Browsing by Author "Röttger, S"

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    Field testing of a portable two-filter dual-flow-loop 222Rn detector
    (Copernicus GmbH, 2021-04-19) Chambers, SD; Morosh, V; Griffiths, AD; Williams, AG; Röttger, S; Röttger, A
    An overlapping need exists between the climate science, air quality and radiological protection communities for a robust, portable and direct monitor of atmospheric 222Rn concentrations typical of the ambient outdoor atmosphere. To reliably characterise afternoon radon concentrations, or resolve daytime vertical radon gradients in the atmospheric boundary layer (requirements for radon measurements to be used to evaluate the performance of chemical transport models), detection limits of ≤0.2 Bq m-3 at an hourly temporal resolution are required. Commercial portable radon detectors are mainly designed for indoor use, and the best of these has a detection limit of ≥2 Bq m-3 for hourly sampling, with an approximate uncertainty of 60% at typical outdoor daytime radon concentrations. Here we introduce a portable (200 L) version of the two-filter dual-flow-loop radon detector, designed and built by ANSTO in collaboration with the EMPIR 19ENV01 traceRadon project. While not as compact as commercial monitors (standing 1.6 m tall, and 0.48 m wide), its longest component is 1.2 m, enabling transportation in a standard utility vehicle or 4x4 (and can fit inside a 19” instrument rack). Constructed of marine grade stainless steel, it is weather resistant, robust, and suitable for long-term, continuous, autonomous deployment; in fact it is fully remotely controllable if a networked computer is available. The estimated lower limit of detection is 0.17 Bq m-3 for hourly observations, and the counting uncertainty at typical ambient outdoor radon concentrations is around 7%. Additional uncertainty associated with current calibration techniques, which inject calibration gas on top of ambient sampled air, varies from 2-6%. Some objectives of the traceRadon project include establishing direct calibration traceability to the SI and developing an improved closed-loop calibration technique, using a new, low activity Radium-226 source. If successful, the absolute accuracy of the 200 L radon detector at typical ambient outdoor concentrations could be kept well below 15% for hourly observations. This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. 19ENV01 traceRadon denotes the EMPIR project reference.
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    Portable high sensitivity Rn-222 detector with an Si traceable calibration
    (South Pacific Environmental Radioactivity Association, 2022-11-29) Chambers, SD; Röttger, S; Griffiths, AD
    Among the key limitations of “top-down” techniques such as the Radon Tracer Method to characterise local- to regional-scale emissions of greenhouse gases is reliable representation of the spatial and temporal variability in radon concentrations and fluxes (Röttger et al. 2021; Levin et al. 2021). Furthermore, the utility of complementary outdoor radon monitoring for the identification and characterisation of radon priority areas is also becoming more widely recognised. As such, the availability of reliable and accurate monitors of outdoor radon concentration (1≤ARn<100 Bq.m-3) is of significant interest to both the climate and radiation protection research communities. Until recently, however, calibrations traceable to the International System of Units (SI) were only available for concentrations ≥100 Bq.m-3. Among the key objectives of the EMPIR 19ENV01 traceRadon Project§ are the development low-activity radon sources to enable SI traceable calibrations between (1 – 100) Bq.m-3 and portable radon monitors capable of reliably measuring radon concentrations in this range and transferring an SI traceable calibration to other radon monitors. Here we present the fruits of a collaboration between ANSTO and Physikalisch-Technische Bundesanstalt (PTB) as part of traceRadon, namely, a portable two-filter dual-flow-loop radon detector with a detection limit of <0.2 Bq.m-3 and 30-minute temporal resolution. In conjunction with novel calibration sources developed by PTB, the compact size and low sampling flow rate of this monitor enable SI traceable calibration under laboratory and field conditions. The new detector (Chambers et al. 2022), sources (Mertes et al. 2022) and calibration method (Röttger et al. 2021) are introduced, measurement characteristics investigated, and an example provided of a calibration transfer from the portable monitor to a separate monitor operating under field conditions. The portability, reliability and sensitivity of this portable detector will facilitate the harmonization of radon monitoring being conducted in radiation protection and climate research station networks globally.