Measurement of the slowing down time to 0.3 eV in beryllium oxide.
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Date
1970-07
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Publisher
Australian Atomic Energy Commission
Abstract
The reaction rates of plutonium-239 and boron (1/v) were measured as a function of space and time in a large block of beryllium oxide following the injection of a pulse of fast neutrons. The time-dependent reaction rates associated with the various Fourier spatial modes were derived from the experimental results. The experimental value of the peaking time of the plutonium-239 reaction rate associated with the fundamental spatial mode was found to be 19.85 + 1.1 μ sec. A theoretical value of 16.5 μ sec was obtained using a time-dependent zero-dimensional diffusion code and a crystal scattering kernel for beryllium oxide. It is in marked disagreement with the experimental value. Measurements made of the time to peak in the plutonium-239 reaction rate as a function of distance from the source showed a total variation of a 4 μ sec in peaking time over a distance of 53 cm. Theoretical calculations of the peaking time as a function of distance showed a similar variation and the general trends were in good agreement with the experimental result. There was, however, a constant discrepancy between the theoretical and experimental results of the order of that noted for the fundamental mode.
Description
Keywords
Beryllium oxides, Plutonium, Boron, Fast neutrons, Spatial distribution
Citation
Rainbow, M. T., & Ritchie, A. I. M. (1970). Measurement of the slowing down time to 0.3 eV in beryllium oxide. (AAEC/EM548). Lucas Heights, NSW: Australian Atomic Energy Commission.