46 Search Results

The increasing reliance on nuclear energy as a significant low-carbon power source necessitates effective solutions for managing radioactive emissions. This study introduces a novel application of MXene nanohybrids, specifically silver-MXene (Ag-Ti₃C₂T_x), as an effective sorbent for radioiodine off-gas capture at an operating temperature of 150 °C. Through comprehensive material characterization, including X-ray diffraction, scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, Raman spectroscopy, thermogravimetric analysis, inductively coupled plasma optical emission spectroscopy, and gas sorption analyses, the successful loading of Ag nanoparticles onto Ti₃C₂T_x is confirmed and the subsequent formation of AgI upon iodine capture. The results demonstrate that Ag-Ti₃C₂T_x exhibitsmore » superior iodine uptake compared to traditional silver-based sorbents such as silver mordenite zeolite (AgZ) and silver-functionalized silica aerogel (AgAero). The Ag-Ti₃C₂T_x achieves an iodine loading of 946 mg g⁻¹, significantly outperforming AgZ (131 mg g⁻¹). These findings highlight the potential of Ag-Ti₃C₂T_x as a highly efficient, thermally stable sorbent for radioiodine capture, and potentially addressing key limitations of existing materials.« less

Here, waste forms containing glassy and crystalline phosphate and silicate phases were produced to immobilize salt waste simulants from pyroprocessing and characterized by using Raman spectroscopy, Mössbauer spectroscopy, X-ray diffraction, scanning electron microscopy, heat capacity, and chemical durability measurements. In this work, a phosphosilicate waste form is presented to leverage the benefits of both borosilicate glasses and iron phosphate glasses. To improve waste loading, prior to immobilization, salt simulants were successfully dechlorinated using ammonium dihydrogen phosphate, mixed with a borosilicate frit (5–30 wt %) and Fe₂O₃, and vitrified. Additions of 2.5–15 wt % borosilicate glass (NBS3) improved normalized release ratesmore » for Cs relative to iron-phosphates without NBS3, resulting in chemical durabilities similar to high-level waste borosilicate glass reference materials. The release rates of the alkalis (i.e., Li, Na, K, Cs) were the lowest with the addition of 5 wt % NBS3. Although Sr was not specifically targeted in this study, evidence exists that it preferentially partitioned with Si to form an amorphous droplet phase within the iron phosphate glass matrix.« less

Designing sorbents for iodine capture in different conditions requires selection and optimization of a large and diverse range of variables. These variables fall into general categories (or features) of sorbent activity, sorbent stability, and the fate of the loaded material in terms of the disposal (waste form) options available. To illustrate, silver-loaded, high-porosity sorbents make for maximized iodine capture and less pressure drop in a column-based sorption system approach, however, this high porosity can lead to less mechanically stable sorbents. Additionally, waste forms containing silver must also be compliant with additional criteria for hazardous waste disposal. Thus, all these aspectsmore » must be considered simultaneously when selecting a sorbent for utilization under specific conditions. Information is given for different types of sorbent design considerations for different operating conditions and some emphasis is also given on promising alternatives for silver as the active (chemisorption-based) getter metal. Discussion is given around demonstrated options for waste forms for different metal-iodide compounds.« less

Four promising iodine “getter” materials (Ag, Cu, Bi, and Sn) for radioiodine capture were assessed in their pure metal-iodide (MI_x) pelletized forms to compare relative chemical durabilities. To study chemical durability, commercial MI_x compounds of AgI, BiI₃, BiOI, CuI, and SnI₄ were converted to dense monolithic pellets using spark plasma sintering. Semidynamic leach testing in the form of modified ASTM C1308 tests was then performed on the pellets in two different forms including unmounted (as-pressed) specimens (i.e., “U”) and epoxy-mounted specimens (i.e., “M”) with polished surfaces. The chemical durability results and sample characterizations showed that three of the five MI_xmore » compounds tested (i.e., AgI, CuI, and BiOI) displayed moderate to high leach resistances. Further, the remaining two MI_x compounds (i.e., BiI₃ and SnI₄), which are both desirable iodine waste forms due to their high iodine loading capacities, 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 using the base metals/cations (i.e., Bi⁰/Bi³⁺ and Sn⁰/Sn⁴⁺, respectively) as viable getters for radioiodine capture due to likely poor waste form chemical durabilities after capture and consolidation into waste forms.« less

The synthesis methods, crystal structures, and properties of anhydrous monazite and xenotime (REPO₄) crystalline materials are summarized within this review. For both monazite and xenotime, currently available Inorganic Crystal Structure Database data were used to study the effects of incorporating different RE cations on the unit cell parameters, cell volumes, densities, and bond lengths. Domains of monazite-type and xenotime-type structures and other AXO4 compounds (A = RE; X = P, As, V) are discussed with respect to cation sizes. Reported chemical and radiation durabilities are summarized. Different synthesis conditions and chemicals used for single crystals and polycrystalline powders, as wellmore » as first-principles calculations of the structures and thermophysical properties of these minerals are also provided.« less

Phosphate glasses have a range of applications including as hosts for immobilizing radioactive wastes. Studies have shown that addition of iron and/or aluminum oxides can drastically improve the chemical durability of phosphate glasses where the accurate measurement of chemical durability is one of the most important factors for determining the long-term viability of a given waste form. However, due to inconsistencies with the experimental methods used to generate chemical durability data, comparing and interpreting such data is a tedious task. These variables include the temperature of the test, the specimen form (e.g., coupon, particles), the pressure of the test (e.g.,more » atmospheric pressure, elevated pressure in an autoclave), the exposure time, the exposure medium, and how the loss is documented (e.g., total mass lost, normalized elemental release). This review paper summarizes a large collection of chemical durability tests on aluminophosphate glasses in various studies. In addition, the effects of different oxides on the properties of phosphate glasses are summarized.« less

This work demonstrates polyacrylonitrile composites for iodine capture using promising metal-sulfide (Ag ₂ S, Bi ₂ S ₃ , Cu ₂ S) compounds as the active gettering agents.

Different sorbents, including activated carbons, an aerogel, xerogels, an alumina, a zeolite, and a carbon foam were investigated for static I _2(g) loading at 71 °C for 56 d followed by 4.7 d of desorption.