Satisfactory dense crack—free dispersions of spheroidal UO2 — ThO2 particles in BeO can be produced by "co-sintering", a process in which unsintered particles are hydrostatically pressed in BeO and the dispersion is sintered in one step, the large voids and cracks in dispersions of fully sintered particles in BeO following sintering are related to mismatched sintering shrinkage between the two phases; they are probably indicative of a high interfacial energy between the two phases. Co—sintering has been used for individual fabrication of specimens for irradiation testing, but is not immediately applicable to large scale fabrication of fuel element shapes, Possible modifications of the method are discussed.

Beryllium metal specimens fabricated by various routes were examined after irradiation to fast neutron doses of 5.5 x 1020 to 9 x 1020 nvt at temperatures of 450, 550, and 650ºC. The results were in general agreement with those reported previously for similar material irradiated to lower doses. Density changes of any significance were observed only at 650ºC. Serious loss of high temperature ductility occurred in all materials and was again attributed to helium bubble formation at grain boundaries. Material fabricated by hot pressing and extrusion showed superior properties, both before and after irradiation, to material prepared by loose sintering and extrusion.

A complex of computer programmes called MULGA is described which will produce multigroup cross sections in a format suitable for input into a selection of reactor codes. Always bearing in mind that the spatial variation of flux will frustrate any determination of "exact" cross sections the maximum accuracy has been striven for within the limitations of urgency and feasibility. The programmes; together with an associated microscopic data library tape, and a specialised monitor system, have been coded for an IBM 1620 computer with 4 magnetic tapes. The basic programmes MULGA 1 and MULGA 2 have already been adapted for an ISM 7090 and the whole series will be modified for the new site computer in 1964.

Methods and equipment are described whereby electrical pulses are recorded on magnetic tape in two different ways, using a commercial, single-track type deck, The first method is used to record count rate information regarding regularly or randomly occurring pulses. Random count rates up to approximately 2,000 per second can be directly recorded without serious dead-time loss. By the addition of a simple, high-resolution scale-of-4, the input count rate can be increased to approximately 20,000 per second. By the other method information about relative pulse amplitude as well as count rate is recorded. The usable amplitude analogue output corresponds to an input range of at least 7 to 1, with linearity of approximately 1 1/2 per cent of maximum amplitude. Amplitude resolution of 2 to 3 per cent is obtained over the upper 70 per cent of the range. Transistorized circuitry is described which enables the output pulses of the tape recorder to be analyzed by a Radiation Counter Laboratories Inc. 256 channel scaler-analyzer.

The equation for the H.T.G.C. reactor fuel costs developed previously in AAEC/TM141 has been modified and applied to "heterogenous" fuel systems. Fuel costs are reduced by 20-25 per cent in these systems relative to the "homogeneous" systems; these advantages arise from the longer life which may ben assumed for the unfueled beryllia and cheaper fabrication costs. The effects of reduced beryllia costs on fuel cycle costs are also examined.

Fuel specimens having uranium—thorium beryllides as the fissile bearing phase were irradiated at 400 to 700 ºC to burn—ups between 7 and 11a/0 uranium in a predominantly thermal flux, two specimens of massive (U;Th)Be13 exhibited good dimensional stability and low fission gas release. Dispersion specimens containing 20, 35, and 50v/o (U,Th)Be13 swelled by 3 to 18 per cent, and released up to 33 per cent, of the gaseous fission products. The results indicate that the mixed beryllide is an inherently good fuel material and lead to the conclusion that the poor irradiation stability of hot—pressed specimens may not be typical of (U,Th)Be13— Be dispersions prepared by other techniques.

The numerical solution of the double P/sub 3/ equations in slab geometry, by a forward-elimination back-substitution process, is described and is illustrated by application to a slab self shielding problem and by comparison with the results obtained by analytical solution of the equations.

A method is described for the computation of the energy dependence of the neutron flux and slowing down density in a bare reactor to form the basis of a 7090 Fortran computer program for survey studies of power reactors. Allowance is made for resonance absorption and resonance fission, neutron thermalisation, fast neutron reactions including (n, 2n) and (n, n), and anisotropic elastic scattering.

A method is described whereby the density of a single crystal of beryllium oxide can be measured by suspending it in a dense liquid. The method is being used to measure radiation-induced changes in density and is sensitive to 1 part in 10(5). The absolute accuracy has not been established owing the lack of a suitable standard.

Kalberer and Rutschmann (Helv, Chim, Act, 44 : 1956, 1961) described a method of estimating quantitatively C-14 compounds on a paper carrier, for example chromatograms. The sample is combusted in oxygen, the C14O2 produced being absorbed in ethanolamine solution and counted by liquid scintillation techniques. However, errors occur where there are deviations from their experimental conditions, such as in counting equipment or weight combusted, owing to differing concentrations of dissolved oxygen in counting solutions. Those errors can be eliminated by scrubbing the ethanolamine absorption solutions with nitrogen before they are mixed with the liquid scintillant. Furthermore, by this additional step, the range of weights combusted can be extended form 130 - 200 mg to 0-200 mg.

Order-of-magnitude estimates of the fast neutron elastic scattering rate have been obtained to supplement metallurgical studies of the fast neutron damage in some small beryllium oxide-based dispersed fuel specimens. The elastic scattering rate for neutrons with energies above 0.1 MeV is shown to be of the the order of 30 per cent of the fission neutron release rate in the specimens, owing to significant fast neutron leakage. The ratio of the Be (n,2n) reaction rate to the fission neutron release rate in the specimens is of the order of only 6 per cent of its value for an infinite medium of beryllium oxide.

Modifications to the A.A.E.C.'s Siemens Diffractometer are described which enable precision lattice parameter determinations on single crystals. Analysis of the errors and consideration of results suggest that accuracies of about 1--2 parts in 10/sup 5/ are obtained on small beryllium oxide crystals. Details of alignment and measurement procedure are included.

The results of unclassified experiments on the irradiation behaviour of BeO fueled with UO2 and (U,Th)O2 are summarized and discussed. The overall picture is still somewhat confused owing to the different experimental conditions used by different workers. A serious deficiency in most of the work is the failure to quote the energies of the irradiation neutrons and it is not clear whether the observed changes are due to fission fragment or fast neutron bombardment. The irradiation behaviour, in general, appears to be good up to fission doses of at least 5 x 10(20) fissions cm-3 of dispersion.

A summary of the available literature on the development of the various processes for the separation of uranium and thorium from aqueous nitrate solutions is presented. Flowsheets are given corresponding to the various stages in the development of the Thorex processes.

This manual gives a description, operating instructions, circuit diagram and parts list of Transistorised Temperature Controller type 30 designed in the laboratories of the Australian Atomic Energy Commission.

This manual is intended to give operating and maintenance information for the range of counting equipment in use by the A.A.E.C. at Lucas Heights, designation of Scaler Type 2A. This equipment has been designed in the General Physics Section of the A.A.E.C. General Nucleonics Division. The equipment was built by an Australian manufacturer (Siemens Nucleonics).

Samples of vermiculite from Young River, W.A., and Kingaroy, Qld., have tested for cation exchange capacity using batch and column experiments. The better material, Young River vermiculite, was given more exhaustive column tests to determine the optimum particle size and to investigate its selectivity for caesium ions in the presence of higher concentrations of competing ions. At the optimum particle size of (-30+60) B.S.S. the cation exchange capacity of Young River vermiculite was approximately 70 meq/100g. With competing cations in solution caesium breakthrough occurs after a very small volume of influent has passed through the bed. It was concluded that neither of these vermiculite minerals would be suitable of medium level radioactive waste treatment.

Samples from possible zoolite bearing deposits have been tested for cation exchange capacity using batch and column experiments. The best material, Eagleton Quarry pink shale, was given more exhaustive column tests to determine the effect of mineral particle size, influent flowrate, and the presence of competing cations on caseium breakthrough. Diffusion of caesium ions through the mineral particle controls the ion exchange process. At the optimum size of (-30+36) B.S.S. the cation exchange capacity of Eagleton Quarry pink shale is approximately 60 meq/100g. With competing cations in solution the caesium breakthrough occurs after very small influent volumes have passed through the mineral bed and it was concluded that non of the minerals tested would be suitable for medium level radioactive waste treatment. A sample of clinoptilolite from Hector, California was also test for caesium selectivity.

Data relating to the binary and ternary systems involving beryllium oxide are presented . The survey deals with all available literature up to December 1962.

This report summarises all the results obtained to date from a programme on the effects of neutron irradiation on the properties of beryllium metal. Results are presented on changes in density and mechanical properties in material fabricated by various routes and irradiated to fast neutron doses from 1019 nvt to 6 x 1023 nvt and at temperatures in the range 75ºC — 700ºC, Summaries of electron microscopy observations and electrical resistivity measurements, which are reported in more detail elsewhere., are also given, It is concluded that all the observed property changes can be interpreted in terms of the distribution of helium which is produced by fast neutron transmutation reactions in beryllium and that damage due to defect production is negligible for irradiation temperatures of 75ºC and above. Density changes duetoheiium bubble formation are shown to be very small but serious deterioration of mechanical properties can occur. The mechanical property changes and the distribution of helium are shown to be very dependent on material history and on the irradiation temperature. The standard Lucas Heights hot extruded material is shown to retain good mechanical properties for irradiation temperatures above 550ºC but serious loss of low temperature ductility is found to occur for …

The diffusion length of thermal neutrons in beryllium oxide of effective density 2.86 g cm-3 has been measured as 29.9 +- 0.8 cm. Using published experimental values for the diffusion constant of beryllium oxide, a value of [sigma] a = 9.0 +- 0.5 mb is deduced for the effective 2200m/s microscopic absorption cross-section.

The design of prestressed concrete pressure vessels is discussed and some approximate design formulae are developed. The design and performance of vessels reported in the literature are reviewed and an approximate comparison is made of steel and concrete pressure vessels for a particular case. Concrete vessels are attractive for moderate temperatures and pressures because of the large size of vessel which can be built and the non-explosive mode of failure. However it is unlikely that large cost savings will be made by using prestressed concrete instead of steel for the pressure vessels.

When beryllium is irradiated by fast neutrons, helium is produced by the (n,2n) and (n,α) transmutation reactions. Electron microscopy techniques have been used to study the nucleation and distribution of helium bubbles in several different grades of beryllium, after irradiation at temperatures in the range 75 — 700ºC. The effect of post-irradiation annealing is also reported. It is shown that for similar neutron doses and irradiation temperatures, there were wide variations in helium bubble size and distribution in specimens of beryllium fabricated by different methods. The most satisfactory material was that fabricated from Pechiney powder by direct hot extrusion followed by annealing for one hour at 800ºC and air cooling, it is suggested that the helium bubbles nucleate on second phase precipitates and that the distribution of this phase is strongly affected by fabrication and heat treatment.

An IBM 1620 program is described that calculates the Bragg angles for cubic, hexagonal, and tetragonal crystal systems for use with powder x-ray diffraction techniques. Allowance is made for absent reflections in the case of face- and body-centered cubic and close-packed hexagonal materials.