Browsing by Author "Hickman, BS"

Now showing 1 - 15 of 15
  • Thumbnail Image
    Item
    Analytical description of growth of beryllium oxide during neutron irradiation
    (Australian Atomic Energy Commission, 1966-04) Pryor, AW; Hickman, BS
    A simple analytical model is developed which adequately describes the available data on the lattice and macroscopic growth of beryllium oxide under neutron irradiation. This model is then used for interpolation and extrapolation of existing data,, The model has a large number of adjustable parameters and it is emphasised that it does not necessarily bear any direct relation to the actual defect structure.
  • Thumbnail Image
    Item
    Effect of irradiation on the mechanical properties of beryllium metal.
    (Australian Atomic Energy Commission, 1965-01) Stevens, GT; Hickman, BS
    Results are presented of mechanical property measurements on beryllium metal irradiated up to 6 x 1020 nvt > 1 MeV at 75 - 100ºC and 3.2 x 1020 nvt at 550ºC. The property changes are interpreted in terms of helium distribution in the material.
  • Thumbnail Image
    Item
    The effect of neutron irradiation on beryllium metal.
    (Australian Atomic Energy Commission, 1963-06) Hickman, BS; Stevens, GT
    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 irradiation temperatures below 500ºC, particularly in the range 300 — 500ºC, it is concluded that nucleation of gas bubbles at precipitate particles is the only satisfactory explanation of the wide variations in behaviour of beryllium metal fabricated by various methods.
  • Thumbnail Image
    Item
    The effect of neutron irradiation on beryllium oxide
    (Australian Atomic Energy Commission, 1962-10) Hickman, BS
    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 programme 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 nvt (fission neutrons) at temperatures of 75 — 700ºC. 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. The damage rate is much smaller for irradiation at 500 — 700ºC than for equivalent doses at 100ºC. Fine—grained (<3/μ) material withstands crumbling up to much higher doses than coarse—grained material. The relationship between macroscopic growth, lattice 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 effect of neutron energy spectrum on the damage rate is discussed and finally the potential of beryllium oxide as a reactor material is assessed. It is concluded that very fine grained material should withstand doses of at least 1— 2 x 10 21 nvt at temperatures of 500 — 1000ºC without serious deterioration of properties. More information, particularly on changes of mechanical properties and thermal conductivity, is required to confirm this conclusion and to ascertain whether the material will withstand higher doses.
  • Thumbnail Image
    Item
    Effects of irradiation on beryllia-based fuels.
    (Australian Atomic Energy Commission, 1967-09) Hickman, BS; Rotsey, WB; Hilditch, RJ; Veevers, K
    Dispersions of (UTh)O2 in beryliia, containing 1.7 per cent to 25 per cent (UTh)C>2 in three fuel particle sizes, coarse (150 —200μ)> medium (33 — 35μ and fine (<10 and <5º) were irradiated to burnups of 3—10 per cent of heavy metal atoms in the range 300-900ºC, in both fast and thermal fluxes. Changes in volume, lattice parameter, line breadth, and modulus of rupture were measured. Volume changes in the fine dispersions were ascribed wholly to fission fragment damage and were about 50 per cent greater than those caused by fast neutrons alone; they increased with increasing fission fragment flux, and decreased as irradiation temperature increased. Volume changes in medium and coarse dispersions were about 25 per cent greater than those caused by fast neutrons alone; the enhancement of the damage is attributed to the additional β flux. As fuel particle size increased, deterioration in strength under irradiation was more marked. This was attributed to more intense fission fragment damage in the recoil zone around larger particles causing volume increases which exceeded those of the remainder of the matrix. For maximum initial strength and retention of strength under irradiation the fuel particle size should not exceed 5μ, and the inter-particle spacing should not exceed 30.
  • Thumbnail Image
    Item
    Escape of fission products from slurry particles
    (Australian Atomic Energy Commission, 1956-02) Hickman, BS
    The escape of fission products from fissile particles by recoil and by diffusion are discussed in general terms and equations governing these processes are derived. Experimental determinations of the mean free paths of the fission fragments and of the diffusion coefficients are reviewed. This data is then applied to a slurry of the composition under consideration viz. 1 or 2 atomic percent uranium, as metal or oxide in sodium. Tentative conclusions are drawn as to the optimum size for the slurry particles.
  • Thumbnail Image
    Item
    Examination of BeO irradiated at elevated temperatures in the engineering test reactor
    (Australian Atomic Energy Commission, 1964-09) Hickman, BS; Chute, JH
    A description is given of an examination of BeO samples irradiated by the General Electric Co. in the Engineering Test Reactor, Idaho Fails, to doses up to 1.2 x 1021(> 1 MeV) and temperatures in the range 470 — 1200ºC, at dose rates of 1 to 3 x 1014 nv. The results of X—ray measurements and optical and electron microscopy are presented and discussed. Comparisons are made with previously reported results on similar material irradiated in the reactor HIFAR at lower dose rates.
  • Thumbnail Image
    Item
    H.T.G.C. fuel and moderator material irradiation programme.
    (Australian Atomic Energy Commission., 1958-01) Hickman, BS
    Probable mechanisms of irradiation damage in fuel and moderating materials of interest to the H.T.G.C. Reactor programme are discussed. A programme is outlined for investigations into irradiation damage in H.T.G.C. fuels and moderators. The experimental methods to be used are briefly outlined.
  • Thumbnail Image
    Item
    The irradiation behaviour of beryllium based dispersion fuels - a preliminary irradiation experiment.
    (Australian Atomic Energy Commission, 1962-09) Hanna, GL; Hickman, BS; Hilditch, RJ
    The effects of fission fragment damage on vacuum hot pressed fuel specimens of (U Th) Be13 dispersed in a beryllium matrix were examined by irradiation in a predominantly thermal neutron flux. Damage equivalent to that caused by 4 x 10 19 to 11 x 10 19 fissions per cm3 (depending on specimen composition) was achieved at temperatures between 435º and 530ºC. 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 per cent. — was due to thermal effects alone. Release of fission gases was as high as 2 per cent, in some cases and was generally higher than would be expected from recoil in specimens having no 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 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 porosity.
  • Thumbnail Image
    Item
    The irradiation behaviour of beryllium oxide dispersion fuels.
    (Australian Atomic Energy Commission, 1963-03) Hanna, GL; Hickman, BS; Hilditch, RJ
    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 were higher in the latter specimens.
  • Thumbnail Image
    Item
    The irradiation behaviour of hot-pressed dispersions of (U,Th)Be13 in beryllium - second irradiation experiment.
    (Australian Atomic Energy Commission, 1963-11) Hanna, GL; Hickman, BS; Hilditch, RJ
    Fuel specimens having uranium—thorium beryHides as the fissile bearing phase were irradiated at 400 to 700 ºC to burn—ups between 7 and lla/0 uranium in a predominantly thermal flux, two specimens of massive (U.;Th)Be 13 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 cent0 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) Be 13— Be dispersions prepared by other techniques.
  • Thumbnail Image
    Item
    Irradiation of beryllium at elevated temperatures. Part II irradiation of RIG X-74 in HIFAR
    (Australian Nuclear Science and Technology Organisation, 1963-12) Hickman, BS; Bannister, G
    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.
  • Thumbnail Image
    Item
    Irradiation of uranium metal tubes and rods in a 4V hole in HIFAR
    (Australian Atomic Energy Commission, 1961-10) Hickman, BS; Smith, R; Hilditch, RJ; Mercer, WL
    This report covers all aspects of the irradiation and post-irradiation examination of the specimens in the first test of metallic G.E.G.B. uranium in the HIFAR materials testing reactor. A preliminary report (NPCC/FEWP/P.667) issued in February, 1961, gave the results of the initial measurements and visual inspection of the specimens. The earlier report divided the specimens into three main groups into which they appeared to fall conveniently at the time. Further detailed examination, including a large amount of metallographic study, has suggested that it is better to divide the specimens into four groups with groups 1 and 2 including all results of direct application to power reactor fuel element operation. Certain sections of the present report repeat some of the information already given in the preliminary report. This Material has been unclassified
  • Thumbnail Image
    Item
    Post-irradiation facilities at Lucas Heights
    (Australian Atomic Energy Commission, 1959-04) Ebeling, DR; Hickman, BS
    The post irradiation facilities at present under construction at Lucas Heights are described, and the equipment which will be available; these facilities are discussed.
  • Thumbnail Image
    Item
    The relationship between microcracking and mechanical properties in neutron-irradiated beryllium oxide
    (Australian Atomic Energy Commission, 1964-08) Hanna, GL; Stevens, GT; Hickman, BS
    Beryllium oxide bend test specimens of two grain sizes, 1—2 microns and 8—35 microns, were irradiated to fast neutron doses of up to 5 .6 x 1020 nvt (above 1 MeV) at 75 — 100ºC. Specimens were examined by X—ray line breadth (30.0 reflection), modulus of rupture, elastic modulus, open porosity, and lattice parameter measurements. The results show that there is no significant change in mechanical properties up to the dose at which microcracking is first observed i.e. .5 x 1020 nvt in the case of the fine grain size material and 1.2 x 1020 nvt in the case of the coarse grain size material. Above these doses the modulus of rupture and the apparent elastic constants fall rapidly. Microcracking occurred at an earlier dose in both materials than would have been expected from earlier work.