Immobilization of CsCl and SrF2 in iron phosphate glass

A large part of the radioactive Cs-137 and Sr-90 stored at the Hanford site is present as CsCl and SrF2.;Attempts to incorporate halides in borosilica te glass often produces immiscibility which is undesirable for immobilizing nuclear materials. Conversely, iron phosphate glasses have been made with up to 26 and 31 mol% CsCl and SrF2, respectively, and up to 34 mol% CsCl an d SrF2 combined. These compositions are melted at temperatures as low as 95 0 degrees C for 2 h and form fluid melts. The low melting temperature of th e iron phosphate wasteforms reduces the probability that radioactive Cs-137 Will vaporize from the melt, which becomes increasingly likely at the high er temperature (greater than or equal to 1150 degrees C) used to melt boros ilicate glasses. Analysis of the glasses produced in this study show that v ery little, if any, Cs and Sr was volatilized from the batches, although th e majority of the halide is released during melting. All of the iron phosph ate glassy wasteforms in the current study had a total ion release in disti lled water of approximately 10 mg/l which is about one tenth that measured for the approved reference material (ARM-1), a reference borosilicate glass . The dissolution rate of the iron phosphate wasteforms in distilled water decreased with increasing iron content. (C) 2000 Elsevier Science Ltd. All rights reserved.