Electron Backscattered Diffraction for the Study of Matrices for Immobilization of Actinides Composed of the Murataite-Type Phases

Crystallography Reports - Electron backscattered diffraction (EBSD) has been used to analyze structures of natural minerals and artificial compounds for almost three decades. In recent years, it is...     

Synthesis and phase relations in the system with garnet-type composition: [Ca1.5GdCe0.5]VIII[ZrFe]VI[Fe x Al3? x ]IVO12

This study was aimed at the synthesis, study of phase relations and characterization of the garnet ([Ca_1.5GdCe_0.5]^VIII[ZrFe]^VI[Fe _x Al_3−x ]^IVO₁₂, x = 0−2) intended as promising matrix for actinides (Pu) immobilization. The optimum temperatures of the fabrication of the garnets ceramics are 1400 °C at x = 2 and 1500 °C at x = 0−1. The garnets lattice parameters and the content of Ce, as an imitator of Pu, increased with the content of iron. It was suggested that the ability of the garnet for incorporation of Pu was closely related to the ionic radii of the elements occupied the four-and six-coordinated sites of the structure.     

Dynamics and chaos control of gyrostat satellite

We consider the chaotic motion of the free gyrostat consisting of a platform with a triaxial inertia ellipsoid and a rotor with a small asymmetry with respect to the axis of rotation. Dimensionless equations of motion of the system with perturbations caused by small asymmetries of the rotor are written in Andoyer-Deprit variables. These perturbations lead to separatrix chaos. For gyrostats with different ratios of moments of inertia heteroclinic and homoclinic trajectories are written in closed-form. These trajectories are used for constructing modified Melnikov function, which is used for determine the control that eliminates separatrix chaos. Melnikov function and phase space trajectory are built to show the effectiveness of the control.     

Controlling the Parameters of a Shock Wave by Means of the Mass and Energy Supply

The process of controlling the parameters of a bow shock created by a body flying at supersonic velocity by supplying mass and thermal energy behind the shock is investigated. The mass and thermal energy were supplied by means of fan air jets flowing out from the body and hydrogen combustion in the neighborhood of the model, respectively. The flow parameters were measured in the neighborhood of the model and recalculated for greater distances. For these control methods some features of the variation of the shock intensity and momentum are presented. A generalization of the effect of the thrust of the nozzles forming the jets and their orientation on the shock wave parameters is obtained. The control methods considered are compared with each other.     

A modular model of the crystal structure of the pyrochlore-murataite polysomatic series

This paper reports on the results of a structural investigation of an important group of synthetic compounds with derivative structures of the mineral murataite, a potential matrix for immobilization of radioactive wastes. A model describing the structure of the entire group of compounds is proposed on the basis of analyzing the results obtained using chemical (electron microprobe) analysis methods, high-resolution transmission electron microscopy (high-resolution electron images and microdiffraction patterns), and X-ray diffractometry of a large array of artificial murataite ceramics. In essence, the proposed structural model is as follows: in the structure, layers of two (pyrochlore and murataite) packing types alternate along the [111] direction of the cubic supercell, so that the resulting structures can undergo substitutional and displacive modulations. Experiments on irradiation of different murataite modifications with heavy ions demonstrate that these modifications have close values of the radiation resistance, which is higher than that of the pyrochlore coexisting with them.     

Thermal Stability of Glass with Simulators of Chloride Highly Radioactive Wastes

Doklady Physics - High temperature behavior of sodium–aluminum fluorophosphate glass—a potential matrix for immobilisation of waste salt electrolyte from pyrochemical reprocessing of...     

Crystalline rocks as a medium for nuclear waste disposal

Crystalline rocks are common for areas of dislocation of radiochemical enterprises in Russia and are the most probable media for construction of underground repositories of irradiated nuclear fuel and high-level radioactive waste. The repositories are supposed to be sited in seismically stable blocks with a low speed of vertical movements, where there is no volcanism and mineral resources. Under these conditions, the only mechanism of biosphere pollution is radionuclide transport by ground waters from the repository to environment. The article considers the isolation properties of crystalline rocks and conditions preventing release of radionuclides from underground repositories.