On the cylindrical symmetry of neutron fluxes in square and hexagonal reactor cells

The accuracy of reactor cell calculations depends strongly on the used geometry modelling cells. To reach high precision, the actual cell geometries (square or hexagonal) should be used. Unfortunately, that requires at least two dimension calculations, which are more difficult to handle and are more time consuming. Often these actual cells are replaced by cylindrical ones in calculations. The main aim of this study is to determine the validity limit of the cylindrical fluxes symmetry in square and hexagonal cells to justify the cell cylindrisation. An extended iterative method is used to solve the integral transport equation within cells. Some improvements are obtained for the multiplication factor calculation.