Browsing by Author "Ramm, EJ"
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- ItemAn assessment of some organic binders for the fabrication of uranium dioxide fuel pellets(Australian Atomic Energy Commission, 1972-12) Ramm, EJ; Webb, CEUranium dioxide fuel pellets for water-cooled reactors are usually made by cold pressing and sintering UO2 powders with or without an organic binder. A wide range of binders was assessed and the most suitable was Cranco 253 (Poly-butylmethacrylate). Other binders such as polyvinyl alcohol, zinc stearate and Sterotex showed some promise, but further optimisation of their level and method of addition and of the debonding and sintering procedure is necessary.
- ItemA comparative study of two grades of BeO(Australian Atomic Energy Commission, 1961-11) Reeve, KD; Ramm, EJPechiney 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 strength falls due to increasing crystallite size. Cold—pressed and sintered Brush UOX appears weaker, possibly due to weaker grain boundary cohesion. Cold—pressed and sintered BeO is considered to be worthy of most intensive study as an irradiation resistant material, and suggestions are given for improving its strength and homogeneity and decreasing its crystallite size.
- ItemDevelopment and testing of corrosion-resistant alumina coatings for beryllia-based reactor fuel elements.(Australian Atomic Energy Commission, 1971-05) Reeve, KD; Ramm, EJ; Webb, CEThe use of beryllia as the basis of an all-ceramic fuel element for high-temperature reactors cooled by ambient air depends on inhibition of corrosion of beryllium oxide by protecting the surface of the fuel element. Alumina is a promising coating material. The development of corrosion resistant alumina coatings for BeO spheres is described, and results of corrosion, accelerated corrosion and neutron irradiation tests are presented. The limitations of the coating are discussed in detail Porous coatings can fail by 'undermining', but dense coatings are probably satisfactory for at least two years' operation out-of-pile at 1200ºC and for much longer times at lower temperatures. Satisfactory operation at 1200ºC for one year has been proved in a long term test. The eventual failure mechanism will probably be associated with the growth of a two layer reaction zone. Neutron irradiation tests indicate that a dose of 1020 nvt and possibly 1.6—2 x 102º nvt should be acceptable for retention of coating-to-BeO bond during simultaneous exposure above 500-700ºC to fast neutrons and moist air.
- ItemThe development and testing of Synroc C as a high level nuclear waste form(Cambridge University Press, 2011-02-15) Reeve, KD; Levins, DM; Ramm, EJ; Woolfrey, JL; Buykx, WJThe current status of SYNROC C research and development by the Australian Atomic Energy Commission is reviewed. A non-radioactive fabrication demonstration line designed to produce 10 cm o.d., 90 cm long, cylinders of SYNROC canned in stainless steel by the method of in-can hot pressing is being commissioned. Leach tests are proving the excellent leach resistance of SYNROC. Accelerated radiation damage testing using fast neutrons has simulated storage times of up to 6.7×105 years. Thermophysical properties of SYNROC have been measured over the temperature range 20–650°C. © Materials Research Society 1982
- ItemGrinding studies on beryllium oxide powder.(Australian Atomic Energy Commission, 1963-03) Reeve, KD; Ramm, EJInhomogeneities 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.
- ItemPreparation and evaluation of an ADU-derived ceramic grade UO2 powder(Australian Atomic Energy Commission, 1968-02) Ramm, EJ; Quaass, STThe method and equipment used to prepare a ceramic grade uranium dioxide powder are described, together with relevant characteristics of the intermediate and final products. The method chosen followed the well established ammonium diuranate route involving continuous precipitation from uranyl nitrate solution using gaseous ammonia. Conversion of the ammonium diuranate to uranium dioxide was effected by heating in a hydrogen/nitrogen atmosphere and following this with a low temperature stabilisation treatment. Various physical tests were carried out on the resultant powder, and finally, specimens were pressed and sintered over a wide range of pressures and temperatures. The tests indicated that the powder was 'sinterable' and that the method of preparation produced a ceramic grade powder exhibiting consistent properties and behaviour.