Sodium-22 (22Na, half-life 2.603 years) is a cosmogenic radionuclide mainly produced in the stratosphere by nuclear spallation reactions of cosmic rays on 40Ar. Due to the very low concentration levels normally reached in the environment, 22Na poses no significant radioprotection threats: actually, the effective doses delivered to humans can hardly exceed a few nSv per year, a very negligible value. However, the measurements of this radionuclides can be very interesting for atmospheric circulation and climatic studies. Unfortunately, the difficulty of 22Na detection, due to its very low concentration levels, has prevented the gathering of large and widespread time series of this radionuclide. In this paper, a method for the retrospective measurements of 22Na in the atmosphere, starting from the gamma spectra (hyperpure germanium detectors (HPGe) detectors) of wet and dry deposition samples stored in our databases is proposed and validated. The method was applied to spectra samples gathered in the context of the Italian National Radioactivity Monitoring Network (RESORAD) and allowed the detection of the very low atmospheric activity concentration values of 22Na present at ground level. The results obtained with the new method are discussed and compared for validation with the available experimental values. Finally, some possible applications to environmental studies are also highlighted and suggested.
During emergencies following a major nuclear accident a prompt and accurate characterisation of the radioactive cloud is one of the main task of any radioactivity monitoring system. This task is usually performed by means of γ-spectrometry High Purity Germanium (HPGe) measurements on atmospheric particulate samples gathered by means of high-volume pumps. The key parameters describing the performances of a monitoring system are the Minimum Detectable Activities (MDAs) of the most relevant radionuclides. These parameters depend on a number of factors related to the efficiency of the available germanium detector, the volume of air filtered by the sampling devices and the γ-decay scheme of each radionuclides as well. Besides the MDAs, another very important characteristic of a monitoring system, especially during an evolving emergency, is its capability of giving reliable results at a given and constant pace. It is therefore important to define the time resolution of the monitoring system, i.e. the minimum time needed to produce the data, namely the activity concentrations of the radionuclides in the atmosphere. The optimization of the measurements procedures are discussed in this work: in particular it is demonstrated that, being t the time resolution of the monitoring system, the lowest MDAs can be achieved with a sampling time given by (2/3)·t and a counting time of (1/3)·t. Finally, the MDAs achievable for a standard monitoring system based on a 30% HPGe detector are calculated for all the most important fission products.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.