Quantification and computational modelling of radiation doses while handling Neutron Activation Analysis samples
The vast majority of radiation protection guidelines in nuclear facilities usually relate to a few radiation sources in very controlled environments. There are 111 research reactors where neutron activation analysis (NAA) is a significant research and teaching component. Although many reports and research articles detail the safety procedures at power reactors and government-run research facilities, few reports have been published specifically for NAA laboratories. This leads to little or no formal protocols to minimize exposure. In particular, NAA can yield various exposures due to different types of samples and neutron fluxes. Unlike any other type of radiation laboratory, an NAA lab can contain a large variety of radioactive isotopes resulting from activation products with varying degrees of half-lives and different strengths of gamma-rays and beta particles. Typically, it is challenging to predict exposure rates for each irradiation run. Dose rates were computed using MCNP 6.2, a Monte Carlo code developed by Los Alamos National Laboratory (LANL) for radiation transport. The MCNP 6.2 model is used to computationally irradiate sample materials in several positions in the TRIGA reactor core using various NIST standard reference materials and typical NAA samples. In a second MCNP 6.2 model, two different computational phantoms are modeled: 1) whole-body phantom and 2) hand phantom. These phantoms helped develop approximate absorbed doses that a researcher could encounter while handling NAA samples.