Interrelation between the grain orientation and the radiation growth of uranium rods

The results obtained in radiation tests of -heat-treated uranium rods at temperatures of 200–300; 450–470; 480 C are given. Dependences of the radiation-growth coefficients G_i on the growth index GI characterizing the grain orientation of the tested specimens were plotted. The elongation component resulting from the radiation growth due to grain orientation was determined. The dependence of the radiation-growth coefficient on the test temperature for weakly-pronounced grain orientations is given. It is shown that the mean values of the linear thermabexpansion coefficient measured in one direction only, do not provide information on the character and degree of the grain orientation if the latter is not uniaxial.Translated from Atomnaya Énergiya, Vol. 18, No. 4, pp. 357–361, April, 1965     

New model of equiaxial growth of uranium dioxide grains under irradiation conditions

Conclusions The experimental data give evidence of a retardation in the growth of equiaxial grains when oxide fuel is irradiated. This retardation in grain growth can be explained as being due to the formation of short-lived defect structures on the grain boundaries under the action of irradiation. An analysis of a broad spectrum of experimental data indicates that a model based on this hypothesis correctly predicts the growth of equiaxial grains in a wide range of temperatures, irradiation intensities, and fuel depletions. The work was carried out with the partial support of the Russia Fund for Fundamental Research under grant number 96-02-18686. State Scientific Center of the Russian Federation, Institute of Innovative and Thermonuclear Research, Troitsk. Translated from Atomnaya énergiya, Vol. 84, No. 4, pp. 329–334, April, 1998.     

The irradiation test of inert-matrix fuel in comparison to uranium plutonium mixed oxide fuel at the halden reactor

Conservative modelling for pin layout shows that the relatively low thermal conductivity of Inert-Matrix Fuel (IMF) causes higher temperatures and therefore higher fission gas release than in uranium plutonium mixed oxide (MOX). According to neutronic calculations, performance differences will also arise from different evolutions of the respective radial power and burnup distributions. Modelling of these effects as well as a 10% greater production of Xe in the thermal spectrum of the Halden reactor is well within the capabilities of appropriate codes. Some of the data and models used for the pre-calculations are preliminary and will be revised after the first experimental data have become available.     

Thyroid gland irradiation doses for moscow inhabitants following the reactor accident at Chernobyl

Conclusions As a result of the Chernobyl nuclear power plant accident, there was a significant increase in the contamination level of the environment by a series of radionuclides, and specifically iodine isotopes. The iodine isotope content of the atmosphere was lower than the permissible level, and quickly diminished with time.The thyroid gland irradiation doses of the population accumulated, for the most part, as a result of the entry of¹³¹I into the milk supply.The entry of¹³¹I into the population continued only for a short period of time, and the total thyroid gland irradiation dose was lower than permissible levels.Translated from Atomnaya Énergiya, Vol. 68, No. 1, pp. 49–51, January, 1990.     

The release of radioactive gases from uranium dioxide during irradiation

The steady-state release of radioactive rare gases has been measured during the isothermal irradiation of small-grained, largegrained and single-crystal UO₂. The experiment showed that (a) gases with half-lives less than five days exhibit no indication of enhanced grain-boundary diffusion; (b) the rate of release is a complex function of rating, but within the range of the experiment, the release rate was independent of rating; (c) the release kinetics for each gas are unique with no common relationship between fractional release and the gas decay constant; (d) the results show that the diffusion coefficient of xenon is ten times that for krypton at a temperature of 1450°C.     

The effect of neutron irradiation on the precipitate distribution in adjusted uranium

Precipitates in α-uranium are thought to be very important in controlling the swelling that occurs in the reactor. Cross sections from the 30 mm diameter adjusted uranium fuel bars were cut and heat-treated to give a UAl₂ precipitate distribution peaking at about 30 nm diameter. Alternate sections were irradiated to 500 MWd/te at 673 K. Comparisons before and after irradiation show that a new precipitate population is formed during irradiation. Since new precipitates can form, mechanisms of swelling resistance based on the effects of aluminium in solution are no longer tenable.     

The provision of radiation safety of personnel in the extraction of uranium ores

The radiation hazard to the respiratory organs of miners in uranium mines is assessed and a set of measures is worked out for ensuring radiation safety in the prospecting and extraction of uranium ores. Measures are described and justified which, as a result of achieving them, enable a standard to be set for a mining atmosphere and also to prevent external radiation overexposure and radioactive contamination of the integumenta of people working in the uranium mines.Translated from Atomnaya Énergiya, Vol. 19, No. 2, pp. 161–168, August, 1965     

The characteristics of fission gas release from monocrystalline uranium dioxide during irradiation

Release rates for ^85mKr, ⁸⁷Kr, ⁸⁸Kr, ¹³³Xe, ¹³⁵xe and ¹³⁸Xe were measured in the temperature range 700–1550°C. The data were analysed in terms of diffusion of the rare gases and their halogen precursors. The diffusion coefficients for xenon and iodine were found to be similar whilst krypton also had a similar mobility at ~1200°C but otherwise diffused more slowly. Bromine had a high mobility compared with the rare gases (X 200).     

The effects of intergranular constraints on irradiation growth of Zircaloy-2 at 320 K

Dimensional changes during neutron irradiation of crystallographically textured Zircaloy-2 has been found to be a complex function of its thermal and mechanical treatments. A model is presented here to investigate the influence of intergranular constraints on the irradiation-induced growth. Good qualitative agreement has been obtained with experimental data for dimensional changes observed in unstressed material, in that, (a) the normal anisotropy of growth, resulting from expansion along a axes and contraction along c axes can be reversed by prestrain, (b) annealing can introduce intergranular stresses due to the anisotropic thermal expansion, which result in a wider variety of dimensional behaviours than expected from crystallographic texture only, and (c) the intergranular stresses from prestrain are gradually relaxed during irradiation and normal anisotropy eventually returns.