Monte Carlo Investigation of Experimental Setup for Reactor Neutron Source

Abstract

The prediction of integral parameters in the nuclear installations (fluence, activities, doses, etc.) requires a reliable theoretical modelling. The modelling includes the used transport codes themselves as well as reliable nuclear data such as microscopic nuclear parameters, cross sections, covariance matrices, etc. To verify the performed calculations, suitable experiments are used. On the other hand, one may use the theoretical modelling in order to evaluate the most suitable setup for performing a reliable experiment. This is of distinct importance when neutron activation is in place, since the neutron flux, angle of excitation and energy here is of particular importance. Using preliminary modelling the of response function in the activated materials a lot of time and capacity can be saved during the experimental process. This is of particular importance when investigate the 93mNb isotope since it has important properties in the state-of-the-art activity measurement techniques investigations, due to its low-energy gamma lines and its high level of masking due to other elements, and especially the tantalum. Niobium and tantalum are chemical “twins” of the vanadium triad of the periodic table and are notoriously difficult to separate from one another and from their naturally occurring ores, due to their near-identical physical and chemical properties. That is why 93mNb is suitable for a test element in the development of principally new approaches in the radiochemistry. The neutron source definition for Monte Carlo calculations for Nb, Fe and Cu foils activation is described in the paper. The reactor neutron source geometry model is presented. Results for the neutron fluence for activation of the investigated elements are obtained in radial and axial directions of the experimental setup area. Suitable positions for the placement of the investigated elements are selected. The obtained results provide a reliable basis for performing neutron activation experiments for technogenic radionuclides important for man and environment.