Characteristics of Discrete Sn Calculation for Angular Distribution and Scalar Flux of Neutrons Penetrating through Media

概要

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The significant discrepancies often observed between the discrete Sn calculations and the measurements of the angular flux spectrum of neutrons at an angle of 0° have been studied for the benefit of analyses of time-of-flight measurements. Examination of the uncollided angular flux and scalar flux distribution yielded information on the relation between the accuracies obtainable in the calculations and the order of quadrature set used therein. Predictions on the angular flux in graphite resulting from the use of S16, S32 and S48 quadratures, and on the scalar flux in water from the S16 quadrature were compared with the results of measurements and of PALLAS transport calculations. It was found as a result that the S48 quadrature is most suitable for analyzing the 0° angular flux spectrum of the time-of-flight measurements, and that the S16 quadrature is sufficient for scalar neutron flux calculations for reactor shields. The spurious fluctuations observed in the ANISN angular distributions are not due to insuffici-ency in the number of iterations in computation, but to the coarseness of the spatial intervals used.
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