Actinide valences in borosilicate glass

The valence states of 238U, 237Np, 239Pu, and 241Am have been studied over a period of time after initial incorporation into a low-titanium borosilicate glass. Under the air-firing conditions used, only the following valence states were observed: U(VI), Np(IV), Pu(IV), and Am(III). Over a period of one year, no actinide valence changes were observed. Preliminary EXAFS studies on uranium- and thorium-doped glasses indicate ordering in the first coordination shell of the actinide ions, with apparent local structure resembling that existing in model crystalline compounds. (orig.)