Abstract
Effect of cell simplification on cell average constants are evaluated by a Monte Carlo method in order to provide a simplified very high temperature reactor (VHTR) design method. First, the applicability of the Monte Carlo method to the present work is verified by the experiment analysis of the VHTR mock-up critical core. Then a technique to separate the volume and surface terms of resonance integral based on the Monte Carlo method is developed by introducing Marchuk theory. The percentage contributions to the resonance integral of the VHTR fuel assembly are 60% from the surface term and 40% from the volume term. Finally, due to simplification of the hexagonal SHE-14 cell to an annular cell with equal fuel volume, the K∞-value is enlarged by 0.8% Δk/k as the result of a 7% decrease of surface area, i.e. 0.7% increment of the resonance escape probability. The contributions of individual resonances of 235U and 238U to these terms are also discussed.
