Mathematical modelling of intensified extraction for spent nuclear fuel reprocessing

Small scale extractors seem to be a promising intensified alternative to the conventional solvent extraction technologies, because of the well described hydrodynamics, enhanced mass transfer, and good phase separation at the end. One of the most interesting applications of intensified extractions is the reprocessing of spent nuclear fuel. Operating in small channels can reduce the volumes of involved hazardous materials and the residence times, thus minimising the degradation of the solvent and its regeneration cost. Finally, nuclear criticality safety may be easily achieved. In this paper, the application of small channels on spent nuclear fuel reprocessing has been investigated. A mathematical model of a multi-component liquid-liquid extraction has been developed. The multi-component system consists of U, Pu, HNO 3 , HNO 2 , Zr, Ru, Tc, Np(IV), Np(V) and Np(VI), the organic solvent is a mixture of 30% (v/v) Tri-Butyl Phosphate (TBP) and a paraffinic diluent. A segmented flow pattern, with the aqueous phase dispersed in a continuous organic phase, has been assumed. Calculations for the estimation of mass transfer, redox reactions, pressure drop, nuclear criticality and TBP hydrolysis have been included in the model. To increase the flow rates, the number of small channels was increased (scale out) and a comb-like manifold was considered to ensure good flow distribution in each channel. The problem is formulated as a mixed integer nonlinear programming problem and is implemented in the General Algebraic Modeling System (GAMS). The results show that this alternative technology for liquid-liquid extraction offers advantages, especially in terms of solvent degradation and low holdup volume

Process intensification applied to spent nuclear fuel reprocessing: An alternative flowsheet using small channels

Commercial plants for spent nuclear fuel reprocessing rely on the Plutonium Uranium Extraction (PUREX) process, based on traditional liquid–liquid extraction technologies. In this paper, an alternative flowsheet for spent nuclear fuel reprocessing is proposed, based on small-scale extractors to overcome some of the issues related to the conventional technologies, such as solvent degradation, size and nuclear criticality control. The main goal of the process is to preclude the risk of nuclear proliferation, hence a mixed uranium/plutonium oxide is produced instead of pure plutonium. A superstructure optimisation based framework has been used to identify a process with several benefits over the conventional process. Novel flow configurations and organic solvent composition have been investigated. A large number of components and chemical reactions are included in the framework. The resulting model is a mixed integer nonlinear optimisation problem, implemented in the General Algebraic Modeling System (GAMS). The most promising flowsheet identified is more cost effective than the conventional one. Furthermore, advantages in terms of safety and separation efficiency have been achieved. It was found that increasing the inner diameter of the small channels up to 2.5 mm, as well as increasing the tributyl phosphate fraction in the organic solvent, are advantageous

Experimental and CFD scale-up studies for intensified actinide/ lanthanide separations

In this paper, systematic studies are performed to identify the parameters that influence the selective separation of actinides from a mixture with lanthanides in small channels. In particular, the separation of dioxouranium metal ions (UO2+2) from a binary U(VI)/Er(III) mixture in a nitric acid solution by an organic TBP/kerosene (Exxsol D80) phase, relevant to spent nuclear fuel reprocessing is investigated. The effects of parameters such as TBP concentration, organic-to-aqueous phase flow rate ratio, channel size, and residence time on mass transfer are evaluated, whilst the mass transfer performance in the extraction channels is further analysed using two important hydrodynamic features, i.e. plug formation time and interfacial area to volume ratio. Circular channels with diameters from 1 to 3 mm are used to investigate the effect of scale on the mass transfer characteristics. The importance of the mixing zone on mass transfer is also evaluated. A CFD model is proposed to simulate the mass transfer during plug flow. Using only one experimental point, once the plug has been formed, the model is able to predict extraction percentage with less than 4% difference compared to the experiments

Conditions driving chemical freeze-out

We propose the entropy density as the thermodynamic condition driving best the chemical freeze-out in heavy-ion collisions. Taking its value from lattice calculations at zero chemical potential, we find that it is excellent in reproducing the experimentally estimated freeze-out parameters. The two characteristic endpoints in the freeze-out diagram are reproduced as well.Comment: 8 pages, 5 eps figure

Hydrodynamics and mass transfer in segmented flow small channel contactors for uranium extraction

In this work, the extraction of U(VI) by tributyl phosphate (TBP) is studied in small channels of different sizes, operated in segmented flow. The variables analysed include the channel diameter (1–4 mm I.D.), mixture velocity (1.06 - 4.24 cm s−1), volume fraction of the continuous phase (between 0.200 and 0.500), and concentration of extractant (TBP 30% v/v in kerosene and TBP 100%). The hydrodynamic characteristics of the flow, such as plug and slug lengths, specific interfacial area, and dispersed phase holdup, were obtained experimentally using high-speed imaging, while the pressure drop was measured with a differential pressure transducer. These parameters were correlated to the studied variables. The concentration of uranium in the aqueous phase was measured with UV-vis spectroscopy, and the mass transfer coefficients were compared with the predictions of a numerical model of segmented flow developed in Comsol Multiphysics, with good agreement

Electromagnetic field evolution in relativistic heavy-ion collisions

The hadron string dynamics (HSD) model is generalized to include the creation and evolution of retarded electromagnetic fields as well as the influence of the magnetic and electric fields on the quasiparticle propagation. The time-space structure of the fields is analyzed in detail for non-central Au+Au collisions at $\sqrt{s_{NN}}=$200 GeV. It is shown that the created magnetic field is highly inhomogeneous but in the central region of the overlapping nuclei it changes relatively weakly in the transverse direction. For the impact parameter $b=$10 fm the maximal magnetic field - perpendicularly to the reaction plane - is obtained of order $eB_y/m_\pi^2\sim$5 for a very short time $\sim$ 0.2 fm/c, which roughly corresponds to the time of a maximal overlap of the colliding nuclei. We find that at any time the location of the maximum in the $eB_y$ distribution correlates with that of the energy density of the created particles. In contrast, the electric field distribution, being also highly inhomogeneous, has a minimum in the center of the overlap region. Furthermore, the field characteristics are presented as a function of the collision energy and the centrality of the collisions. To explore the effect of the back reaction of the fields on hadronic observables a comparison of HSD results with and without fields is exemplified. Our actual calculations show no noticeable influence of the electromagnetic fields - created in heavy-ion collisions - on the effect of the electric charge separation with respect to the reaction plane.Comment: 17 pages, 22 figures, title changed by editor, accepted for PR

Design optimization of microfluidic-based solvent extraction systems for radionuclides detection

The development of reliable and fast automated methodologies to detect and identify radionuclides during the decommissioning of nuclear power plants is of paramount importance. In this regard, process flowsheeting and computational simulations are useful tools to aid the design and testing of these advanced detection technologies. We implement an optimization based design procedure for the design of continuous analysis systems based on microfluidic solvent extraction and on-line measurement to detect radionuclides in nuclear waste. The optimization of such detection systems is treated as a design under uncertainty problem. The systems are based on thermal lens microscopy as the detection instrument. We demonstrate our approach on a flowsheet for the detection of trivalent lanthanides in organic and aqueous solutions. We highlight the importance of using computer-aided optimization based procedures to design microsystems comprising several chemical operations and their coupling with the detection step. It constitutes a proof of concept and a first step towards robust optimization based modelling approaches for the design of microfluidic lab-on-a-chip platforms for the detection of radionuclides in nuclear waste

Mist and Edge Computing Cyber-Physical Human-Centered Systems for Industry 5.0: A Cost-Effective IoT Thermal Imaging Safety System

While many companies worldwide are still striving to adjust to Industry 4.0 principles, the transition to Industry 5.0 is already underway. Under such a paradigm, Cyber-Physical Human-centered Systems (CPHSs) have emerged to leverage operator capabilities in order to meet the goals of complex manufacturing systems towards human-centricity, resilience and sustainability. This article first describes the essential concepts for the development of Industry 5.0 CPHSs and then analyzes the latest CPHSs, identifying their main design requirements and key implementation components. Moreover, the major challenges for the development of such CPHSs are outlined. Next, to illustrate the previously described concepts, a real-world Industry 5.0 CPHS is presented. Such a CPHS enables increased operator safety and operation tracking in manufacturing processes that rely on collaborative robots and heavy machinery. Specifically, the proposed use case consists of a workshop where a smarter use of resources is required, and human proximity detection determines when machinery should be working or not in order to avoid incidents or accidents involving such machinery. The proposed CPHS makes use of a hybrid edge computing architecture with smart mist computing nodes that processes thermal images and reacts to prevent industrial safety issues. The performed experiments show that, in the selected real-world scenario, the developed CPHS algorithms are able to detect human presence with low-power devices (with a Raspberry Pi 3B) in a fast and accurate way (in less than 10 ms with a 97.04% accuracy), thus being an effective solution that can be integrated into many Industry 5.0 applications. Finally, this article provides specific guidelines that will help future developers and managers to overcome the challenges that will arise when deploying the next generation of CPHSs for smart and sustainable manufacturing.Comment: 32 page

An orally active formulation of angiotensin-(1-7) produces an antithrombotic effect

INTRODUCTION AND OBJECTIVE: The heptapeptide angiotensin-(1-7) is a component of the renin-angiotensin system, which promotes many beneficial cardiovascular effects, including antithrombotic activity. We have recently shown that the antithrombotic effect of angiotensin-(1-7) involves receptor Mas-mediated NO-release from platelets. Here, we describe an orally active formulation based on angiotensin-(1-7) inclusion in cyclodextrin [Ang-(1-7)- CyD] as an antithrombotic agent. Cyclodextrins are pharmaceutical tools that are used to enhance drug stability, absorption across biological barriers and gastric protection. METHOD: To test the antithrombotic effect of Ang-(1-7)-CyD, thrombus formation was induced in the abdominal vena cava of spontaneously hypertensive rats that were pretreated either acutely or chronically with Ang-(1-7)-CyD. Male Mas-knockout and wild-type mice were used to verify the role of the Mas receptor on the effect of Ang-(1-7)-CyD. RESULTS: Acute or chronic oral treatment with Ang-(1-7)-CyD promoted an antithrombotic effect (measured by thrombus weight; all values are, respectively, untreated vs. treated animals) in spontaneously hypertensive rats (acute: 2.86 + 0.43 mg vs. 1.14 + 0.40 mg; chronic: 4.27 + 1.03 mg vs. 1.39 + 0.68 mg). This effect was abolished in Mas-knockout mice (thrombus weight in Mas wild-type: 0.76 + 0.10 mg vs. 0.37 + 0.02 mg; thrombus weight in Mas-knockout: 0.96 + 0.11 mg vs. 0.87 + 0.14 mg). Furthermore, the antithrombotic effect of Ang-(1-7)-CyD was associated with an increase in the plasma level of Angiotensin-(1-7). CONCLUSION: These results show for the first time that the oral formulation Ang-(1-7)-CyD has biological activity and produces a Mas-dependent antithrombotic effect

From QCD lattice calculations to the equation of state of quark matter

We describe two-flavor QCD lattice data for the pressure at finite temperature and zero chemical potential within a quasiparticle model. Relying only on thermodynamic selfconsistency, the model is extended to nonzero chemical potential. The results agree with lattice calculations in the region of small chemical potential.Comment: 5 eps figure