[en] A methane pellet moderator assembly consisting of a pelletizer, a helium cooled sub-cooling tunnel, a liquid helium cooled cryogenic pellet storage hopper and a 1.5L moderator cell has been constructed for the purpose demonstrating a system for use in high-power spallation sources. (orig.)

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[en] In order to select the most suitable mixtures for cooling the Reactor DON, in project, within the group of polyphenyl compounds, which at present time prevails in organic nuclear power reactor philosophy, the following subjects are going to be studied: 1. Static and dynamic experiences of thermal and radiolytic stability of commercial polyphenyl mixtures. 2. Studies on purification of the damaged coolant and search for possible applications of the residual polymers. 3. Analytical control and measurement of the physical constants of the polyphenyl mixtures. (Author)

[en] A neutronic reactor is described comprising a moderator including horizontal layers formed of horizontal rows of graphite blocks, alternate layers of blocks having the rows extending in one direction, the remaining alternate layers having the rows extending transversely to the said one direction, alternate rows of blocks in one set of alternate layers having longitudinal ducts, the moderator further including slotted graphite tubes positioned in the ducts, the reactor further comprising an aluminum coolant tube positioned within the slotted tube in spaced relation thereto, bodies of thermal-neutron-fissionable material, and jackets enclosing the bodies and being formed of a corrosion-resistant material having a low neutron-capture cross section, the bodies and jackets being positioned within the coolant tube so that the jackets are spaced from the coolant tube. 2 claims, 9 figures

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[en] The object of this study was to investigate the effect of different doses of gamma radiation on some specific groups of soil bacteria, namely Azotobacter and Clostridium. The reproliferation of these two groups following the exposure to gamma radiation was also investigated. Two soil samples were used in this study, the first was calcareous from the northern coast of Egypt and the second was alluvium from Bahtim. The investigated doses of gamma radiation were 0,100, 250 and 1000 Krad. The study revealed that both Azotobacter and Clostridium were affected with different magnitude by the gamma irradiation treatments. However, the survivity of Clostridium to gamma irradiation was greater than Azotobacter. The survivity of Azotobacter and Clostridium was more pronounced in the alluvial than in the calcareous soil sample. It was shown that increasing time of incubation after exposure to gamma radiation generally increased reproliferation of Azotobacter and Clostridium; being more marked with Clostridium than Azotobacter. (author)

[en] In the present report an expression is deduced for the spectral distribution of flux of over a few hundred electron volts; it is valid for most cases of thermal neutron reactors. This expression is: Ψ(E) = K [Ψ_o(E) + h ψ_e(E)] Ψ_o(E) is the so-called 'homogeneous' constituent of the flux; it corresponds approximately to the case of an infinite homogeneous medium; it is of the type: Y(V - E) e^(b√E)/E + Y(E-V) F E^υ e^-βE The parameters V and F are such that Ψ_o(E) and its derivative are continuous at the junction energy V. Ψ_e(E) is the 'heterogeneous' constituent of the flux; it is of the type: E^υ e^-βE. The various parameters of Ψ(E) are on the one hand characteristic of the nature of the reactor moderator, and on the other hand determined by a resonant flux measurement and one, or possibly two, measurements using a fast neutron threshold detector. We have been led furthermore to define an expression for the threshold reaction section which is more exact than the conventional transition function. (author)

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