Modeling capture rate changes as a function of hydrogen content in epithermal neutron activation analysis samples using an absorbent polymer

McLaughlin, Kevin Ross
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Neutron activation analysis measurements are known to be affected by the presence of hydrogen within the sample in question. However, the mechanism of this phenomenon, particularly in epithermal neutron activation analysis, has not been fully studied and quantified. Using MCNP6 models of the University of Texas at Austin epithermal pneumatic tube irradiation location within the Nuclear Engineering Teaching Laboratory’s TRIGA reactor, the effects of the presence of hydrogen in samples are measured. Mixtures of water and sodium acrylate, a polymer with strong water absorption and retention properties, are modeled in varying ratios and densities, creating a distribution of sample materials with varying hydrogen contents. These models provide insight into the neutron capture rate changes that take place within hydrogenous epithermal neutron activation analysis samples. The results show a quadratic relationship between capture rates and hydrogen mass within the samples.