Journal of Nuclear Energy. Part B. Reactor Technology最新文献

The development of new methods for measuring ionizing radiation is a current problem. The use of crystals as detectors seems particularly promising and the present paper is devoted to the question of using as detectors in dosimetry cadmium sulphide photo-conductors, which possess considerably greater sensitivity to various forms of radiation than air ionization chambers. The high sensitivity of small CdS crystals allows them to be used for solving several problems of dosimetry. A review of Soviet and foreign papers on this topic is given. Methods of obtaining polycrystalline and single-crystal photo-conductors based on CdS are briefly considered, together with their dosimetric, time and temperature characteristics. Some shortcomings of CdS detectors and possible ways of overcoming them are indicated. Circuits of actual CdS dosimeters are given.

An empirical approach is proposed to the determination of a constant (B_o²) of the materials of the critical assembly which corresponds to the material buckling.

By using two empirical equations and the one-group geometrical buckling relations any change of geometry, reflected by hydrogenous materials or unreflected, may be accomplished for simple shapes.

Using uranium containing 0·1 per cent cerium as a simple model of irradiated fuel, the degree of ‘poison’ removal by selfslagging methods has been found to be comparable with that achieved at very low alloying concentrations. By filtration through oxide beds, removals of 95 per cent Ce have been obtained, the speed of processing being limited only by the time required to reach operating temperature.

Some information is presented on the behaviour of inclusions and the mechanism of cerium removal from the alloys.

Experimental data on heat transfer to liquid metals are often conflicting and do not accord with theoretical results. The reasons for these discrepancies have not been clear. The present work shows that the main reason for the disagreement is the thermal resistance between the heated surface and the liquid metal. This conclusion is reached from calculations of the heat transfer coefficient by two methods: from measurements of the temperature distribution in the moving liquid and from measurements of the wall temperature. The former agrees with the distribution calculated from Lyon's equation. It has been found that the presence of oxygen in a sodium-potassium alloy reduces the heat transfer coefficient. The results of experiments with no contact thermal resistance agree with those of Isakoff and Drew and of Brownet al.

A description is also given of the experimental apparatus, the test section, and a thermocouple whereby the temperature distribution in a stream of liquid metal can be measured.

An equation in dimensionless groups has been proposed by the author on the basis of experimental data on critical heat fluxes in forced convection of sub-cooled water at pressures between 100 and 210 atm. A simplification of this equation at low pressures is predicted from theory.

It is shown that the dimensionless equation previously given is valid over a wider range of pressures, namely from 35 to 210 atm.

The reduction of published experimental data concerning qcr at low pressures confirms the theoretical conclusion that the functional relations between one group to be determined and two determining groups become degenerate at water pressures near atmospheric and therefore that the dimensionless equation simplifies in this case. From this equation a formula is derived which can be used for calculations at pressures between 1 and 15 atm.