Intercomparison study of atmospheric 222Rn and 222Rn progeny monitors

International audienceThe use of the noble gas radon (222 Rn) as a tracer for different research studies, for example observation-based estimation of greenhouse gas (GHG) fluxes, has led to the need of high-quality 222 Rn activity concentration observations with high spatial and temporal resolution. So far a robust metrology chain for these measurements is not yet available. A portable direct atmospheric radon monitor (ARMON), based on electrostatic collection of 218 Po, is now running at Spanish stations. This monitor has not yet been compared with other 222 Rn and 222 Rn progeny monitors commonly used at atmospheric stations. A 3-month intercomparison campaign of atmospheric 222 Rn and 222 Rn progeny monitors based on different measurement techniques was realized during the fall and winter of 2016-2017 to evaluate (i) calibration and correction factors between monitors necessary to harmonize the atmospheric radon observations and (ii) the dependence of each monitor's response in relation to the sampling height and meteorological and atmospheric aerosol conditions. Results of this study have shown the following. (i) All monitors were able to reproduce the atmospheric radon variability on a daily basis. (ii) Linear regression fits between the monitors exhibited slopes, representing the correction factors, between 0.62 and 1.17 and offsets ranging between −0.85 and −0.23 Bq m −3 when sampling 2 m above ground level (a.g.l.). Corresponding results at 100 m a.g.l. exhibited slopes of 0.94 and 1.03 with offsets of −0.13 and 0.01 Bq m −3 , respectively. (iii) No influence of atmospheric temperature and relative humidity on monitor responses was observed for unsaturated conditions at 100 m a.g.l., whereas slight influences (order of 10 −2) of ambient temperature were observed at 2 m a.g.l. (iv) Changes in the ratio between 222 Rn progeny and 222 Rn monitor responses were observed under very low atmospheric aerosol concentrations. Results also show that the new ARMON could be useful at atmospheric radon monitoring stations with space restrictions or as a mobile reference instrument to calibrate in situ 222 Rn progeny monitors and fixed radon monitors. In the near future a long-term comparison study between ARMON, Published by Copernicus Publications on behalf of the European Geosciences Union. 2242 C. Grossi et al.: Intercomparison of 222 Rn and 222 Rn progeny monitors HRM, and ANSTO monitors would be useful to better evaluate (i) the uncertainties of radon measurements in the range of a few hundred millibecquerels per cubic meter to a few becquerels per cubic meter and (ii) the response time correction of the ANSTO monitor for representing fast changes in the ambient radon concentrations

Characterization of a novel large area microdosimeter system for low dose rate radiation environments

ｖA feasibility study is presented on a newly developed microdosimetry system named Octobox, for its application in low dose rate, mixed radiation environments. A full characterization of the device was performed at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan, out-of-field of various heavy ion radiation fields — 290 MeV/u 12C, 230 MeV/u and 490 MeV/u 28Si and 400 MeV/u 20Ne ions, as well as a low dose rate 222Rn environment at the Australian Nuclear Sciences and Technology Organization (ANSTO). The device was shown to collect adequate statistics in a short period of time when compared to the MicroPlus probe with a single microdosimeter, while accurately measuring microdosimetric quantities and the corresponding average quality factor () and dose equivalent (H) of the mixed radiation field. Good agreement of the microdosimetric spectra was also shown with Geant4 simulations for all presented ion fields. Based on the findings in this study, the Octobox is capable of being applied in mixed, low dose rate, radiation environments such as those encountered in space and aviation, as well as in underground mines for radiation protection purposes