[en] During a postulated severe incident with core rupture at a sodium cooled fast reactor major quantities of fuel particles may be suspended in the liquid sodium contained in the core catcher. The release of fuel and sodium from a contaminated pool at 500 and 900⁰C was investigated by laboratory and technical experiments. Sodium vapor was released from a boiling sodium pool into nitrogen atmosphere with a rate of 85 kg Na/m².h. Decontamination factors for uranium release from sodium pools were measured between 10³ and 10⁴ for sodium containing 1 weight percent UO₂ powder. The effect was found to be not strong dependent on temperature between 500 and 900⁰C

[en] The optimum conditions for MHD power generation with only Joulean dissipation were derived from the thermodynamic First and Second Laws. The condition from the First Law was obtained by determining the optimum functional form of polytropic exponents against the load factor for a given interaction parameter. The other conditions from the Second Law were the spatial constancy of the ratio of magnetic body force to the static pressure for a compressible plasma and the spatial constancy of σu²B²/ρT for an incompressible plasma. The proposed optimum generator for a compressible plasma exhibited approximately 25% higher efficiency than that of the conventional constant velocity and constant magnetic field type generator for the moderate values of interaction parameters. Both the Faraday- and Hall-type generators exhibited the same load characteristics when the condition of minimum entropy increase was introduced. Thus optimal load factor giving the maximum thermal efficiency for the proposed optimum generator was V = 0.5. The introduction of non-adiabatic losses produced a slight shift of the optimal values of the load factor and hence reduced the efficiency. However, the efficiency was extensively recovered when the spatial constancy of σuB²/p was extended for the non-adiabatic case and exhibited the maximum at V = 0.5. (author)

[en] Simplified formulae were derived for the approximate evaluation of electrical performances of an MHD generator with nonuniform equilibrium plasma. In order to clarify the effectiveness of the properly shaped nonuniform magnetic induction of the type B varies as nsub(e), the transverse component Bsub(y) was included in the formulation of the theory. It was shown that the terminal characteristics of the generator, such as the internal resistance, the motional emf, the current and the output power could be improved significantly under the shaped Bsub(z) varies as nsub(e) type of applied magnetic induction for wide ranges of electrode- and insulator wall temperatures, channel sizes and averaged intensities of the magnetic induction. (author)

[en] To develop a convenient and sensitive surface contamination monitoring system, the feasibilities of an electret dosimeter using a thin polymer electret and piezoelectret sensor have been examined. To reduce the amounts of radioactive wastes, major interest has recently turned to the low-level radioactive wastes for which the contamination level is less than the de minimis level, which allows treatment as reusable waste. While official de minimis levels have not been set, average levels are presumed to be 10^-6 and 10^-4 μCi/g for alpha and gamma contamination, respectively. The regulatory unit is the weight of radioactivity, but alpha contamination cannot be measured without a surface value. So the authors examined a surface contamination monitor, which was particularly suited to alpha measurements. Although electret dosimeters have been developed of the ion chamber type, the electret dosimeter using only a polymer foil was investigated

No abstract available

[en] The most serious impact of animal disease on livestock productivity in developing countries derives from its effect on overall livestock production and trade development rather than from the direct losses it causes. The global importance of major infectious diseases such as foot and mouth disease, rinderpest and African swine fever is reviewed. The impact of major livestock diseases in tropical Africa on livestock productivity and economic losses is analysed, and the importance of in-depth analysis of the disease impact on livestock and rural development is stressed. Lack of diagnosis facilities that are needed to acquire reliable information on the distribution of disease is often a major constraint to cost-benefit analysis of control options. However, enough evidence exists to substantiate the fact that improved disease control is a prerequisite for progress towards increased productivity based on the adoption of more intensive production systems and use of animals of improved genotype. Veterinary services in developing countries are at various stages of development, and the priority order of infra-structure, manpower and technological development for disease control programmes should be carefully planned and be based on socio-economic, cost-benefit and feasibility studies. (author)

[en] In this paper, we review the detailed study of epitaxial growth of β-FeSi₂ films by reactive deposition epitaxy (RDE), multilayer technique and molecular beam epitaxy (MBE). The p- and n-type β-FeSi₂ was formed when it was grown under an Fe-rich and an Si-rich condition, respectively. The maximum electron and hole mobilities of the β-FeSi₂ epitaxial films reached 6900 and 13000 cm²/V·s for the n- and p-type β-FeSi₂, respectively, at around 50 K. Room temperature (RT) 1.6 μm electroluminescence (EL) was realized by optimizing the growth conditions for p-Si/β-FeSi₂ particles/n-Si structures prepared by RDE for β-FeSi₂ and by MBE for Si

[en] Electrical characteristics of a Faraday-type MHD generator with a transversally shaped field configuration (SFC) of magnetic induction were investigated experimentally by using shock heated plasma. The magnetic induction was sharply reduced near electrodes in order to minimize the electrical losses caused by the Hall effect and the conductivity nonuniformity in the boundary layer. The performance of the proposed generator was experimentally compared with that of the conventional type with a uniform field configuration. It was shown that the apparent conductivity, the output power, and the internal resistance were markedly improved in the SFC design, namely, by a factor of from about 1.5 to 2.0. The experimental characteristics agreed qualitatively with results of three-dimensional computer simulations. A possible arrangement of the superconducting coil for the generation of the SFC for a full-scale MHD generator channel was also proposed

[en] To evaluate the release source of cobalt from heater tubes of the feed water line, release rate measurements were carried out by detecting ⁶⁰Co released from irradiated stainless steel in contact with neutral water at an oxygen concentration of 20 ppb. The dependences of cobalt release rate on temperature, flow velocity and exposure time were studied after 670 hours of release experiments, and an empirical equation (which is presented) was obtained in the temperature range from 150 to 240 deg C. A decrease in the cobalt release rate above 250 deg C was considered due to the formation of a protective oxide layer. From these data, the amount of cobalt released from individual feed water heaters was evaluated. It was demonstrated that low cobalt containing stainless steel was economically applied only in the higher temperature region of the heater (20% of the total surface) to reduce cobalt feed rate into the reactor (to approx. 1/2). (author)

[en] A fixed-point radiation monitoring system based on the gated counting method, which was previously reported by us, was constructed for a 45-MeV electron LINAC facility. It was tested under different beam intensities of the accelerator both at the current and repetition rates. It showed excellent dynamic response (from 2.5 X 10(-11) to 1.0 X 10(-8) Sv h-1) to the intensity variation of the radiation source. It was demonstrated that the system was very useful in monitoring an extremely low-level radiation from a pulsed source