Iron polyphosphate glasses for waste immobilization

Abstract

Iron polyphosphate glasses resist attack by water, can dissolve large concentrations of species that are otherwise insoluble in borosilicate glass melts, and can be processed at relatively low temperatures (1000‐1200°C), and so are viable hosts for vitrifying hazardous and radioactive wastes. The properties of iron polyphosphate glasses depend on the distributions of phosphate anions and the nature of the bonds between those anions and various metal polyhedra, and quantitative information can be obtained about those structures using a variety of spectroscopic, diffraction, and chromatographic techniques. This structural information helps explain compositional trends in properties, including dissolution rates, electrical conductivity, thermal properties and crystallization tendency. Studies of waste forms made with low activity and high level wastes are reviewed and related back to an understanding of the structures and properties of simpler iron polyphosphate glasses.

Formation of Reaction Layer and Dissolution Behavior of Alkali and Alkaline-Earth Iron Phosphate Glasses in Water

“…6) Figure 4 shows the normalized mass release data of all cationic elements for the 15NaIP35, 15KIP35, 20CaIP35, and 20BaIP35 glasses. All NR i values are over two orders of magnitude lower than the United States Department of Energy (DOE) requirements for both high-and low-level activity wastes, 9,10) as shown in Table 1. All glasses released cations preferentially in the order R or RA > P º Fe, where R = Na, K and RA = Ca, Ba.…”

Vitrification of wastes: from unwanted to controlled crystallization, a review

“…Alternative host matrices, such as the iron phosphate glasses [Stefanovsky et al, 2017a] and lead iron phosphate glasses [Sales and Boatner, 1984], can offer a way of overcoming these shortcomings, since phosphate glasses have a much higher solubility for constituents such as halides, molybdenum, and zirconium. Research has suggested that iron phosphate waste forms can increase radioactivity concentrations (>2× greater) that can be safely stored and thereby decrease the total nuclear waste volume (>2× smaller) for storage and disposal [Brow et al, 2020]. However, phosphate glasses are known to react unfavorably with refractory materials [Tracy et al, 2021] including electrodes used in Joule-heated melters [National Research Council, Committee on Waste Forms Technology and Performance, 2011].…”

Effect on structure, stability, and H+ irradiation on Nd3+/Ru4+‐loaded iron phosphate glass for nuclear applications

“…Compared to borosilicate glass that is the most common nuclear waste vitrification matrix, iron phosphate glass (IPG) has lower melting temperatures and also higher waste loading capacity of sulfates, phosphates, chlorides, various heavy metals as well as chromium oxides 1,2 . However, its practical application is limited because the information on the loading of various nuclear waste components in IPG has not been studied extensively 3 . The 40Fe 2 O 3 –60P 2 O 5 stoichiometry of IPG has been optimized based on its chemical stability for nuclear waste loading.…”

“…The 40Fe 2 O 3 –60P 2 O 5 stoichiometry of IPG has been optimized based on its chemical stability for nuclear waste loading. It has a low melting temperature of ∼945°C and causes a lower extent of corrosion in the Inconel alloys and oxide refractory materials used in the vitrification process, which improves the lifetime of the melter 3–6 . The structure of IPG consists of a network of phosphate (mono‐, di‐, and tri‐forms) anions linked by tetrahedrally and octahedrally coordinated iron oxide.…”

“…The structure of IPG consists of a network of phosphate (mono‐, di‐, and tri‐forms) anions linked by tetrahedrally and octahedrally coordinated iron oxide. The resultant Fe–O–P linkages are less susceptible to hydration and hence render chemical durability to the glassform 3 . The composition of nuclear waste includes actinides like U, Pu, Am, Cm, fission elements (mainly Cs, Xe, I, Ru), and various other α‐/β‐/γ‐ray emitting radionuclides.…”