Narrow-duct-streaming calculations using generalized configuration factorswithin the discrete ordinates method

In calculating neutral particle transport through elongated voids with the discrete ordinates method, the problem of ray effect may occur if standard angular quadrature sets are used. To mitigate this ray effect, the configur ation-factor concept developed in the theory of thermal radiation for calcu lating the radiation exchange among surfaces is applied here. The common co nfiguration;factor concept is extended in such a way that the angular depen dence of the radiation emitted from the surfaces can be considered. The met hod is applied to regular and annular cylinders with r-z geometry and incor porated into a two-dimensional discrete ordinates transport code. Calculati ons on a narrow-duct-streaming problem show that the ray effect is strongly reduced by this method. The new method gives results equivalent to or even better than a standard discrete ordinates calculation using a biased angul ar quadrature set with 166 directions at computing times for one inner iter ation that are about a factor of 2 less.