Isotope Separation Research Articles

Methods and Objectives in the Separation of Isotopes

Methods and Objectives in the Separation of Isotopes

Data-driven molecular dynamics simulation of water isotope separation using a catalytically active ultrathin membrane.

Water isotope separation, specifically separating heavy from light water, is a technologically important problem due to the usage of heavy water in applications such as nuclear magnetic resonance, nuclear power, and spectroscopy. Separation of heavy water from light water is difficult due to very similar physical and chemical properties between the isotopes. We show that a catalytically active ultrathin membrane (e.g., a nanopore in MoS2) can enable chemical exchange processes and physicochemical mechanisms that lead to efficient separation of deuterium from hydrogen. The separation process is inherently multiscale in nature with the shorter times representing chemical exchange processes and the longer timescales representing the transport phenomena. To bridge the timescales, we employ a deep learning methodology which uses short time scale ab initio molecular dynamics data for training and extends the timescales to the classical molecular dynamics regime to demonstrate isotope separation and reveal the underlying complex physicochemical processes.

Ion-collection characteristics of photoplasma for atomic vapor laser isotope separator module in electrostatic fields

The laser-based isotope separation process is currently pursued to enrich precursor medical isotopes like lutetium-176 and ytterbium-176. India has successfully produced radionuclide lutetium-177 for clinical use by neutron activation. Atomic vapor laser isotope separation (AVLIS) is used as the enrichment technology. Understanding the physics and technology of processes, like atomic-beam generation, photoplasma production, and ion collection, is essential to designing any AVLIS module. So, a stand-alone research facility was developed before the production plant. This article describes the facility and the experimental and theoretical studies of ion collection in electrostatic fields using barium as the working element. Two types of ion extractors, plate–photoplasma–plate and plate–photoplasma–grid–plate, were designed and fabricated. A model of photo-ion collection in these electrostatic ion extractors was arrived at. Scaling of the initial photo-ion densities and the electric fields is crucial to photoplasma evolution spanning single-particle to collective regimes. Estimates of ion-collection rates of the Indian AVLIS modules for lutetium-176 and ytterbium-176 were carried out. By invoking plasma physics, the technological aspect of producing enriched isotopes was solved by judiciously integrating the atom source, laser system, photoplasma, and ion-extractor geometries. Limitations of the electrostatic ion extractors were also flagged.

Ultra-thin proton conducting carrier layers for scalable integration of atomically thin 2D materials with proton exchange polymers for next-generation PEMs.

Scalable approaches for synthesis and integration of proton selective atomically thin 2D materials with proton conducting polymers can enable next-generation proton exchange membranes (PEMs) with minimal crossover of reactants or undesired species while maintaining adequately high proton conductance for practical applications. Here, we systematically investigate facile and scalable approaches to interface monolayer graphene synthesized via scalable chemical vapor deposition (CVD) on Cu foil with the most widely used proton exchange polymer Nafion 211 (N211, ∼25 μm thick film) via (i) spin-coating a ∼700 nm thin Nafion carrier layer to transfer graphene (spin + scoop), (ii) casting a Nafion film and cold pressing (cold press), and (iii) hot pressing (hot press) while minimizing micron-scale defects to <0.3% area. Interfacing CVD graphene on Cu with N211 via cold press or hot press and subsequent removal of Cu via etching results in ∼50% lower areal proton conductance compared to membranes fabricated via the spin + scoop method. Notably, the areal proton conductance can be recovered by soaking the hot and cold press membranes in 0.1 M HCl, without significant damage to graphene. We rationalize our finding by the significantly smaller reservoir for cation uptake from Cu etching for the ∼700 nm thin carrier Nafion layer used for spin + scoop transfer compared to the ∼25 μm thick N211 film for hot and cold pressing. Finally, we demonstrate performance in H2 fuel cells with power densities of ∼0.23 W cm-2 and up to ∼41-54% reduction in H2 crossover for the N211|G|N211 sandwich membranes compared to the control N211|N211 indicating potential for our approach in enabling advanced PEMs for fuel cells, redox-flow batteries, isotope separations and beyond.

Contrasted redox-dependent structural control on Fe isotope fractionation during its adsorption onto and assimilation by heterotrophic soil bacteria.

Despite the importance of structural control on metal stable isotope fractionation in inorganic and abiotic systems, the link between metal structural changes and related isotopic fractionation during reactions with organic surfaces and live cells remains poorly established. We conducted reversible adsorption of Fe(II) and Fe(III) on the surface of exopolysaccharide (EPS)-rich and EPS-poor Pseudomonas aureofaciens, and we allowed Fe intracellular uptake by growing cells. We analyzed the Fe isotopic composition of the remaining fluid and cell biomass, and compared the isotopic fractionation during adsorption and assimilation reaction with relative changes in Fe structural status between aqueous solution and bacterial cells, based on available and newly collected X-ray absorption spectroscopy (XAS) observations. Iron(III) adsorption onto P. aureofaciens at 2.8 ≤ pH ≤ 6.0 produced an enrichment of the cell surface in heavier isotopes with Δ57Fecell-solution ranging from +0.7 to +2.1‰, without a link to pH in EPS-rich cultures. In contrast, the magnitude of isotopic fractionation increased with pH in EPS-poor cultures. Iron(II) adsorption produced an even larger enrichment of the cell surface in heavier isotopes, by up to 3.2‰, tentatively linked to Fe(III) hydroxide precipitation. Intracellular assimilation of Fe(II) favored heavier isotopes and led to Δ57Fecell-solution of +0.8‰. In addition, Fe(III) cellular uptake produced an enrichment of the bacterial biomass in lighter isotopes with Δ57Fecell-solution of -1‰. The XAS analyses demonstrated the dominance of Fe(III)-phosphate complexes both at the cell surface and in the cell interior. We suggest that heavier isotope enrichment of the cell surface relative to the aqueous solution is due to strong Fe(III)-phosphoryl surface complexes and Fe complexation to ligands responsible for metal transfer from the surface to the inner cell. In case of Fe(II) adsorption or assimilation, its partial oxidation within the cell compartments may lead to cell enrichment in heavier isotopes. In contrast, loss of symmetry of assimilated Fe(III) relative to the aqueous Fe3+ ion and longer bonds of intracellular ions relative to aqueous Fe(III)-citrate or hydroxo-complexes could produce an enrichment of cells in lighter isotopes. The versatile nature of Fe(II) and Fe(III) fractionation without a distinct effect of pH and surface exopolysaccharide coverage suggests that, in natural soil and sedimentary environments, Fe isotope fractionation during interaction with heterotrophic bacteria will be primarily governed by Fe complexation with DOM and Fe redox status in the soil pore water.

Electromigration separation of lithium isotopes with B12C4, B15C5 and B18C6 systems

In the aqueous-organic biphasic electromigration system, the larger cavity size of crown ethers, the weaker binding between crown ethers and Li+, and the lower dissociating voltage of complexes and initial voltage enriching 6Li in the catholyte.

A multi‐method approach for the identification and quantification of water balance components of two lentic small water bodies

AbstractThe protection of the globally widespread lentic small water bodies (LSWB) must be based on detailed knowledge about their hydrological connectivity and water balance. The study aimed to identify and quantify water balance components as well as surface‐groundwater interaction of two LSWB in a characteristic lowland region with a combination of different methods. This includes the collection of hydrological data and the use of bromide and water stable isotopes (δ2H and δ18O) as tracers. With their help, mixing models were established, and daily water balances were assessed. The results show a strong bidirectional interaction of both LSWB systems with shallow groundwater. Bromide and stable isotope tracers allowed for the identification of the most relevant in‐ and outflow sources and pathways. Thereby, isotope data revealed isotopic enrichment typical for open‐water bodies and only minor precipitation inputs mainly relevant at the end of the dry season. Water balance calculations suggested accentuated seasonal dynamics that were strongly influenced by shallow groundwater, which represented large inputs into both LSWB. By that, different phases could be identified, with high inflow rates in winter and spring and decreasing fluxes in summer. In one LSWB, a drainage system was found to have a major impact next to the shallow groundwater interaction. The findings of this research provide detailed insights into the influence and importance of shallow groundwater for LSWB in lowland regions. This impacts the diffuse input of agricultural pollutants into these ecologically important landscape features.

Selective 17O-labeling of silica.

The addition of 17OH2 to silica at room temperature leads to spontaneous hydroxyl oxygen exchange and the selective isotopic enrichment of silanols, as observed using in and ex situ17O NMR. The discovery that silanols are labile alters our understanding of the chemistry of silica surfaces.

Magneto-optical isotope enrichment of potassium-40 with transverse cooling

Magneto-optical isotope enrichment of potassium-40 with transverse cooling

Spectroscopy of neutron-rich nuclei produced by multinucleon transfer reactions at KISS

Properties such as lifetimes and masses of neutron-rich nuclei are key parameters for elucidating the astrophysical rapid neutron capture process (r-process). Due to the lack of experimental nuclear data in the relevant extremely neutron-rich region, especially near and above N = 126, the predictions of theoretical nuclear models are crucial for simulating r-process nucleosynthesis. Experimental studies of the properties and structures of neutron-rich nuclei from near the β stability line up to the r-process path provide important inputs to these theoretical models, improving the accuracy of predictions for the nuclear properties involved in the rprocess. We are developing the KEK Isotope Separation System (KISS) at the RIKEN RIBF facility to produce and separate these nuclei to perform spectroscopy experiments. The nuclei of interest are produced by multinucleon transfer reactions, which have been recently attracting renewed interest as they provide a way to access neutron-rich nuclei that are difficult to produce by other methods such as complete fusion or fragmentation. We have performed nuclear and laser spectroscopy, lifetime and mass measurements of neutron-rich nuclei of refractory elements near the N = 126 region using 198,natPt, natTa, natW, and natIr targets irradiated with 136Xe beams. We also extend our spectroscopic studies into the neutron-rich actinide region using 238U beams. This paper introduces the KISS facility and provides an overview of the nuclear spectroscopy experiments carried out there. We also introduce the KISS-1.5 project, which was started in FY2024 to further extend the research into the neutron-rich region.

Monolayer vermiculite membranes for efficient hydrogen isotope separation.

H/D isotope separation faces critical challenges in terms of separation efficiency and cost. This study presents a novel, scalable fabrication of centimeter-scale, defect-free vermiculite monolayer membranes via a modified Langmuir-Blodgett method. These membranes demonstrate H/D separation efficiency comparable to monolayer graphene, promising cost-effective applications.

Development of a blue-violet high-power single-frequency diode laser system for 48Ca isotope separation

Development of a blue-violet high-power single-frequency diode laser system for ⁴⁸Ca isotope separation

The SPES target ion source automated storage system

At the SPES (Selective Production of Exotic Species) facility, intense Radioactive Ion Beams (RIBs) are produced by the interaction of a 40 MeV proton beam with a multi-foil uranium carbide target employing the Isotope Separation On-Line (ISOL) technique. The Target Ion Source (TIS) unit constitutes the core of the isotope production process. TIS units are replaced on a periodic basis during operation to maintain high performance. An automated storage system has been designed to accept highly radioactive TIS units and house them during a cooling period prior to decommissioning. The system is conceived to meet strict functional and safety requirements. Its peculiar design allows for improved reliability and availability during critical operations, as well as minimization of staff exposure to ionizing radiation during maintenance tasks. This contribution describes the design and control architecture of the Temporary Storage System (TSS). The equipment is part of a structured framework of remote manipulation, consisting of various machines interlocked with the Access Control System (ACS) and the Machine Protection System (MPS).

Additively manufactured tantalum cathode for FEBIAD type ion sources: production, geometric measurements, and high temperature test

The Laser Powder Bed Fusion (LPBF) is an Additive Manufacturing (AM) technology suitable to produce almost free-form metallic components. At Legnaro National Laboratories (LNL) of the Italian National Institute for Nuclear Physics (INFN), the LPBF process was recently used to produce parts of the Forced Electron Beam Induced Arc Discharge (FEBIAD) ion source for the SPES Isotope Separation On-Line (ISOL) facility. In this work are presented the feasibility assessment and production steps of tantalum cathodes produced via AM; in addition, the results concerning both the dimensional-geometrical measurements and the preliminary high-temperature test are reported.

Efficient hydrogen isotope separation utilizing photocatalytic capability

An N–O–C3N4 catalyst for catalytic hydrogen isotope separation.

The influence of crystal chemistry on lithium isotopic fractionation in pegmatite minerals

The understanding of lithium (Li) isotopic fractionation controlled by mineral species, especially those containing trace or minor amounts of Li (e.g., a few to tens of ppm), is hindered by lack of knowledge about the crystal chemistry of Li-bearing minerals. In this study, we performed solid-state Nuclear Magnetic Resonance (NMR) experiments, employing the Li7 Magic Angle Spinning (MAS) to investigate the local coordination environments of Li in minerals and their impact on Li isotopic fractionation. Our investigation focused on four coexisting minerals sourced from the Koktokay No. 3 pegmatite dike in the Xinjiang, China, namely quartz, K-feldspar, muscovite, and tourmaline, which has Li content and δLi7 value of 14.6 ppm and 3.90‰, 19.3 ppm and 7.09‰, 430 ppm and − 14.2‰, and 108 ppm and 13.42‰, respectively. Muscovite displayed the lowest δLi7 value, whereas tourmaline exhibited the highest value, and a considerable variation of 27.62‰ in δLi7 value was observed between muscovite and tourmaline. The analysis of Li7 MAS-NMR spectra further revealed distinct Li coordination environments among these minerals. A notable counterintuitive negative correlation exists between the δLi7 value and the chemical shift for the four Li-bearing minerals. This negative correlation contrasts to the expected Li isotopic fractionation under equilibrium conditions, in which enrichment of heavy Li isotopes is accompanied with large chemical shifts in Li-bearing minerals. This unexpected observation can be potentially attributed to nonequilibrium conditions of crystallization of the investigated minerals, coupled with fast diffusion of Li6 in minerals, boasting abnormally high coordination numbers due to weak LiO chemical bonds. Essentially, our study suggests that Li isotopic fractionation among Li-bearing minerals in pegmatite can be significant and is intricately influenced by both crystal chemistry and chemical diffusion.

Values for the Digestibility of Pea Protein Isolate or Casein Amino Acids Determined using the Dual Isotope Method Are Not Similar to Those Derived with the Standard Ileal Balance Method in Healthy Volunteers

BackgroundThe measurement of ileal amino acid (AA) digestibility is invasive and inappropriate when applied to vulnerable populations. The dual isotope method has been developed over the past 5 y as an alternative method. ObjectiveThe aim of this work was to compare the indispensable amino acid (IAA) digestibility values of 2 different proteins obtained using the dual isotope and the standard ileal balance methods in the same subjects. MethodsFifteen healthy adults completed the study. Over 4 h, they ingested 9 successive portions of mashed potatoes containing the test protein (pea protein or casein) labeled intrinsically with 15N and 2H, and a 13C-free AA mixture as a reference for the dual isotope method. Plasma was sampled regularly over the 8-h postprandial period, whereas the ileal digesta was collected continuously via a naso-ileal tube. Isotopic enrichments (15N and 13C) were measured in the digesta for the direct determination of ileal IAA digestibility, whereas plasma enrichments (2H and 13C) were measured to determine IAA digestibility using the dual isotope method. ResultsThe 4-h repeated meal procedure enabled the almost complete digestion of test proteins at 8 h and the attainment of a plasma isotopic plateau between 2.5 and 4 h. These conditions were necessary to perform the ileal balance and dual isotope methods simultaneously. For pea protein, the mean IAA digestibility was similar between the 2 methods, but significant differences (from 10% to 20%) were observed for individual IAA values. For casein, IAA digestibility was significantly lower with the dual isotope method for all the IAA analyzed. ConclusionsUnder our experimental conditions, the degree of agreement between the dual isotope and ileal balance methods varied among AAs and depended on the protein source. Further research is needed to validate the dual isotope method.This study was registered at clinicaltrials.gov as NCT04072770.

Optimization of multicomponent isotopes separation cascades parameters using improved grey wolf optimizer algorithm

The number of variables and design parameters in the multicomponent isotope separation cascades is considerable, and it is highly challenging to choose the best arrangement by obtaining the minimum interstage flow rate. Therefore, it is very important to develop a computational tool with high capability for calculating the cascade optimal parameters. The Improved Grey Wolf Algorithm, IGWO, is used in this study to develop an efficient code called the Isotopic Separation Real Code (ISRC-IGWO), which calculates the optimum parameters in the cascade for the separation of multicomponent mixtures. Investigations have been conducted in 4 separate tests to demonstrate this code's capability for computing the parameters with values close to the optimal conditions (in convergence to the near-optimal cascade). These evaluations have been carried out for both square and taper cascades, and different objective functions have been included in all tests. The findings show that ISRC-IGWO results are in agreement with optimal parameters calculation using other existing methods and IGWO is able to calculate cascade optimal parameters.

Antimony isotopic fractionation during intensive chemical weathering of basalt in the tropics

This study explored the mechanism of antimony (Sb) isotopic fractionation during chemical weathering and soil biogeochemical processes, which have important implications for Sb isotopic composition in the hydrosphere. We analyzed the major and trace element contents and Sb isotopic composition along an 8 m deep basalt weathering profile in the Huguangyan area of Guangdong Province, southern China. Mineral adsorption experiments were conducted to determine the mechanism of Sb isotopic fractionation in the weathering profile. The following minerals, α-FeOOH, γ-Fe2O3, β-MnO2, γ-Al2O3, montmorillonite-K10, and kaolinite-1A, preferentially adsorbed light Sb isotopes, and increased pH may lead to a lighter isotopic composition of adsorbed Sb. The positive values of τSbTiO2 in the upper profile reflect exogenous Sb inputs, such as rainfall and litterfall. Accordingly, Sb isotopic fractionation is controlled by Sb adsorption onto organic matter and Fe (hydr)oxides in surface soil. At a depth of 1.8 m, Sb and other redox-sensitive elements, such as Fe, Mn, Ce, Co, Cr, and Mo, were distinctly enriched. Changes in the redox conditions result in strong Sb isotopic fractionation. In the middle layer (2–4 m), the combined effects of changes in organic matter content, soil pH, and weathering intensity explains the enrichment of light Sb isotopes. The bottom layer of the profile did not receive exogenous Sb and exhibited an Sb isotopic fractionation pattern similar to that of the basaltic bedrock. In the bottom layer, secondary Fe (hydr)oxides (e.g., goethite and hematite) preferentially adsorb the light Sb isotope (121Sb), whereas the heavy Sb isotope (123Sb) is released into the aquatic environment during intensive chemical weathering.

Deuterium Enrichment by PEM Water Electrolysis Using Water Circulation

Artemis Project, an international space exploration project proposed by the United States and involving Japan, plans a long-term manned lunar exploration in the late 2020s. That project considers the capture of He3, a resource for fusion that does not exist on Earth. On the other hand, He3 is produced by the half-life of tritium (T). Now new hydrogen isotope separation is required for recovering T exhausted from nuclear reactors.The water electrolysis is well known to enrich protium (H) in gas phase and, deuterium (D) and T in the electrolyte [1]. The modern electrolysis is performed by solid polymer membrane water electrolysis (PEMWE). However, there are few reported cases for the isotope separation by PEMWE. In this study for pursing high D separation, the optimization of the electrolysis system was investigated.The initial D concentrations in the electrolyte were 10, 30, and 50 at% IrO2 was used as the anode catalyst and Pt/C as the cathode one. The electrolysis was galvanostatically conducted. Hydrogen gas was analyzed by a quadrupole mass spectrometer (Q-Mass) to determine the ratio of H2, HD, and D2. The electrolyte was analyzed by Fourier transform infrared spectrophotometer (FT-IR) to determine the ratio of H2O, HDO, and D2O.Figure. 1 shows the schematic illustration of gas and water flow chart in experimental setup. Electrolyte was sent to the cell by the electric pump constantly. When the experiment was carried out, evolved gas and drained water was analyzed. The water out from the cell was returned into the electrolyte tank and electrolyzed repeatedly. The gas was introduced to Q-Mass. By using this circulation system, D was concentrated in the electrolyte efficiently . In this experiment, its concentration reached about 95at.%. To quantitatively evaluate the D enrichment by PEMWE, the separation factor α was calculated from the ratio of D concentrations in the electrolyte to the gas. The value of α was approximately 4.0. However, the valueslightly decreased above 90 at.% D. More detailed results will also be presented in our Poster, #176411. Figure 1