In this work, colemanite, a boron-bearing ore, was added to ordinary Portland concrete as aggregate. Some concrete blocks containing different amounts of colemanite were produced and their neutron permeability and compressive strength were determined. From the results of the experiments, taking into account the nuclear and structural properties of shielding material, a proper colemanite adding ratio was presented. A neutron transport calculation of the shield containing colemanite was made by using the removal-diffusion technique and the decrease in shield thickness, compared to ordinary Portland concrete, was found. Assuming a 20-year stepwise irradiation, the neutron-induced activity within the shield was calculated. Cooling time after shutdown was taken up to 10(5) years. By comparing the total and elemental activities of the ordinary and colemanite-added Portland concretes, the contribution of colemanite to the shield activity was investigated.