Resonance Absorption in High-Temperature Gas-Cooled Reactor Fuel with Double Heterogeneity

A simplified method based on the intermediate resonance approximation is proposed to deal with the double heterogeneity encountered in design calculations of high-temperature gas-cooled reactors. First, a fuel rod with grain structure is homogenized by introducing an equivalent homogeneous material, in the form of an intermediate resonance approximation, that contains a fictitious moderator substituted for both the grain heterogeneity and the scattering in moderator region. Second, the cluster configuration of the homogenized rods is treated by use of the fictitious moderator. This method is shown to offer a convenient and simple means with good accuracy and short computing time when combined with the “table look-up” method of resonance shielding factors.