The effects of fission fragment damage on vacuum hot pressed fuel specimens of (UTh)Be(12) dispersed in a beryllium matrix were examined by irradiation in a predominantly thermal neutron flux. Damage equivalent to that caused by a 4 x 10(19) to 11 x 10(19) fissions per cm3 (depending on specimen compositions) was achieved at temperatures between 435 degrees and 530 degrees C. All specimens increased in volume on irradiation. The increases ranged from 0.1 per cent to 5 per cent, depending on the volume fraction of fuel phase and the number of fissions per cm3. Some of the volume change -- possibly up to 0.7 percent -- was due to thermal effects alone. Release of fission gases was as high as 2 percent, in some cases and was generally higher than would be expected from recoil in specimens having an open porosity. The fractional release was greater in specimens which experienced a high volume increase. Microstructures showed no significant change on irradiation. All specimens were slightly porous before before irradiation and it is considered that the swelling of specimens was due to the growth of existing pores and that the release of fission gases was facilitated by an increase in open …

Alloy steels were studied to find types suitable for nuclear use in carbon dioxide-cooled reactors at temperatures in the range 400 - 600 degrees C. The corrosion of 2 1/4% Cr, 1% Mo steel in carbon dioxide was measured in the temperature range 460 degrees to 525 degrees C and the gas pressure range 0 to 225 p.s.i.g. The effect of gas velocity, specimen surface treatment, and water content of the gas were also determined. Adherent oxide scales of the Fe3O4 - Fe2O3 type were formed under semi-static conditions together with an unidentified spinel. A Cr2O3 film was never formed under any conditions. Weight gain depended mainly on temperature and varied little with gas pressure, surface treatment, or water content of the gas. The relationship between weight gain and time varied between parabolic and cubic with weight gains ranging from 1.7 ms/cm2 to 5.7 mg/cm2 after 1000 house exposure within the temperature range investigated. Estimated penetration depths after 10,000 hours ranged from 6.8 x 10(-4) to 18.5 x 10(-4) inches. In high velocity gas, that is, at 150 ft/sec, weight gains varied from 0.7 mg/cm2 at 460 degrees C to 2.0 mg/cm2 at 525 degrees C after 100 hours. No …

Specimens of beryllium oxide based dispersion fuels containing between three and twenty-six volume per cent, of U02— Th02 solid solution were irradiated to fission densities of 2 to 14 x 1019 fissions/cm3 of total specimen (equivalent burn—ups of 80 to 230 per cent.) at temperatures of 600 - 850ºC. The experiment was primarily designed to investigate fission product damage although some fast neutron damage did occur in the matrix, the specimens showed excellent resistance to fission product damage; dimensional changes were small, fission product escape was generally only that expected by recoil and there was no sign of cracking due to thermal stresses although these reached estimated values of about 30,000 p.s.i. in some specimens, Metallographic examination showed that some weakening of the matrix grain boundaries had occurred and some preliminary x-ray results suggested that the matrix was in a state of strain. It is suggested that these effects could be due either to fast neutron damage in the matrix or swelling of the fuel particles. The experiment did not provide any conclusive evidence for the superiority of coarse fuel particles (100 - 180μ.) over fine fuel particles (< 10μ) although the dimensional changes and the degree of matrix strain …

A simple matrix formalism is developed to facilitate the application of the double PN method of spherical harmonics to multiple slab configurations, representative of some of the basic neutron transport problems in the theory of nuclear reactors. Special attention is given to the double P2 and P3 approximations, and the results of numerical computations are compared with known accurate results.

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.

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 …

This program was prepared as a pilot program for a larger computer and handles symmetrical reactors with core, side reflector and end reflectors, using 10 radial and 10 axial mesh regions. The output consists of the effective multiplication constant, the two flux distributions, and the fission source distribution. The extrapolated Liebmann process is used for the inner iterations.

Uranium and thorium beryllides and their solid solutions were prepared by reaction-sintering, reaction—pressing and arc—melting of mixed metal powders. The major difficulties of preparation were the large swellings accompanying reaction without pressure and the loss of beryllium at temperatures above 1200 — 1300ºC, the reaction—pressing method suffered least from these difficulties and yielded the purest and most dense products.

The heavy gas model using a synthetic kernel leads to coupled equations for the determination of the neutron flux in a bare reactor. The very special problem of solving analytically the defining equation for the energy dependent neutron flux in a region for which there are no source terms is considered. (auth)

Inhomogeneities in Brush UOX beryllium oxide observed in the powder and in cold pressed and sintered specimens have been removed by grinding the powder prior to fabrication, all grinding procedures reduced the densities obtained under standard sintering conditions, but some grain refinement was noted on sintering after short grinding periods. These effects are related to the introduction of alumina and silica impurities during ball milling. There is some indication that short grinding periods improve the strength of sintered specimens.

A self—abradory process is described for the small-scale preparation of 150 - 200 micron spheroidal particles of various UO2- ThO2 compositions. The particles can be sintered to high densities before or after dispersion in beryllium oxide. Because of the high compaction pressure used in making particles, they are strong enough to resist abrasion and crushing during mixing with beryllium oxide powder, after sintering, the particles consist of a (U, Th)02 solid solution with a small range of composition, but the overall composition does not vary from one particle to another. The types of porosity observed after sintering are consistent with the occurrence of two competitive mechanisms during spheroidisation, namely particle abrasion and particle build-up.

The 25% Cr, 20% Ni type stainless steel has been proposed for use in the Australian High Temperature Gas Cooled Reactor in core structures, and in hot gas ducting. Thus a knowledge of the compatibility of this steel with high pressure carbon dioxide was required. Rates and mechanisms of corrosion were investigated for machined, vapour blasted, and etched pretreated samples of this steel, exposed to carbon dioxide up to 3,000 hours in the temperature range 650 degrees C at gas pressures from 3 p.s.i.g. to 280 p.s.i.g. Oxide film flaking as apparent at all temperatures investigated but was only severe for pre-ground samples at 710 degrees C and above, and for pre-vapour blasted samples at 760 degrees C and above. However, severe intergranular penetration was observed in pre-etched samples on exposure to carbon dioxide at 650 degrees C and above. Pressure of the gas appeared to have no systematic effect on the corrosion rate, at least in the temperature range investigated. The maximum useful temperature for which the steel could be used would be limited by the amount of oxide flaking permissible. In reactor gas circuits where a small amount of scale flaking could be tolerated, the steel is satisfactory …

Fast neutron irradiation affects the properties of beryllium oxide by causing displacements and by causing nuclear transmutations. This report outlines the overall aims of a programmer to investigate this problem, reviews the information from overseas laboratories, and describes the results obtained to date at Lucas Heights. Results are given of measurements of properties of beryllium oxide fabricated by various methods and irradiated to doses of up to 7 x 10(20) avt (fission neutrons) at temperatures of 75 - 700 degrees C. The properties include macroexamination, dimensions, porosity, lattice parameter and line broadening, mechanical properties, thermal conductivity, metallography, and long wavelength neutron scattering. It is shown that an anisotropic lattice growth occurs which results in crumbling of the material at high doses. Fine-grained (<3 mu) materials withstands crumbling up to much higher doses than coase-grained material. The relationship between macroscopic growth, latttice growth, and the cracking and powdering is discussed in some detail and the results used to show the reasons for apparent discrepancies in data from overseas laboratories. Information relating to the defect structure is discussed and it is suggested that interstitial clusters in the basal planes are probably the cause of the marked anisotropy in the lattice growth. The …

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.

The main difficulties of experiments on the influence of radiation on creep is metals are discussed. Some typical apparatuses for investigation by using natural sources, reactors, cyclotrons, etc., are described. These methods have resulted in relatively inaccurate measurements up to now. Therefore, the published results do not allow any statement of laws, but only tendencies. There is a surprising influence of charged particles on creep rate in spite of their low depth of penetration. The discussion of the results leads to the conclusion, that the temperature of the specimen, the stresses and the density of beam are very important. Two requirements are put forward if such researches are to be of technical importance and not only of theoretical interest.

Selenenoyl-2-acetone is much more suitable for the extraction of thorium from aqueous solutions than acetylacetone, which is extensively used for this purpose. The stability constants of thorium selenenoyl-2-acetoneates and the distribution coefficient of the extracted complex in the CHCl3-H2O system have a higher value than those of the acetylacetonates of this element.

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.

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.

The complex formation reaction between beryllium and aluminon was investigated for different values of pH. It was established that at pH between 4 and 5 a complex is formed containing the constituents in the ratio 1 : 1 . At a pH between 7 and 8 a complex is formed having a beryllium-aluminon ratio of 3 : 1. At pH 6 both complexes are formed . It is shown that the complexes can be distinguished optically and in other aspects. The colorimetric determination of beryllium with aluminon is made at pH 5. At this pH value the results obtained for the determination of beryllium are satisfactory and of sufficient reproducibility.

1. The solubility of acetylacetone has been determined in an acetate buffer solution of ionic strength C.1 in relation to pH and temperature. 2. The distribution coefficients of acetylacetone have been determined between chloroform, carbon tetrachloride, benzene and an acetate buffer solution in relation to acetylacetone concentration and pH. 3. The relationship has been established between the rate at which indium acetylacetonate reaches partition equilibrium and the pH, initial acetylacetone concentration in the organic phase, and the different organic solvents. 4. The extent of the extraction of indiumacetylacetonate has been determined for three organic solvents at two acetylacetone concentrations in relation of pH. The independence of the degree of extraction from indium concentration was established in the region between 10(-4) to 10(-6) M. 5. 5. The indium acetylacetone compound was obtained by extraction from organic solvents. 6. The stability constants were calculated by two different methods for the uncharged complex and intermediate complexes; also the constants for the various steps of the dissociation of indiumacetylacetonate.

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.

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.

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.