X-RAY PHOTOELECTRON-SPECTRA OF SIMFUEL

An X-ray photoelectron spectroscopy (XPS) study of SIMFUEL, an unirrad iated analogue of high-burnup UO2 fuel, was conducted. This paper repo rts a revised composition for SIMFUEL with 6 at.% burnup. XPS spectra indicate that the uranium atoms are mainly in the U4+ state, with the U6+-to-U4+ ratio being less than 0.005. The oxidation state of the dop ant elements is discussed: Ru, Rh, Mo and Pd are present in the metall ic state, whereas Sr, Ba, Y, La, Zr and Ce are present as oxides. Beca use of low signal intensity, the oxidation state of Nd could not be de termined.