Electromigration Separation of Lithium Isotopes: The Effect of Electrode Solutions

Both lithium-6 and lithium-7 with high abundance are indispensable materials in nuclear industry. Here, an aqueous solution│organic solution│aqueous solution system was fabricated to separate lithium isotopes. The effects of species and concentration of electrolytes in the electrode solutions on the lithium ions migration and lithium isotope separation with different voltages and migration time was studied. It was found that lithium-7 was enriched in aqueous solutions on both sides at 0 V and 2 V, while lithium-7 was enriched in anode solution and lithium-6 was enriched in cathode solution at 16 V. The weakening stability of the chelate consisted of crown ether and lithium ion with increasing voltage was believed to the possible reason. Meanwhile, the variation of electrolyte in electrode solution led to notable changes in migration ratio of lithium ions and lithium isotope separation effect, which can be attributed to the different degree of both ionization and hydrolysis for various electrolytes in aqueous solutions and the different ability of H+ and NH4+ to replace Li+ of chelate in organic solutions. This work is of great significance for the selection of electrode solutions in electromigration separation of lithium isotopes and even other electrochemical systems.

Numerical Studies of Atomic Three-Step Photoionization Processes with Non-Monochromatic Laser Fields

The atomic selective multi-step photoionization process is a critical step in laser isotope separation. In this article, we have studied three-step photoionization processes with non-monochromatic laser fields theoretically based on the semi-classical theory. Firstly, three bandwidth models, including the chaotic field model, de-correlation model and phase diffusion model, are introduced into the density matrix equations. The numerical results are made comparisons comprehensively. The phase diffusion model is selected for further simulations in terms of the correspondence degree to physical practice. Subsequently, numerical calculations are carried out to identify the influences of systematic parameters, including laser parameters (Rabi frequencies, bandwidths, relative time delays, frequency detunings) and atomic Doppler broadening, on photoionization processes. In order to determine the optimum match between different systematic parameters, ionization yield of resonant isotope and selectivity factor are adopted as evaluation indexes to guide the design and optimization process. The results in this work can provide a rewarding reference for laser isotope separation.

Helium isotope separation by bi-layer membranes of g-C3N4

The problem of helium isotope separation via bi-layer membranes of graphitic carbon nitride g-C3N4 has been studied. The probability of passing isotopes through the membrane is derived from solving the Schrödinger integral equation using Hermite polynomials. The potential energy of the membrane is calculated based on modified Lennard-Johnes potential. The separation degree of the 3He/4He reaches the value of 1045 due to the resonant effect.

Preliminary Study on Minor Actinide Incineration in RSG-GAS without Isotope Separation

Minor actinides (MA) resulted from nuclear power plants is often considered as nuisance in spent fuel management due to its considerably long half-life. One of available strategies to deal with MA is to incinerate it, in order to reduce its radioactivity. This paper presents a study on MA incineration in RSG-GAS research reactor. Unlike previous study, this work did not separate the MA into individual isotopes, but incinerated as a whole. ORIGEN2.1 code is employed to calculate MA incineration within RSG-GAS core. MA composition used in this study consists of Np, Am, and Cm isotopes. The Central Irradiation Position (CIP) of RSG-GAS is loaded by 6 kg of MA and irradiated for two years. The result shows that about 1 kg of MA were incinerated after two years of irradiation, or 18,87% of the initial concentration. However, the increase of Cm-242 isotope, along with newly-formed Pu isotopes, were found to be significantly increasing short-term radioactivity compared to un-irradiated MA. Thus, two years-worth of MA incineration cannot be considered as effective, and other strategies must be pursued.

Graphene-based composite membranes for isotope separation: challenges and opportunities

Graphene-based membranes have got significant attention in wastewater treatment, desalination, gas separation, pervaporation, fuel cell, energy storage applications due to their supreme properties. Recently, studies have confirmed that graphene based membranes can also use for separation of isotope due to their ideal thickness, large surface area, good affinity, 2D structure etc. Herein, we review the latest groundbreaking progresses in both theoretically and experimentally chemical science and engineering of both nanoporous and lamellar graphene-based membrane for separation of different isotopes. Especially focus will be given on the current issues, engineering hurdles, and limitations of membranes designed for isotope separation. Finally, we offer our experiences on how to overcome these issues, and present an ideas for future improvement and research directions. We hope, this article is provide a timely knowledge and information to scientific communities, and those who are already working in this direction.

CALCULATION PROGRAM FOR THE PROCESSING OF LOW-CONCENTRATED TRITIUM AND DEUTERIUM WASTE THROUGH THE CECE ISOTOPIC SEPARATION PROCESS

Within the research conducted at our Institute of Cryogenic and Isotopic Technologies (ICSI), is developed a project entitled "Innovative CECE process solution to promote a new technology for decontamination of liquid waste, tritium low concentrated and deuterium recovery”. The main objective of the project carried out within our team is to promote an innovative solution of CECE isotopic separation process (Combined Electrolysis and Catalytic Exchange), part of a new technology for decontamination of liquid waste, poorly concentrated in tritium, generated by nuclear reactors, ensuring increased recovery of the isotope deuterium and tritium. This paper presents the current stage of an innovative CECE isotopic separation process solution, and also the mathematical model developed for the simulation of hydrogen isotope separation processes through the CECE process and a theoretical analysis based on numerical data resulting from the simulation of two CECE plant operating mode.

Advanced Laser-Photoionization Scheme of Separation of Heavy Isotopes in the Gases Separator Devices

An effective approach to determining the parameters of the optimal schemes of the method of laser selective photoionization of atoms (elements and isotopes) with finite ionization due to collisions, ionization by a pulsed electric field, ionization through high (Rydberg) states and narrow autoionization resonances for the separation of heavy isotopes has been proposed. in gas separator devices. On the basis of the theory of optimal control and previously developed quantum models for calculating the characteristics of elementary atomic processes, optimization models of isotope separation are numerically implemented in the scheme of selective laser photoionization with ionization due to collisions in gas mixtures, ionization by a pulsed electric field, autoionization, etc. etc. The data obtained quantitatively confirm the promise of the method of laser photoionization with finite ionization due to collisions, ionization by a pulsed electric field, ionization through high-lying (Rydberg) states and narrow autoionization resonances and give a set of parameters for the desired optimal schemes, in particular, the laser pulse optimal shape for rubidium and uranium isotopes.