The properties of a standard UO2 fuel and three SIMFUEL materials (uni
rradiated analogues of used nuclear fuels) have been characterized ele
ctrochemically and under natural corrosion conditions. The general oxi
dation and reduction behaviour was determined voltammetrically. The ef
fect of substituents on the surface reactivity was determined by study
ing the electroreduction of O-2 Under natural corrosion conditions, SI
MFUELs oxidize more rapidly than does UO2, but then appear to dissolve
at a similar rate.