An improved homogenization technique for pin-by-pin diffusion calculations

An alternative approach for cell homogenization aimed for pin-by-pin diffusion calculations is presented. This approach consists of adding degrees of freedom to the homogenized problem by introducing a weakly space-dependent diffusion coefficient. This allows for improved preservation of averaged group reaction rates, surface currents and system eigenvalue compared to traditional pin-by-pin homogenization methods, such as FVW or SPH. An iterative application of this approach, called the iterative semi-homogenization method (ISH), is presented and is evaluated and compared to other homogenization methods using a set of one dimensional, one-group test problems. According to the set of test problems used, the ISH is found to be highly successful in preserving reaction rates and surface currents, outperforming the FVW and SPH methods. As for the preservation of the system eigenvalue, the ISH shows good results in comparison to the FVW method.

► We suggest an alternative approach for pin-by-pin homogenization. ► We introduce a discretely–spatially-dependent diffusion coefficient. ► The suggested method outperforms traditional methods in preserving reaction rates and surface currents. ► The suggested method shows an advantage in predicting neutron flux shape.