Mechanical response of biological shielding ring to variations in azimuthal neutron flux distribution

The prolonged exposure of concrete to radiation affects significantly the concrete properties and consequently it influences the structural and shielding performance of the reactor shaft concrete structures. Therefore, the effect of neutron flux on concrete cannot be neglected. It is recommended to analyze the effect of neutron flux on the concrete ring as a three-dimensional problem, as important effects may be overlooked or misinterpreted when less dimensional approaches are adopted. The azimuthal flux distribution affects the results significantly, when the irregular load can cause much higher damage in comparison to the uniform load. There-fore, the arrangement of the fuel assemblies should be optimized not only with the objective to maximize the electric output but also to minimize the detrimental effect of the neutron flux on the biological shield structural elements. The regular inspections of reactors biological shield should be carried out after reaching the operating age of forty years in order to identify possible geometrical deviations. The effect of stress relaxation is neglected in this study and has to be added in the future. Relaxation can reduce significantly the stresses and the corresponding damage. Heating, which is associated with irradiation, is also neglected and has to be taken into consideration in future studies. The temperature expansion of the structural material caused by elevated temperature has to be added to the radiation-induced volumetric expansion