Miniature Neutron Source Research Articles

Design of an out-of-tank neutron beam line for prompt gamma neutron activation analysis at low-power Miniature Neutron Source Reactor

Research reactors are strong and stable neutrons sources, and various researches and applications were carried out using their neutron and gamma beamlines. Some research reactors, such as Miniature Neutron Source (MNSR) Reactors, do not have beam tube in their original design, which can be considered as a disadvantage. The design and installation of beamlines can develop their applications. In this research, the design and optimization of a suitable neutron beamline for PGNAA is done at Isfahan MNSR. Designs are done to reach the appropriate neutron beam parameters and taking into account the geometrical limitations of the MNSR. Neutron beam parameters including thermal neutron flux, thermal to total neutron flux, and thermal neutron flux to gamma dose ratio are considered. For this, vertical beamlines with different diameters are simulated and the optimal diameter is determined. Also, for optimization of beam parameters, a thermal column and gamma filter are considered and optimal conditions are determined.

Activation Constants for Slowpoke and MNS Reactors Calculated from the Neutron Spectrum and k0 and Q0 Values

The relative thermal, epithermal and fast neutron fluxes were measured in the inner and outer irradiation sites of three Slowpoke reactors and one Miniature Neutron Source (MNS) reactor by the bare triple monitor method. Using the measured neutron spectrum parameters and a compilation of published k0 and Q0 values, activation constants were calculated for the most intense gamma-rays of all nuclides commonly used in NAA. The resulting table of constants can be used to standardize NAA measurements for all elements when combined with relative efficiency measurements and the measurement of the thermal neutron flux with one standard. The observed constancy of the neutron spectra suggests that these activation constants are valid for all 14 Slowpoke and MNS reactors.