APPLICATION OF THE MULTIGROUP C_N METHOD TO THE CALCULATION OF THE ALBEDO OF A SEMI-INFINITE MEDIUM

摘要

The C_N method of solving the transport equation has been developed at Saclay, to solve different problems in one-velocity theory. In this work, the C_N method (Kavenoky, A., 1978), is applied to multigroup problems in plane geometry. Its main advantage is that the computing time is independent of the media considered, because the space variable does not appear explicitly, this method is based on a Lemma proved by Placzek (Case et al., 1953). An integral equation is provided for the angular flux at the boundaries of the various media. The purpose of our work, is to calculate the albedo of an absorbing and scattering half-space, in a multigroup scheme with an anisotropic scattering law. As an extension of this work, the albedo and the transmission ofa slab may also be calculated. It is also planned to use the method for the calculations of the albedo of a pressurised water reactor (PWR) reflector and of the fluence of a PWR tank. First the multigroup C_N method is applied to the calculations of thealbedo betagg', i.e. the spectrum of neutrons reflected from a scattering and absorbing half-space by a neutron entering this half-space, either according to a mu~n or to a collimated incoming flux. The scattering anisotropy is taken into account by Legendre polynomial.