. Measurements have been made on a pin irradiated in the Dounreay Fast Reactor to ~6 % burn-up. The oxygen gradient deduced from the experimental results was smaller than that predicted theoretically although the mean O/M was within the manufacturing tolerances of the fuel pin. During the testing of the galvanic cell, new data were obtained for the relationship between oxygen to metal ratio and oxygen potential for hypostoichiometric uranium, plutonium oxide. Some anomalous results from these experiments, arising from inhomogeneities in the sample, have been interpreted as an explanation for discrepancies in the published data for this system. © 1979.