Process intensification of element extraction using centrifugal contactors in the nuclear fuel cycle

This review focuses on consolidating solvent extraction performed in the process intensification equipment known as Centrifugal Contactors (CCs), implemented in Spent Nuclear Fuel (SNF) reprocessing and radioactive waste processing. Recovery of valuable actinides is important from sustainability perspectives as it is a source of metals of technological interest from SNF, specifically the recovery of fissile and fertile material, and can also be employed in the processing of Waste Electrical and Electronic Equipment (WEEE). Solvent extraction (also referred to as liquid–liquid extraction, or aqueous separation), is employed in the separation of f-block elements and fission products in SNF. The sequential isolation using different flowsheets has been performed on a range of scales using CCs. However, solids, either present in the feed solution or formed in situ, are always cited as a concern for the operability of CCs, and their extraction efficiencies. This review quantifies the unexpected solid arisings and accumulation during operation in the presence and absence of highly radioactive isotopes from bench to plant scale. The review concludes with techniques implemented for the removal of solids from CCs

Characterization of large tilt-angle flexoelectro-optic switching in chiral nematic liquid crystal devices

The “flexoelastic ratio”, which is the ratio of the effective flexoelectric coefficient to the elasticcoefficients, is commonly used to characterize the electro-optic behavior of chiral nematic liquid crystal(LC) devices that exhibit flexoelectro-optic switching. In the uniform lying helix configuration, thiselectro-optic effect is manifested as a rapid (~100 s) rotation of the macroscopic optic axis when anelectric field is applied perpendicular to the helix axis of the chiral nematic LC and is attractive for bothintensity and phase modulation devices. There has been renewed interest in this electro-effect as newLC materials and mixtures have been developed that exhibit large tilt angles, , of the optic axis ( ≥45°) whilst maintaining a fast response time. In this Letter, we consider the relevance of the flexoelasticratio when characterizing the performance of the devices and find that an alternative ratio is required tocharacterize materials that can switch by = ±45° when the pitch is constrained. We show that for largetilt angles of the optic axis the values for the new and conventional flexoelastic ratios measurablydiverge. In addition, a simple way of determining this new characteristic ratio is presented that involvesdetermining the electric field amplitude at the point the transmission levels are the same for bothpositive and negative electric field polarities

Single-mode sapphire fiber Bragg grating

We present here the inscription of single-mode waveguides with Bragg gratings in sapphire. The waveguide Bragg gratings have a novel multi-layer depressed cladding design in the 1550 nm telecommunications waveband. The Bragg gratings have a narrow bandwidth (<0.5 nm) and have survived annealing at 1000{\deg}C. The structures are inscribed with femtosecond laser direct writing, using adaptive beam shaping with a non-immersion objective. A single-mode sapphire fiber Bragg grating is created by writing a waveguide with a Bragg grating within a 425 {\mu}m diameter sapphire optical fiber, providing significant potential for accurate remote sensing in ultra-extreme environments.Comment: Submitted to Optica 12 November 202

On-chip beam rotators, polarizers and adiabatic mode converters through low-loss waveguides with variable cross-sections

Photonics integrated circuitry would benefit considerably from the ability to arbitrarily control waveguide cross-sections with high precision and low loss, in order to provide more degrees of freedom in manipulating propagating light. Here, we report on a new optical-fibres-compatible glass waveguide by femtosecond laser writing, namely spherical phase induced multi-core waveguide (SPIM-WG), which addresses this challenging task with three dimensional on-chip light control. Precise deformation of cross-sections is achievable along the waveguide, with shapes and sizes finely controllable of high resolution in both horizontal and vertical transversal directions. We observed that these waveguides have high refractive index contrast of 0.017, low propagation loss of 0.14 dB/cm, and very low coupling loss of 0.19 dB coupled from a single mode fibre. SPIM-WG devices were easily fabricated that were able to perform on-chip beam rotation through varying angles, or manipulate polarization state of propagating light for target wavelengths. We also demonstrated SPIM-WG mode converters that provide arbitrary adiabatic mode conversion with high efficiency between symmetric and asymmetric non-uniform modes; examples include circular, elliptical modes and asymmetric modes from ppKTP waveguides which are generally applied in frequency conversion and quantum light sources. Created inside optical glass, these waveguides and devices have the capability to operate across ultra-broad bands from visible to infrared wavelengths. The compatibility with optical fibre also paves the way toward packaged photonic integrated circuitry, which usually needs input and output fibre connections

Predicting mass transfer in liquid–liquid extraction columns

In this work, the GEneralised Multifluid Modelling Approach (GEMMA) is applied to the simulation of liquid–liquid extraction in a Rotating Disc Column (RDC) and a Pulsed Sieve-plate Extraction Column (PSEC). A mass transfer modelling methodology is developed, in which the multiphase flows, droplet size distribution and dispersed phase holdup predicted with computational fluid dynamics are coupled to mass transfer correlations to predict the overall mass transfer. The numerical results for the stage-averaged dispersed phase holdup, Sauter mean droplet diameter and axial solute concentration in the RDC and PSEC agree with experimental observations. The proposed modelling method provides an accurate predictive tool for complex multiphase flows, such as those observed in intensified liquid–liquid extraction, and provides an alternative approach to column design using empirical correlations or pilot plant study

Topologically controlled multiskyrmions in photonic gradient-index lenses

Skyrmions are topologically protected quasiparticles, originally studied in condensed-matter systems and recently in photonics, with great potential in ultra-high-capacity information storage. Despite the recent attention, most optical solutions require complex and expensive systems yet produce limited topologies. Here we demonstrate an extended family of quasiparticles beyond normal skyrmions, which are controlled in confined photonic gradient-index media, extending to higher-order members such as multiskyrmions and multimerons, with increasingly complex topologies. We introduce new topological numbers to describe these complex photonic quasiparticles and propose how this new zoology of particles could be used in future high-capacity information transfer. Our compact creation system lends integrated and programmable solutions of complex particle textures, with potential impacts on both photonic and condensed-matter systems for revolutionizing topological informatics and logic devices

High-precision optical fiber sensing beyond 1000{\deg}C

Sapphire fiber can withstand around 2000{\deg}C, but it is multimoded, giving poor precision sensors. We demonstrate a single-mode sapphire fiber Bragg grating temperature sensor operating up to 1200{\deg}C. The repeatability above 1000{\deg}C is within {\pm}0.08%.Comment: 4 Pages, 5 Figure

On-chip beam rotators, polarizers and adiabatic mode converters through low-loss waveguides with variable cross-sections

Photonics integrated circuitry would benefit considerably from the ability to arbitrarily control waveguide cross-sections with high precision and low loss, in order to provide more degrees of freedom in manipulating propagating light. Here, we report on a new optical-fibres-compatible glass waveguide by femtosecond laser writing, namely spherical phase induced multi-core waveguide (SPIM-WG), which addresses this challenging task with three dimensional on-chip light control. Precise deformation of cross-sections is achievable along the waveguide, with shapes and sizes finely controllable of high resolution in both horizontal and vertical transversal directions. We observed that these waveguides have high refractive index contrast of 0.017, low propagation loss of 0.14 dB/cm, and very low coupling loss of 0.19 dB coupled from a single mode fibre. SPIM-WG devices were easily fabricated that were able to perform on-chip beam rotation through varying angles, or manipulate polarization state of propagating light for target wavelengths. We also demonstrated SPIM-WG mode converters that provide arbitrary adiabatic mode conversion with high efficiency between symmetric and asymmetric non-uniform modes; examples include circular, elliptical modes and asymmetric modes from ppKTP waveguides which are generally applied in frequency conversion and quantum light sources. Created inside optical glass, these waveguides and devices have the capability to operate across ultra-broad bands from visible to infrared wavelengths. The compatibility with optical fibre also paves the way toward packaged photonic integrated circuitry, which usually needs input and output fibre connections

Characterising the dispersed phase hydrodynamics in Pulsed Sieve-plate Extraction Columns

This work uses a pilot-scale Pulsed Sieve-plate Extraction Column (PSEC) to characterise the dispersed phase hydrodynamics and generate a dataset suitable for validating Computational Fluid Dynamics (CFD) models. The column was operated over different throughputs, pulse amplitudes and plate designs to characterise the operational envelope, and stage-wise measurements were made for droplet size distribution and rise velocity