Search

A mathematical model of the crystallization of uranium in a continuous linear crystallizer, designed for the crystallization separation of desired products in the processing of an irradiated nuclear fuel, is proposed. This model defines the dynamics of growth/dissolution of uranyl nitrate hexahydrate crystals in a nitric acid solution of uranyl nitrate. Results of a numerical simulation of the indicated process, pointing to the existence of stationary conditions in the working space of the crystallizer, are presented. On the basis of these results, the characteristic time of establishment of the stationary regime at different parameters of the process was estimated. The mathematical model proposed was validated on the basis of a comparison of the results of calculations carried out within its framework with experimental data.

The problem of inelastic scattering of Mossbauer radiation on the order-parameter fluctuations near phase transitions is considered by means of restricted scaling. Expressions for the scattering intensities that are valid for a wide class of objects with gapless dispersion of the fluctuation spectrum are obtained. In extreme cases (i.e. hydrodynamic and critical ones) the line shape of the resonance nuclear absorption is analysed depending on the temperature and the collimations of radiation beams.

There is particular importance in the storage of high-level wastes (for example, vitrified ones) in the stability of the solid matrix (glass) containing radionuclides. This paper examines the most rapid process in glass component redistribution near inhomogeneities (inclusions, pores, cracks, etc.), as these inevitably arise during vitrification. The authors consider two model problems, whose solutions enable one to estimate the changes in component concentrations near inhomogeneities.

The authors construct a geochemical and hydrological flow model for a salt deposit destined as a disposal site for radioactive wastes which depicts the temperature-dependent dissolution, diffusion, and migration of brines and salt mineral inclusions which have come into thermal or direct contact with the waste material. The model also incorporates the effect of insoluble admixtures to the wastes on the inhibition of radionuclide migration throughout the deposit.