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The energy distribution of neutrons reflected from iron, soil, water, and polyethylene is measured with a monocrystal scintillation spectrometer for various angles of incidence of a beam of reactor neutrons at the surface of the medium being studied. The relationship is developed between the magnitude of the neutron albedo dose and the layer thickness for iron. The experimental data from this paper are compared with the results obtained by other authors.

where E (g) is the total collision cross section; d is the thickness of the layer. The particles remaining were assigned a weight [2s/E](1-P), where ~ is the scattering cross section. Histories were terminated when the particle weight became less than a given quantity, which usually was 0.1% of the penetration probability for unscattered radiation. The angutar neutron spectra outside a layer were obtained from a probability analysis over energy and direction of the neutrons escaping from the layer. The program wl~ch was made up in accordance with this scheme provided a determination of the coordinates of the point of neutron escape from the layer and atso output of data in the form of a 16-group energy spectrum for each of eight angular intervals (these intervals were selected with uniform steps in the cosine df th~ angle of calculations). For neutron energies g - 4 MeV, the statistical model of the nucleus was assumed valid, the excitation temperature of the nucleus being assumed to be T = 0.80 MeV [10], On the basis of experimental data in [11], corrections for direct interaction of neutrons with nucleons in the iron were introduced for E > 7 MeV. Results of the Monte-Carlo calculations were compared with multigroup calculations by the "transmission matrix" method in the 2P 7 approximation (ROZ program [2]). The angular and energy spectra from a plane, monodirectional source with the energy spectrum of a D--D source (Ema x = 3.4 MeV) outside a layer of iron 10 cm thick were calculated. The angular dependence of a given energy group was remarkably close in both cases, but some difference were observed in the relationship between groups, i.e., in the energy spectra. The Monte-Carlo calculation gave a softer spectrum. In the two cases, the maximum difference in the absolute number of neutrons escaping from tile layer in each group did not exceed 25%. Hence, it follows that the ROZ program, which requires considerably less machine time, can be used successfuUy in the one-dimensional case. In that case, it is expedient to monitor mass calculations with the ROZ program by periodic Monte-Carlo calculations. Note that the advantage in machine time increases with increasing thickness since the time used increases practically in proportion to attenuation in the Monte-Carlo method, and is proportional to thickness in the ROZ calculation.

We propose an algorithm for calculating ..gamma..-ray transmission, in particular the buildup factor, the integral albedo, and the absorbed and scattered energies scattering. The algorithm can be implemented with small computers and enables one to perform a general analysis in a few minutes, where a single universal program can be used for the engineering examination of numerous different forms. The algorithm is based on transferring from the exact solution of the one-dimensional radiation transport equation to the three-dimensional one.