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The supply chain for metal powders used in additive manufacturing (AM) is currently experiencing exponential growth and with this growth come new powder suppliers, new powder manufacturing methods and increased competition. The high number of potential supply chain options provides AM service providers with a significant challenge when making decisions on powder procurement. This paper provides an overview of the metal powder supply chain for the AM market and aims to give AM service providers the information necessary to make informed decisions when procuring metal powders. The procurement options are categorised into three main groups, namely: procuring powders from AM equipment suppliers, procuring powders from third party suppliers and procuring powders directly from powder atomisers. Each of the procurement options has its own unique advantages and disadvantages. The relative importance of these will depend on what the AM equipment is being used for, for example research, rapid prototyping or productionisation. The future of the metal AM powder market is also discussed.

The aragonitic skeletons of massive corals (Scleractinia) are commonly used as biological and paleoenvironmental archives based on their annual density banding. In case of high-resolution proxy studies, however, taxon-specific biases related to the skeletal architecture of the selected coral species can occur, which may impact the resulting skeletal growth chronologies. This study focusses on the quantification of high-resolution skeletal density records in the massive starlet coral Siderastrea siderea from a nearshore reef environment at the southern coast of Belize (western Caribbean Sea) by using two-dimensional grid-scanning americium-241 ( 241 Am) gamma densitometry. Multiple linear sample pathways were systematically selected through central corallite areas (i.e., around the columella) and the corresponding walls (synapticulotheca) of contemporaneously formed corallites in S. siderea . By following this approach, annual density banding (or distortions in its formation) can be identified and related to the general architectural elements and/or to variations in the longitudinal alignment of corallites. The demarcation of high-density bands is often more clearly developed in the corallite walls than around the columella. Therefore, future high-resolution linear skeletal density chronologies should be established based on the more robust corallite walls to reduce such biases in density banding of S. siderea corals.

Micronuclear batteries harness energy from the radioactive decay of radioisotopes to generate electricity on a small scale, typically in the nanowatt or microwatt range 1 , 2 . Contrary to chemical batteries, the longevity of a micronuclear battery is tied to the half-life of the used radioisotope, enabling operational lifetimes that can span several decades 3 . Furthermore, the radioactive decay remains unaffected by environmental factors such as temperature, pressure and magnetic fields, making the micronuclear battery an enduring and reliable power source in scenarios in which conventional batteries prove impractical or challenging to replace 4 . Common radioisotopes of americium ( 241 Am and 243 Am) are α-decay emitters with half-lives longer than hundreds of years. Severe self-adsorption in traditional architectures of micronuclear batteries impedes high-efficiency α-decay energy conversion, making the development of α-radioisotope micronuclear batteries challenging 5 , 6 . Here we propose a micronuclear battery architecture that includes a coalescent energy transducer by incorporating 243 Am into a luminescent lanthanide coordination polymer. This couples radioisotopes with energy transducers at the molecular level, resulting in an 8,000-fold enhancement in energy conversion efficiency from α decay energy to sustained autoluminescence compared with that of conventional architectures. When implemented in conjunction with a photovoltaic cell that translates autoluminescence into electricity, a new type of radiophotovoltaic micronuclear battery with a total power conversion efficiency of 0.889% and a power per activity of 139 microwatts per curie (μW Ci −1 ) is obtained. A micronuclear battery is built based on an autoluminescent americium–terbium compound that couples radioisotopes with energy transducers at the molecular level, resulting in an 8,000-fold enhancement in energy conversion efficiency.

Diethylenetriaminepentaacetic acid (DTPA) is currently still the only known chelating drug that can be used for decorporation of internalized plutonium (Pu) and americium (Am). It is generally assumed that chelation occurs only in biological fluids, thus preventing Pu/Am deposition in target tissues. We postulate that actinide chelation may also occur inside cells by a mechanism called “intracellular chelation”. To test this hypothesis, rats were given DTPA either prior to (termed “prophylactic” treatment) or belatedly after (termed “delayed” treatment) Pu/Am injection. DTPA decorporation efficacy was systematically tested for both plutonium and americium. Both prophylactic and delayed DTPA elicited marked decreases in liver Pu/Am. These results can be explained by chelation within subcellular compartments where DTPA efficacy increased as a function of a favorable intracellular DTPA-to-actinide molar ratio. The efficacy of intracellular chelation of liver actinides decreased with the delay of treatment. This is probably explained by progressive actinide binding to the high-affinity ligand ferritin followed by migration to lysosomes. Intracellular chelation was reduced as the gap between prophylactic treatment and contamination increased. This may be explained by the reduction of the intracellular DTPA pool, which declined exponentially with time. Skeletal Pu/Am was also reduced by prophylactic and delayed DTPA treatments. This decorporation of bone actinides may mainly result from extracellular chelation on bone surfaces. This work provides converging evidence for the involvement of an intracellular component of DTPA action in the decorporation process. These results may help to improve the interpretation of biological data from DTPA-treated contamination cases and could be useful to model DTPA therapy regimens.

The uptake of 241 Am, 244 Cm and 249 Cf with LN resin was studied in HCl and HNO 3 solutions with concentrations ranging from 0.02 to 2.5 M. There is high uptake at concentrations < 0.1 M in both acids for all three isotopes with decreasing uptake at higher concentrations and negligible extraction at ≥ 0.6 M. Californium has a higher extraction than americium and curium, which are extremely similar. Kinetics studies showed rapid uptake of all three isotopes. Column studies were performed to demonstrate the separation of 241 Am and 249 Cf, and a bulk separation including nine stable lanthanides along with 241 Am, 249 Cf, and 88 Y.

Selective oxidation of trivalent americium (Am) could facilitate its separation from lanthanides in nuclear waste streams. Here, we report the application of a high-surface-area, tin-doped indium oxide electrode surface-derivatized with a terpyridine ligand to the oxidation of Am(III) to Am(V) and Am(VI) in nitric acid. Potentials as low as 1.8 volts (V) versus the saturated calomel electrode were applied, 0.7 V lower than the 2.6 V potential for one-electron oxidation of Am(III) to Am(IV) in 1 molar acid. This simple electrochemical procedure provides a method to access the higher oxidation states of Am in noncomplexing media for the study of the associated coordination chemistry and, more important, for more efficient separation protocols.

Partitioning of americium from lanthanides (Ln) present in used nuclear fuel plays a key role in the sustainable development of nuclear energy 1 – 3 . This task is extremely challenging because thermodynamically stable Am(III) and Ln(III) ions have nearly identical ionic radii and coordination chemistry. Oxidization of Am(III) to Am(VI) produces AmO 2 2+ ions distinct with Ln(III) ions, which has the potential to facilitate separations in principle. However, the rapid reduction of Am(VI) back to Am(III) by radiolysis products and organic reagents required for the traditional separation protocols including solvent and solid extractions hampers practical redox-based separations. Herein, we report a nanoscale polyoxometalate (POM) cluster with a vacancy site compatible with the selective coordination of hexavalent actinides ( 238 U, 237 Np, 242 Pu and 243 Am) over trivalent lanthanides in nitric acid media. To our knowledge, this cluster is the most stable Am(VI) species in aqueous media observed so far. Ultrafiltration-based separation of nanoscale Am(VI)-POM clusters from hydrated lanthanide ions by commercially available, fine-pored membranes enables the development of a once-through americium/lanthanide separation strategy that is highly efficient and rapid, does not involve any organic components and requires minimal energy input. A new strategy to separate radioactive americium from lanthanides based on complexation with polyoxometalates and ultrafiltration technique is highly efficient and rapid, does not involve any organic components and requires minimal energy input.

Luffa cylindrica biomass was converted to biochar and the removal of [sup.241]Am by pristine and oxidized biochar fibers was investigated in laboratory and environmental water samples. This species has the added advantage of a unique microsponge structure that is beneficial for the production of porous adsorbents. The main purpose of this study was to valorize this biomass to produce an efficient adsorbent and investigate its performance in radionuclide-contaminated waters. Following the preparation of Am[sup.3+] solutions at a concentration of 10[sup.−12] mol/L, the adsorption efficiency (K[sub.d]) was determined as a function of pH, adsorbent mass, ionic strength, temperature, and type of aqueous solution by batch experiments. At the optimum adsorbent dose of 0.1 g and pH value of 4, a log[sub.10]K[sub.d] value of 4.2 was achieved by the oxidized biochar sample. The effect of temperature and ionic strength indicated that adsorption is an endothermic and entropy-driven process (ΔH° = −512 kJ mol[sup.−1] and ΔS° = −1.2 J K[sup.−1] mol[sup.−1]) leading to the formation of inner-sphere complexes. The adsorption kinetics were relatively slow (24 h equilibrium time) due to the slow diffusion of the radionuclide to the biochar surface and fitted well to the pseudo-first-order kinetic model. Oxidized biochar performed better compared to the unmodified sample and overall appears to be an efficient adsorbent for the treatment of [sup.241]Am-contaminated waters, even at ultra-trace concentrations.

The behavior of 88 Y, 152 Eu, 228 Ac, 241 Am, and 244 Cm was studied with 2-thenoyltrifluoroacetone resin with batch uptake, kinetics and column studies. Studies were performed in acetate buffer solutions (pH ~ 2 to ~ 6) and there was high uptake of all isotopes, except 228 Ac, at pH > 4.5. The kinetics of uptake were reasonable, although slower for the actinides, and sufficient for column studies. The retention of 88 Y, 152 Eu, and 241 Am on the resin in column studies was demonstrated as well as a reasonable separation of these isotopes from 228 Ac.

This paper reports the activity concentrations of 137 Cs, 90 Sr, 239+240 Pu, 241 Am, and 3 Н in the form of tritiated water (НТО) and organically bound tritium (ОBТ) in the tissues and organs of roe deer ( Capreolus pygargus Pal., 1771) that inhabit the ‘Degelen’ test location of the Semipalatinsk Test Site. Tissues and organs were sampled from six deer by killing. The activity concentrations of specific radionuclides in the samples were measured using γ-, α-, and β-spectrometry. The radionuclide activity concentrations in the tissues and organs showed considerable variation, for example, 0.6–170 Bq kg -1 for 137 Cs and 0.3–2.8×10 3 Bq kg -1 for 90 Sr. The activity concentrations of radionuclides in animal muscular tissue did not exceed permissible values for the meat of wild animals. The tissues and organs in the roe deer were arranged as follows in descending order of their ability to accumulate 137 Cs and 90 Sr: for 137 Cs, muscular tissue–kidneys–lungs–spleen–heart–liver–bone tissue; for 90 Sr, bone tissue–liver–lungs–muscular tissue–spleen–heart–kidneys. The activity concentrations of 241 Am and 239+240 Pu did not exceed the minimum detectable activity. Therefore, no quantitative values could be determined for 241 Am, and the 239+240 Pu activity concentration could be derived for only one sample: 0.5±0.1 Bq kg -1 (liver). The distribution pattern of these radionuclides in the tissues and organs of the roe deer could not be determined because of insufficient data. The HTO volumetric activity in the tissues and organs of the examined animals ranged from 2.6×10 −2 to 77 kBq l -1 ; activity concentration of OBT, 3.0×10 −2 to 16 kBq kg -1 ; and OBT-to-HTO ratios, 2.0×10 −3 to 5.3×10 2 . This ratio can serve as an indicator of how long the examined animals stay in radioactively contaminated ecosystems. Within the ‘Degelen’ site, the activity concentrations of 90 Sr and tritium, in the form of HTO and OBT, are expected to be high in the bone tissues, soft tissues, and organs, respectively.