Local structure around actinides in borosilicate glasses

X-ray absorption and optical absorption spectroscopy have been used to study the valence state and local structure of uranium and thorium in borosilicate glasses. Glasses of composition similar to those studied for the nuclear-waste storage are compared to glasses of simplified composition. Thorium atoms are in the valence state (IV) with an oxygen environment of eight atoms. Uranium is very sensitive to the glass composition. The valence states (IV), (V) and (VI) are simultaneously present and correspond to different local organizations