Structure of heterosystems formed by a SnO<Subscript>2</Subscript> film and island metal (Ag,Au, or Pd) condensate

We have studied the phase composition and microstructure of thin tin(IV) oxide films surfacemodified with silver, gold, and palladium nanoislands. Using high-energy electron diffraction, we have shown for the first time that the thermal oxidation of the Sn films leads to the formation of nanocrystalline multiphase SnO₂ films in which the major phase is orthorhombic. Also present are (in order of decreasing content) tetragonal and cubic phases. Blocks of SnO₂(O) subgrains with 〈101〉 texture contain dislocations and stacking faults, which are interpreted as layers of the tetragonal phase. It has been shown that vacuum condensation makes it possible to modify the surface of SnO₂ films with noble metals and obtain homogeneous nanoisland coatings characterized by a unimodal, uniform island size distribution.     

Electrical Conductivity of a Carbon Reinforced Alumina Resistive Composite Material Based on Synthetic Graphite and Graphene

We have prepared samples of carbon reinforced alumina ceramics with different volume fractions of synthetic graphite (0–20%) and graphene (0–4%) and measured their electrical conductivity. It has been shown that increasing the volume percent of the conductive component increases the electrical conductivity of the samples from 10^–8 to 2 × 10^–3 S/cm. The results have been analyzed in terms of percolation theory and tunneling conduction theory. The synthetic graphite-based samples show linear current–voltage behavior and their electrical conductivity increases by a factor of 1.4 to 2.8 in the temperature range 300–550 K, with a sharp rise above 550 K. The temperature dependences of their electrical conductivity are analyzed in terms of hopping transport and thermally induced tunneling conduction mechanisms. The conclusion is made that the conduction mechanism in the corundum–carbon ceramics differs significantly from that in polymer composite materials.     

Use of safety valves in the first loop of a nuclear power plant with a water-moderated-water-cooled power reactor

Conclusions It is not useful to transfer the requirements of the supervising committees on the safety of the usual vessels and high-pressure systems against their exceeding the allowable value of the pressure in nuclear installations with the conditions of radioactivity in the first loop of nuclear power plants, especially those onboard a vessel, with such a system as the active zone, which does not permit exposure and prolonged liberation of heat. Protection against an increase in pressure can be more effectively provided by reliable systems for shutting down the reactor, removing heat, and others, which is indicated by the comparative experience in using nuclear-powered icebreakers and some nuclear power plants abroad.Translated from Atomnaya Énergiya, Vol 50, No. 5, pp. 308–310, May, 1981.     

Fuel elements of nuclear reactors

On the basis of foreign reports presented at the Second International Conference on the Peaceful Uses of Atomic Energy, Geneva, 1958, the characteristics of construction of fuel elements (FE) and basic data relating to them for a series of reactors are given. Problems on the selection of fuel and construction materials as well as the technology of preparing FE for various types of nuclear reactor are examined.