Neutron/Gamma Mixed Spectrum Radiolysis-based Aqueous Dosimetry

Abstract

This work develops a method to use an aqueous dosimeter in a mixed radiation field to determine separate measurements of neutron and gamma dose. Based on radiolysis of both Fricke and Methyl Viologen (MV) solutions, activation analysis and reactor simulation are combined to determine neutron dose and neutron radiolysis. This is subtracted from the total measured radiolysis to infer a gamma dose. The Fricke dosimeter was able to give repeatable results for the neutron and gamma doses over a number of days for a variety of shielding configurations. Impurities in the MV dosimeter prevented it from providing repeatable results, but qualitative comparison to the Fricke dosimeter indicated that it could be a viable approach. The method found that the reactor simulation, using MCNP5, can be used for accurate neutron simulations but does not account for all the source terms for gamma dose simulation. A neutron G-value for the Fricke dosimeter was developed by combining proton radiolysis simulations with results from MCNP5 and NJOY.