Electron paramagnetic resonance for dosimetry in freshwater aquatic environments

Abstract

This thesis explores the feasibility of detection of radiological contamination in aquatic environments through Electron Paramagnetic Resonance (EPR) spectroscopy. Exposure of freshwater ecosystems is possible as a result of accidents involving facilities of the nuclear fuel cycle. Since this can result in contamination with nuclides such as 90Sr, methods for determining radiation doses in the environment were explored. Specifically for shelled species, the concentration factor for 90Sr was found to have the largest influence on the correct prediction of radiation dose due to this nuclide. Possible doses to zebra mussels due to historic accidents were calculated in excess of 2 Gy in some instances. EPR is a method that is used to detect unpaired electrons that are induced by absorption of ionizing radiation in calcified tissues and as such, it measures lifetime dose to shells. From three organisms investigated, only Dreissenid mussels showed a radiation induced signal under the dose of 20 Gy. A linear relationship of the peak-to-peak height of the line at g = 2:0034 was established and used to improve the quantification of absorbed dose. Shells from different sampling dates were discovered to have different background EPR signals. For the sample group with the lowest background, it was possible to resolve doses as low as 0:2 Gy, thus reducing the value of 2 Gy, previously reported in literature. This provides further validation that EPR dosimetry of shelled species has the potential to contribute to better characterization of absorbed doses in aquatic environments.