Electron paramagnetic resonance spectroscopy for the detection of radiation exposure in dreissenid mussels.

Electron paramagnetic resonance (EPR) spectroscopy, established for radiation measurements in calcified tissues, was identified as a methodology that merits investigation for the purpose of environmental radiation measurements using dreissenid mussels from the Great Lakes. With the refinement of sample preparation and measurement protocols, a linear relationship of dose with the peak-to-peak height of the radiation-induced signal at g = 2.0034 was established. A dedicated analysis algorithm was developed to process batches of samples, eliminating the need for manual peak-to-peak height measurement. Varying background EPR signals were identified in different sampling groups, with samples gathered in winter having a markedly lower background signal. Through optimisation of spectrum acquisition normalisation methods, it was possible to resolve doses as low as 0.2 Gy. This work provides further validation that EPR dosimetry of shelled species has the potential to contribute to better characterisation of absorbed doses in aquatic environments.

A Practical Method for EPR Dosimetry Using Alanine Powder.

ABSTRACT: This work investigates alanine powder, an inexpensive and versatile material compared to alanine pellets, as a standardized dosimeter for the alanine-EPR system using a Bruker EMX-Micro spectrometer. The feasibility of this method was investigated, and a calibration curve was produced using 40 dosimeters, which were prepared by tightly packing DL-alanine powder in polypropylene microcentrifuge tubes. The dosimeters were irradiated to doses ranging from 0.2-20 Gy using a 60 Co source. A dosimeter handling and measurement protocol was established for all dosimeters. The dosimetric signal was evaluated by measuring the peak-to-peak height of the central resonance peak, and the dose response of alanine powder dosimeters showed a linear behavior in the investigated dose range with relative errors below 13%. Measurement repeatability and reproducibility were tested to show the errors associated with sample placement in the cavity and with the overall measurement method, with both tests showing relative errors below 7%. As an inexpensive material compared to pellet dosimeters, alanine powder has a strong potential to be used as a standardized material for radiation dosimetry applications. The scope of this work is to present an effective and comprehensive methodology with accompanying analysis scripts for dosimetry with alanine powder that is useful in a wide range of applications and dose requirements.

On the Use of Location and Occupancy Factors for Estimating External Exposure From Deposited Radionuclides.

Providing a dose estimate for the exposed population is crucial in the case of deposition of a known radioactive material, either through an accident or during routine operations. In the absence of detailed information on each individual, knowing the demographics of the affected population concerning occupational habits and housing allows the determination and use of appropriate location and occupancy factors required for exposure and dose calculations. The previous approach in the United Nations Scientific Committee on the Effects of Atomic Radiation 2013 report, published in 2014, used time-dependent location factors and occupancy factors based on age and occupation. The newly published methodology in the United Nations Scientific Committee on the Effects of Atomic Radiation 2016 report (2017) is simplified, using a single time-independent location factor for indoor occupancy, as well as a single occupancy factor that is independent of the age and occupation of the population considered. In this work the two approaches are compared for different population groups and housing types in the case of both a short-lived and a long-lived radionuclide. It was found that the new simplified methodology, while overestimating the integrated effective dose over 100 y for Cs and Cs, also underestimates the dose on short timescales, especially for the shorter-lived Cs. Additionally, the dose rate is significantly underestimated for certain types of buildings with higher location factors. This was found for both radionuclides in the first year of exposure. In the case of short-lived Cs, the integrated effective dose after 100 y is also underestimated in certain cases. It can be concluded that, while the simplified methodology can reasonably and successfully be applied in cases where dose due to deposition (1) is not the dominant pathway and (2) is part of multistep calculations, caution must be exercised in more complex exposure situations, especially when performing dose assessment in response to an accident.