Dose Equivalent Rate Evaluation for Nuclear Reactors Shielding Studies by Means of the Point Kernel Technique

A shield is a physical entity interposed between a source of ionizing radiation and an object to be protected such that the radiation level at the position of the object will be reduced. The term shielding refers to a system of shields assembled together. In nuclear reactor applications the radiations involved are fast and thermal neutron and gamma radiation (primary or secondary whether originated directly from the core or from neutron capture) . The dose equivalent rate to the target is given by the summation of the dose equivalent rate of each radiation component, which can be determined from the related radiation flux. As the Transport Equation requires substantial computational resources, simplified methods-such as the point kernel technique- have been developed for radiation flux calculation across shielding. In this work, the reliability of the point kernel technique for nuclear reactors radiation fields has been tested. Case studies regard three main types of nuclear reactors: Bulk Shielding Reactor, Light Water Reactor and Fast Breeder Reactor. In all cases, the point kernel overestimates radiation fluxes, and thus the dose equivalent rate, which turns to radiation protection safety purposes. Moreover, some observations have been drawn about the effectiveness of the proposed shielding in reducing the dose equivalent rate to the target to predefined limits, also according to the prevalent radiation type.