Browsing by Author "Dalton, AW"

Now showing 1 - 9 of 9
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    Absolute measurement of the responses of small lithium glass scintillators to gamma radiation
    (Australian Atomic Energy Commission, 1987-04) Dalton, AW
    The absolute scintillation efficiency and intrinsic resolution of lithium glass scintillators for electron excitation have been determined over a range of electron energies lithium concentrations and lithium enrichments. Measurements of these response characteristics form part of a study on the possible use of such glasses for the determination of tritium breeding in fusion reactor blanket experiments. The measurements were undertaken to establish a basis for extracting the information relating to tritium production reactions from the background signals induced within the glass scintillators by the neutron/gamma fields of a fusion reactor blanket. Criteria for the selection of glasses most suitable for tritium breeding measurements are discussed in tems of their observed responses.
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    Calculation of power transients for the SPERT II nuclear reactor core with inclusion of nucleate boiling of the coolant
    (Australian Atomic Energy Commission, 1983-02) Dalton, AW
    The published data for a series of power transients initiated in the water-cooled core of the SPERT II nuclear reactor were investigated to determine the magnitude of the reactivity feedback effects arising from heat transfer and vapour void formation during subcooled nucleate boiling. This was done using the NAIADQ computer code which describes the thermohydraulic behaviour of the water coolant in the fuelled region of the core in terms of a set of one-dimensional linear finite difference equations. Nucleate boiling at the fuel surface is represented as an expanding superheated layer of water in which saturated vapour is assumed to be uniformly generated at a non-equilibrium rate. The simulation of the transients all of which were initiated at ambient temperature necessitated the calculation of heat transfer from the fuel to the water coolant in the regimes of conduction convection and surface boiling for a wide range of coolant flow rates during rapidly changing reactor power levels. The calculated variations in the reactor power with time during the transients are in good agreement with the measured data over the range of conditions tested in the experimental investigations.
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    Measurement of the responses of small lithium glass scintillators to protons, deuterons and alpha particles
    (Australian Atomic Energy Commission, 1987-01) Dalton, AW
    The application of lithium glass detectors to the measurement of the tritium production rate distribution in fusion blanket assemblies is under investigation at Lucas Heights. As a consequence of neutron-induced reactions within the glass detector many charged particles are produced with energies ranging from zero to about 20 MeV all of which produce scintillations. To isolate the signals arising from the tritium production reactions 6 Li(nα)T and 7 Li(n,n'α)T within the glass the characteristic responses of the glass to all charged particles are required. As part of this investigation the response characteristics of thin lithium glass scintillators to protons deuterons and alphas have been measured as a function of particle energy (0.8 to 2.7 MeV) lithium concentration (2.4 to 8.3 wt %) and lithium enrichment (95 wt % 6 Li to 99.99 wt % s7 Li).
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    NAIADQ, a computer program for calculating reactivity transients in low power experimental water reactors.
    (Australian Atomic Energy Commission, 1983-04) Dalton, AW
    The computer code NAIADQ is designed to simulate the course and consequences of non-destructive reactivity accidents in low power experimental water-cooled reactor cores fuelled with metal plate elements. It is a coupled neutron kinetics-hydrodynamics-heat transfer code which uses point kinetics and one-dimensional thermohydraulic equations. Nucleate boiling which occurs at the fuel surface during transients is modelled by the growth of a superheated layer of water in which vapour is generated at a non-equilibrium rate. It is assumed that this vapour is formed at its saturation temperature and that it mixes homogeneously with the water in this layer. The code is written in FORTRAN IV and has been programmed to run as a catalogued procedure on an IBM operating system such as MVT or MVS with facility for the inclusion of user routines.
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    Preliminary survey of requirements for heavy water moderated reactor lattice experiments in the proposed critical facility
    (Australian Atomic Energy Commission, 1968-02) Dalton, AW; McCulloch, DB
    Calculations have been carried out to assess the fuel and control requirements for lattice measurements in heavy water moderated reactor cells, using a 'split-table' type machine with a U235/graphite driver region. The METHUSELAH code was used to calculate cell-averaged cross-section data for the heavy-water moderated region, and GYMEA for the U235/graphite driver region and the graphite reflector. CRAM calculations in four groups were then made for critical configurations in a range of driver region compositions and assembly geometries. It was established that for the type of natural uranium steam-generating heavy water reactor lattice considered, an adequately close approximation to the equilibrium neutron spectrum for the critical SGHWR could be established over a 30cm radius at the centre of the assembly, using approximately one tonne of SGHWR type fuel, 9 kg U235 and 13 tonnes of graphite. The latter two quantities would be somewhat increased if practical packing densities for the machine were taken into account. Adequate reactivity control for operation is available by use of a practicably small number (about 5) of conveniently sized plates 'black' to thermal neutrons.
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    Prompt nubar measurements for thermal neutron fission.
    (Australian Atomic Energy Commission, 1967-03) Boldeman, JW; Dalton, AW
    The number of prompt neutrons (v) produced in the thermal neutron induced fission of U233, U235, Pu239, andPu24l has been determined with high accuracy using the liquid scintillator technique- Measurements were made relative to an assumed value of v = 3.784 for the spontaneous fission of Cf252. The present results are compared with previous measurements.
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    Theoretical investigation of absolute neutron detection
    (Australian Atomic Energy Commission, 1967-09) Dalton, AW; Lam, KS
    A survey was made of the detection systems classified as 'flat response' in order to establish their use in high accuracy measurements of absolute neutron intensities for a wide range of neutron sources. Two detection systems involving neutron moderation in either graphite of an hydrogenous material were selected as having the most suitable characteristics. Numerical solutions of the neutron transport equations for these systems were computed to determine the conditions required to produce minimum variation of efficiency with energy. It was shown that, with the suitable choice of moderator composition and size, it should be possible to reduce these errors to less than one per cent over the energy range 100 eV to 4 MeV.
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    Tritium breeding experiments in a fusion blanket assembly using a low-intensity neutron generator
    (Australian Atomic Energy Commission, 1987-01) Dalton, AW; Woodley, HJ; McGregor, BJ
    Experiments have been carried out to determine the accuracy with which tritium production rates (TPRs) can be measured in a fusion blanket assembly of non-spherical geometry by a non-central low intensity D-T neutron source. The tritium production was determined for samples of lithium carbonate containing high enrichments of 6 Li(96%) and 7 Li(99.9%). The measured data were used to check the accuracy with which the TPRs could be numerically predicted using current nuclear data and calculational methods. The numerical predictions from tritium production from the 7 Li samples agreed within the experimental errors of the measurements but 6 Li measurements which differ by more than 20 per cent from the predicted values which were observed in the lower half of the assembly.
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    Variation of neutron yield from a titanium-tritide target during deuterium beam bombardment
    (Australian Atomic Energy Commission, 1986-05) Dalton, AW; Woodley, HJ
    In the laboratory simulation of D-T fusion breeder blankets 14 MeV neutrons are produced by the bombardment of a titanium-tritide target with deuterium ions using accelerating voltages up to 500 keV and beam currents ranging from micro to milliamperes. For the accurate determination of tritium breeding ratios in the experimental assemblies an absolute determination of the total neutron yield over the irradiation period is required. The theoretical and experimental methods used to determine the ion composition of the deuterium beam the changing absolute yields and energy distributions of the neutrons emitted from the target during prolonged irradiation are described using the AAEC 14 MeV neutron generator as a typical example. Analysis of the measured data identified two ion species in the beam of the neutron generator. It was shown that after a 21-hour irradiation of the target with a 250 mu A beam (18.5C) at 200 kV the neutron output from the D-T reaction dropped from an initial value of 2 x 10 1 0 to 4 x 10 8 neutrons per second. The integrated neutron output over this period was estimated to be 2.05 x 10 14 of which about 24 per cent originated from the interaction of monatomic ions and 75 per cent from diatomic ions; less than one per cent arose from D-D reaction.