Reprocessing of spent nuclear fuel (SNF) is an important task in a frame of ecology and rational use of natural resources. Uranium, as the main component of SNF (>95%), can be recovered for further ...use as fresh nuclear fuel. To minimize an amount of solid radioactive waste generated during SNF reprocessing, new extractants are under investigation. Diamides of 1,10-phenanthroline-2,9-dicarboxylic acid are perspective tetradentate N-donor ligands that form strong complexes with f-elements, which are soluble in polar organic solvents. As an example of three ligands of this class, we conducted a comparative study and showed how the substituent in the amide functional group affects the extraction ability toward uranyl nitrate from nitric acid media. We have performed a careful study (NMR, FT-IR, XRD, RMC-EXAFS) of the structures of synthesized complexes of new ligands with uranyl nitrate and used quantum mechanical calculations to explain the discovered regularities through.
In this work we report on new examples of phenanthrolindiamides containing asymmetric centers in amide substituents. The synthesized ligands are expected to have complex thermodynamic behavior. Their ...structure was unambiguously confirmed by a combination of spectral analysis methods and X-ray analysis. It is shown that the obtained ligands form complexes with nitrates of rare-earth elements, and the stability constants of such complexes in acetonitrile solution were also measured. The performed solvent extraction tests revealed a significant effect of methyl groups in cyclic amide substituents on the distribution ratios and selectivity factors in the lanthanides(
iii
) and Am(
iii
) series in comparison with the previously studied ligands based on unsubstituted pyrrolidine. The observed effects are explained from the standpoint of quantum chemistry calculations taking into account possible stereoisomerism.
In this work we report on new examples of phenanthrolindiamides containing asymmetric centers in amide substituents.
The diagnostic of the peripheral plasma parameters in terms of the relation of lines of neutral helium is included in the diagnostic complex of the tokamak Globus-M2. The first measurements of the ...peripheral plasma parameters are performed near the lower X point. The measured spatial distributions of the electron temperature and density are in satisfactory agreement with the simulation with the SOLPS-ITER code.
The effect of irradiation by 30‐keV Ga+ and 35‐keV He+ ions (in relatively small doses) on the excitonic reflectivity spectra of single InGaAs/GaAs quantum‐well structures is studied. It is found ...that the irradiation results in decreasing intensity and broadening of the excitonic resonances in the reflectivity spectra for all the doses. It is shown that these changes are not related to a decrease of the exciton transition oscillator strength and, therefore, to the irradiation‐induced destruction of the excitonic states, but can be rather ascribed to a common cause, namely, to inhomogeneous broadening of the excitonic resonances proportional to the exposure dose. A tentative model of the irradiation‐induced broadening is considered, with the mechanism of the process being a consequence of scattering of the 2D excitons by structural defects associated with Ga(In) and As vacancies arising upon collisions of the high‐energy ions with regular atoms of the crystal structure. The model is used to compare experimental dependence of efficiency of the Ga+‐ion‐induced broadening on distance of the quantum well from the irradiated surface with a similar dependence calculated using the Monte‐Carlo technique. A discrepancy between the results of simulation and experimental data is discussed.
Among the peripheral instabilities observed at the Globus-M2 tokamak, two types of edge localized modes (ELMs) are brought into focus: ELMs synchronized and desynchronized with the sawtooth ...oscillations. The desynchronized ELMs appear in regimes that are characterized by high values of pressure in the pedestal,
p
ped
≥ 3 kPa, and they are observed in discharges with the toroidal magnetic field
B
T
> 0.6 T and plasma current
I
P
> 0.3 MA. The desynchronized ELMs belong to the type-III/V with the dominating effect of the peeling mode. The synchronized ELMs were observed in a wider range of discharge parameters, including at
B
T
< 0.6 T and
I
P
< 0.3 MA. Calculations of the stability of the peeling-ballooning (PB) mode showed that at pedestal width ψ
norm
= 0.09 and
p
ped
> 3.5 kPa, destabilization of PB modes is possible without additional influence. Experimental data shows that the microtearing mode plays a dominant role in the pedestal. The microtearing mode does not allow the pedestal at Globus-M2 tokamak to reach the state of the unstable kinetic ballooning mode (KBM), which explains the low predictive power of the EPED model at this tokamak.
The results of measuring the electron temperature and density spatial distributions in plasma of the Globus-M2 tokamak using the Thomson scattering diagnostics are presented. The diagnostics provides ...measurements throughout the entire tokamak discharge, starting from time of gas breakdown. The Thomson scattering data were analyzed in order to determine the positions of the last closed flux surface, the plasma magnetic axis, and the radius of inversion during the saw-tooth oscillations. The results of measurements performed during the internal reconnection of magnetic field lines are presents, as well as the dynamics of spatial distributions of electron temperature, density and pressure during the plasma transition to the H-mode. The results of measuring the electron temperature distribution in the scrape-off layer using the Thomson scattering diagnostics are also presented for distances up to 4 cm outside the last closed flux surface.
This paper discusses the technology of formation of photoresistive structures based on a composite of lead selenide and lead selenite. The structures are formed by the oxidation of
n
-PbSe ...polycrystalline films. Film The surface modification mechanism of
n
-PbSe films in the oxidation process is analyzed by a Zeiss Merlin scanning electron microscope (SEM). The new results of the authors on the oxidation mechanism of
n
-PbSe, together with their earlier publications, are summarized and their consistency with each other is examined. A theoretical model (hypothesis) of the potential profile of a photosensitive heterojunction is proposed, in which each crystal of the
n
-PbSe film during oxidation in an atmosphere of dry air forms a continuous shell on the
p
-PbSeO
3
surface. The hypothesis on the structural model of the photosensitive heterojunction proposed by other authors, which is based on the oxidation mechanism proposed by us, is practically confirmed in this study.
Abstract
The work presents the results of the energy confinement study carried out on the compact spherical tokamak Globus-M2 with a toroidal magnetic field as high as 0.8 T. A reproducible and ...stable discharge was obtained with the average plasma density (5–10) × 10
19
m
−3
. Despite the increase in the magnetic field, the neutral beam injection (NBI) led to clear and reproducible transition to the H-mode accompanied by a decrease in the turbulence level at the plasma edge. NBI allowed effectively heat the plasma: electron and ion temperatures in the plasma core exceeded 1 keV. Compared to the previous experiments carried out with a toroidal magnetic field as high as 0.4 T plasma total stored energy was increased by a factor of 4. The main reason or this phenomenon is a strong dependence of the energy confinement time on the toroidal magnetic field in the spherical tokamak. It was experimentally confirmed that such kind of dependence is valid for ST with magnetic field up to 0.8 T. It has also been shown that the enhancement of the energy confinement in Globus-M2 with collisionality decrease is associated with an improvement of both electron and ion thermal insulation.
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