Abstract
The improved coarse mesh method, which was originally derived by Askew and applied to fast reactor core calculations by one of the authors, has been applied to boiling water reactor core calculations. Since direct application of the method leads to negative fluxes in the reflector region, a procedure has been developed in which the correction factor for coarse meshes is not utilized in the reflector. The results of the improved coarse mesh calculations were compared with those of fine mesh calculations. The negative fluxes were eliminated and good agreement was obtained for the neutron multiplication factor and power distributions in fuel assemblies near control rods, though the accuracy of power distributions near the reflector was as that of conventional coarse mesh calculations.
