Pechiney and Brush UOX BeO differ markedly in fabrication behaviour, only Brush UOX being readily sinterable. A comparative study of the two powders has shown few outstanding differences in powder properties. Both are of high purity but contain free and combined moisture to the extent of about 1.5 per cent. Pechiney BeO has a larger mean crystallite size (0.2 — 0.3μ) than Brush UOX (0.1 — 0.15μ) and a larger range of crystallite size, and both contain a small proportion of crystallites of size 1μ. and larger. The tap density of UOX is much lower than that of Pechiney, and its surface area is higher by a factor of two, UOX BeO can be hot—pressed or cold—pressed and sintered to high densities at temperatures of 1400º and 1500ºC respectively, which are approximately 300ºC lower than those required for Pechiney. Grain size of fabricated material increases with fabrication temperature in both grades, and at the same temperatures is larger for UOX than Pechiney. However, at comparable densities grain sizes are also comparable for the two materials, The bend strength at room temperature of hot—pressed Pechiney BeO reaches a maximum of approximately 30,000 p.s.i. when pressed at 1750ºC. Above this temperature the …

Beryllium is a favoured canning and/or moderating material in the proposed Australian High Temperature Gas Cooled Reactor. With carbon dioxide as the most likely coolant a detailed knowledge of the corrosion of beryllium in this gas is required. Two separate investigations have proceeded simultaneously. First the effect of the following variables was studied; surface preparation of the specimen, temperature (100—725ºC), pressure (0—280 p.s.i.g.), velocity, and impurity content of the gas. The influence of irradiation has not yet been studied. Autoclaves, thermobalances, and dynamic loops were used. The results were statistically analysed and kinetic data obtained. In all cases specimens with etched surfaces yielded approximately 25 — 30 per cent, greater weight gains than specimens with ground or polished surfaces. On extruded material no "breakaway" oxidation was encountered below 650ºC in commercially dry gas (< 20 p.p.m. moisture). The rate of attack was to some extent affected by the pressure of the gas. Breakaway was only observed in one series of specimens at 650ºC. In this particular case the gas pressure was 280 p.s.i.g. However, it seems that surface temperatures of beryllium cans made from extruded material should be maintained below 650ºC in a reactor system using the commercially pure carbon …

An investigation of the solvent extraction behavior of salicylato- beryllium complexes is reported. A simplified method for calculating the stability constants has been developed. The values obtained are beta /sub 1/ = 4.0 x 10/sup 12/ and beta /sub 2/ = 4 3 x 10/sup 22/ in 0.15 M sodium perchlorate. (auth)

The high flux research reactor HIFAR contains ten tons of heavy water which acts as moderator and primary coolant. Over an eighteen months period regular microbiological examinations have been carried out on samples of heavy water taken from various parts of the circuit. The heavy water circuit provides an interesting opportunity for the study of microorganisms because of the high isotopic purity (greater than 99.6 per cent.), and the high chemical purity of the heavy water in the reactor. Furthermore, during its passage through the reactor core the water and suspended bacteria are subjected to intense irradiation, the neutron flux being approximately 10 14 neutrons cm-2 sec-1. The presence of bacteria in the heavy water circuit has been demonstrated and experimental results and methods used are discussed. Some evidence is presented to show that the ion—exchange resin bed contributes nutrients to support bacterial growth.

The extraction of beryllium by triisooctylamine is measured over the pH range from 1 to 10, in the presence of malonic, maleic, succinic, phthalic, and salicylic acids. Values are obtained for the stability constants of the various metal-acid complexes by potentiometric titration. The degree of extraction is dependent on the abundance of the anionic complex present in the aqueous phase and this is in turn dependent on the strength of the corresponding acid and the stability of the complex. (auth).

The slowing down spectra of neutrons were obtained for heavy water, light water, and mixtures of heavy water and light water. It was assumed that fission neutrons are produced uniformly throughout an infinite moderator and the only process considered was elastic scattering, spherically symmetric in the center-of-mass system. The (n,2n) reaction with the deuterium nucleus and absorption were assumed negligible. The average transfer cross section, fast diffusion coefficient, the slowing down area, and average velocity ratio were obtained for two-group calculations using the epithermal spectra. (auth).

A description is given of a method suitable for the automatic solution of certain optimum design problems on a digital computer for cases where the number of constraints imposed on the design is not greater than the number of design variables. The problem is transformed to one requiring the minimization or maximization of an unconstrained function, for which a gradient method is used.

Breakaway corrosion of Be in moist CO2 can be avoided if the Be is fabricated using preoxidized powder. The powder is preoxidized by heating in dry O/sub 2/. Preoxidation of Be powder was measured as a function of temperature and time of heating in O/sub 2/. The subsequent reactions of the preoxidized powder in moist CO/sub 2/ at 700 deg C were studied and the effect of increasing amounts of added oxide was measured. A model is proposed to explain the inhibition of corrosion by added oxide. (auth)

A method is presented for the analysis of transient temperatures in a homogeneous circular cylindrical fuel element in a coolant channel with no axial conduction and no heat loss to the channel wall. In addition, some results were obtained for mean fuel element temperatures in power transients for a simpler model, but accounting for details of the axial coolant temperature distribution in the unsteady state. (auth).

Comparison of the adsorption characteristics of the desiccants silica gel, alumina, and molecular sieves has shown that molecular sieves have by far the greatest capacity of the desiccants at the low partial pressures considered. Equilibrium data in the form of isotherms were established over the range of variables expected in the coolant circuit of a proposed Australian H.T.G.C. reactor. The mass transfer from the gas phase to molecular sieves is such that no correlation could be attempted for the adsorption zone height; the height proved to be too small.

Concentric tubular reactor fuel element geometries to give equal coolant outlet temperatures are presented. Oscillations from tube to tube in thickness and temperatures generally occur but it is possible to eliminate them by choice of the centre element. This may be a fuel rod or a non-heat—producing rod with or without a surrounding annulus of fuel. The geometries and temperatures are dependent on the voidage and on a non-dimensional parameter equivalent to a Biot number based on the channel equivalent diameter.

A programme is described for determining the neutron enhancement due to the (n,2n) reaction in a reactor moderated by beryllium. For moderation by pure beryllium the enhancement has been found to be 9.7 per cent.