THE DEVELOPMENT AND APPLICATION OF THE DISCRETE ORDINATES-TRANSFER MATRIX HYBRID METHOD FOR DETERMINISTIC STREAMING CALCULATIONS

Abstract

Integral transport theory is used to compute transfer matrix elements for neutral particle streaming through r-z rectangular voids. The transfer matrix is utilized in a hybrid method; it interfaces with a conventional discrete ordinates calculation outside the void. Since the hybrid interface is accomplished within the inner iteration of an existing discrete ordinates code, standard sweeping schemes used in SN codes are not adversely affected. The resulting transfer matrix is independent of the multigroup energy structure used in a calculation. Further, the transfer matrix is not affected by changes in materials or cross sections outside the void. For these reasons, once a transfer matrix is calculated it can be used in a wide variety of problems containing a similar void. In this study, the transfer matrix hybrid, standard discrete ordinates, and Monte Carlo methods are applied to two sample problems to compare the accuracy of these methods. The Monte Carlo results are considered correct in order to compute errors in the deterministic calculations. The transfer matrix hybrid method is more accurate than conventional SN methods; the ray effect, persistent in discrete ordinates calculations, is substantially reduced. In addition, the transfer matrix hybrid executes faster than higher order SN calculations.