Известия Томского политехнического университета: Инжиниринг георесурсов (Sep 2017)
Calculated determination of corrections for resonance self-shielding of activation gold/tantalum detectors at irradiation
Abstract
The relevance of the discussed issue is caused by the need to evaluate the self-shielding factors in activation gold/tantalum indicators used while conducting Instrumental Neutron Activation Analysis by single-limit comparative method of k0-standartization. At irradiation of activation indicators the flux perturbation occurs due to neutrons absorption inside of the indicator material in the field of epithermal neutron nuclear reactor. This effect may have a great importance especially if indicator materials had resonances in this energy range. The self-shielding factor (Gres) should be considered at activation for taking into account the effect of the neutron flux perturbation. This factor depends on geometry and sample size as well as on physical and nuclear properties of isotope. The authors have proposed the curve, which agrees well with the experimental and the calculated values. The main aim of the studyis to identify the corrections on self-shielding of activation indicators under reactor irradiation. Research methods: modeling and implementation of neutronic calculations of reaction rate of activation using MCNP5 program depending on indicators thickness and nuclear concentration of isotopes; selection of analytical dependencies for calculation of self-shielding factors. Results. The paper introduces the results of neutronic calculations of self-shielding factors for activation gold/tantalum indicators, used as an indicator of activation by neutron irradiation. The authors obtained the dependences of correction factors on indicator thickness, the analytical formulas for the indicator and dependences of the reaction rate on the concentration of isotopes. The results of calculations will be used while conducting the Instrumental Neutron Activation Analysis for nuclear engineering structural materials by single-limit comparative method of k0-standartization at IVG.1M research reactor.
