Immobilization of spent nuclear fuel in iron phosphate glass

Twenty-four iron phosphate compositions (15 wt% wasteloading) were evaluate d to determine their suitability for vitrifying AI-clad, highly enriched ur anium, spent nuclear fuel (SNF). In half the compositions melted, 80 wt% of the Al2O3 in the simulated SNF was removed prior to vitrification. All twe nty-four compositions formed homogeneous glasses, many at temperatures as l ow as 1150 degrees C. As little as 2.5 wt% Na2O decreased melt viscosity an d increased alumina solubility in those glasses of higher alumina contents (7.2 wt% Al2O3). None of the glasses contained undissolved uranium compound s as has been found in borosilicate glasses containing as little 4.4 wt% UO 2. The chemical durability (measured by the product consistency test (PCT)) of the iron phosphate wasteforms is as good as, and in many cases up to 15 times better than the approved reference material(ARM-l) borosilicate glas s. (C) 1999 Published by Elsevier Science B.V. All rights reserved.