Browsing by Author "Spinks, N"

Now showing 1 - 6 of 6
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    Analysis of flow stability in boiling systems with the TOSCLE code
    (Australian Atomic Energy Commission, 1971-05) Spinks, N
    Two-phase-flow stability can be analysed with the TOSCLE code. TOSCLE uses equations derived by linearising and taking Laplace transformations of the mass, energy and momentum conservation equations and solving the resultant one-space-dimension equations analytically along a straight, uniform cross-section pipe with uniform heat addition or removal per unit length. Separate solutions are obtained for single-phase regions and two-phase regions of the pipe. Single-phase regions can be either subcooled liquid or superheated vapour. Complicated circuits can be analysed by subdividing the components until they conform to the "straight, uniform cross-section, uniform heat" description. The code calculates steady-state pressure drop for given inlet velocity, then perturbed pressure drop for given inlet velocity perturbation. The latter calculation is repeated at a number of frequencies to permit the drawing of a Nyquist plot of the inlet velocity to pressure drop transfer function from which stability is assessed. A simple slip correlation is incorporated as well as a two-phase-friction multiplier, which is taken as a quadratic in quality. Localised restrictions are permitted. The deficiencies of the analysis are a neglect of subcooled boiling and of variations in fluid saturation properties with pressure. The assumption of uniform power requires more subdivision of the circuit than would otherwise be necessary and the simple slip correlation is inaccurate near unit void fraction.
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    DIFF, a code to prepare neutron diffusion theory parameters from the results of the code WDSN.
    (Australian Atomic Energy Commission, 1967-03) Spinks, N; Manning, G
    With a solution of the multigroup neutron transport equation available for a problem in one dimensional geometry, diffusion theory parameters are determined so as to reproduce in diffusion theory the essential characteristics of the transport solution. Calculation of a more realistic reactor configuration can then be attempted in diffusion theory. Diffusion coefficients, taken as constant within a uniform region, can be determined so that the diffusion flux is an optimum fit to the transport flux. As an option the conventional 1/3Σtr can be used. The homogeneous boundary condition is found from a diffusion theory calculation which uses the transport net current as an inhomogeneous boundary condition. The homogeneous boundary condition forces the diffusion theory to reproduce exactly the transport leakage and multiplication constant. A discontinuity in the diffusion flux is permitted at interfaces between different materials. Interface conditions, if applied, guarantee that any reaction rate, integrated over the volume of a uniform region, is preserved by the diffusion theory. The DIFF code uses the results of the WDSN transport code to calculate diffusion theory parameters for the CRAM diffusion code.
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    A method for calculating the reactivity worth of partially inserted control rods using two-dimensional geometry
    (Australian Atomic Energy Commission, 1965-04) Spinks, N
    The three dimensional problem of a reactor with partially inserted control rods is reduced to a two dimensional problem by a redistribution of control material within the reactor. The transformation is exact when the pitch circle radius of the rods and the depth of insertion of the rods into the reactor are large compared with the control rod pitch. The effect of variations in pitch on the accuracy of the transformation is investigated by calculation.
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    Reactivity worth of control rods in the beryllium oxide moderated pebble bed reactor
    (Australian Atomic Energy Commission, 1967-02) Spinks, N
    Preliminary and final studies are reported for the worth of tubular control rods in a beryllium oxide moderated pebble bed reactor system. In the preliminary study the consideration of ball flow forces the investigation of a number of control rod arrangements. In addition, a range of rod sizes is considered. In the final study a particular rod size and pattern is chosen for more detailed investigation. For the intermediate reactor cores under consideration the control rods must absorb appreciably in the KeV region. A feature of the final study is the accurate way the epithermal absorption can be taken into account while using a three group model in the reflected reactor. The preliminary study is not so accurate but is useful for comparative purposes.
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    TWIST - a numerical technique for calculating the steady-state mass fraction variation in an axi-symmetric binary gas mixture subjected to pressure gradients
    (Australian Atomic Energy Commission, 1973-04) Spinks, N; Wilson, DJ
    The equation for diffusion in a binary gas mixture is integrated over each of a number of elements into which the R-Z system volume is divided. The resulting equations are soluble using the TWIST programme to give the mass fraction variation through the system. The Programme is suitable for analysis of any device which utilises pressure diffusion for the separation of a binary gas mixture, the components of which have approximately equal molecular weights and is describable in the R-Z coordinate system. Applications include the centrifuge, the vortex tube and the Vortex Matrix. A knowledge of the mixture mass flow and pressure distribution throughout the system is assumed. A weakness of this method is the requirement of a fine subdivision of the system volume when such flows are large. The TWIST programme has been applied to a counter-current centrifuge and the results compared with those from Cohen's theory.
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    Worth of boron rod in the reactor MOATA
    (Australian Atomic Energy Commission, 1967-06) Spinks, N
    The U235 fuel increase required to compensate for the insertion in MOATA of an enriched boron rod is measured. The DIFF code is used to calculate the mass increase and comparison with the experimental result provides a check on the theory incorporated in the code. In addition to the experimental check, a simplified calculational mock-up of the experiment is used as the basis of a more detailed comparison between the diffusion theory and transport theory. The worth of the rod as calculated by the diffusion theory is high by 10 per cent when compared to experiment and low by about 3 per cent when compared to transport theory. In general, the neutron fluxes calculated by the diffusion theory agree to within 2 per cent with those from transport theory.