PNNL

Abstract

Four promising iodine “getter” materials (Ag, Cu, Bi, Sn) for radioiodine capture were assessed in their pure metal-iodide (MIx) pellet forms to compare their relative durabilities. To study chemical durability, commercial MIx compounds of AgI, BiI3, BiOI, CuI, and SnI4 were converted to dense, monolithic pellets using spark plasma sintering. Semi-dynamic leach testing in the form of a modified ASTM-C1308 test was then performed on the pellets in two different forms including unmounted (as-pressed) specimens and epoxy-mounted specimens with polished surfaces. The corrosion testing results and sample characterizations showed that three of the five MIx compounds tested (i.e., AgI, CuI, and BiOI) displayed high leach resistances. While the remaining two MIx compounds (i.e., BiI3 and SnI4) are desirable due to their high potential iodine loading capacities, they both readily decomposed during leach testing, indicated by crystallographic changes in the specimens as well as large amounts of iodine detected in the leachate solutions. The instabilities of BiI3 and SnI4 raise uncertainties for their candidacies as viable waste forms for radioiodine following capture by the “getters”.