Thermal neutron diffusion parameters of heavy water

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The decay of the asymptotic thermal neutron distribution was measured by the pulsed technique in D 20(99·82 mol per cent, δ = 22°C) within a rather large range of geometrical buckling (00013 cm −2 < B 2 < 0·0470 cm −2). In the lower buckling region (B 2 < 0·0060 cm −2) we employed a modal analysis method outlined in a previous paper ( Meister, 1963). From the experimental decay constant α plotted against B 2 we obtained the diffusion constant D 0 = (2000 ± 0·0009) × 105 cm 2/sec and the diffusion cooling constant C = (525 ± 025) × 105 cm 4/sec in a fairly good agreement with earlier experimental data ( Sjöstrand, 1958; Ganguly and Waltner, 1961; Waltner and Westfall, 1962).