Schematic representation of radon levels increasing in the air. Against a blue sky with white clouds a red arrow climbs upwards over the words RADON in large letters
Case Study Overview

Using the radon tracer method to help improve greenhouse gas inventories

Radon (Rn-222) is a colourless, odourless, radioactive gas released from many rocks and soils in the Earth’s surface. Whilst being the largest source of public exposure to naturally occurring radioactivity – causing between 3% to 14% of all lung cancers – it can also have a role to play in understanding the movements of greenhouse gases which are driving climate change.

Challenge

Radon (Rn-222) is a radioactive gas released from soil and building materials and is the largest source of public exposure to naturally occurring radiation. Monitoring its levels is important in this regard but can also act as an additional tool for assessing the emissions of Greenhouse Gases (GHGs) such as carbon dioxide (CO2) and methane (CH4), that are contributing to climate change.

Radon is released almost uniformly from all land masses and its half-life of 3.8 days is sufficient for it to diffuse both vertically and horizontally in the atmosphere. Linking GHG measurements to Rn-222 via a method called the Radon Tracer Method (RTM) can inform on where and how GHGs are distributed - enabling better estimations of greenhouse gas emission inventories, consensus building, and targeted actions on reductions. This approach is currently of interest for the Integrated Carbon Observation System Research Infrastructure (ICOS), who produce standardised, high-precision and long-term observations on GHGs.

Several factors have limited the RTM application, however. Atmospheric Rn-222 can occur at very low activity concentrations depending upon altitude so detectors must be extremely sensitive – down to 1 Bq per m3. Radon breakdown products, such as the metal polonium 210 (Po-210), can also precipitate in detectors, contaminating instruments and affecting measurement accuracy. Improvements in radon monitoring were required to take full advantage of the RTM approach.

Solution

During traceRadon, a prototype of the Atmospheric Radon MONitor (ARMON) of the Institute of Energy Technologies of the Universitat Politècnica de Catalunya (INTE-UPC) was improved, built and finally fully characterised at PTB, the National Metrology Institute of Germany.

The ARMON electrostatically collects the Rn-222 decay product Polonium (Po-218) on the surface of a Passivated Implanted Planar Silicon (PIPS) detector. Measuring the alpha particles produced during polonium decay provides data of the respective Rn-222 level.

Experiments at INTE-UPC improved the detection volume, acquisition and drying modules, and a user interface was added to remotely control different modules and provide results in real time. The ARMON (v2) was compared with radon monitors at Atmospheric Monitoring Stations in Spain, France, and Germany and assessed for variables influencing readings such as moisture, temperature and pressure. Traceability to the SI was established by PTB using new low-radon-emanation sources and an advanced calibration instrument developed during the project.

Results indicated a sensitivity of the new instrument of around 21 counts per hour per Bq/m3, leading to a decision threshold of only 0.05 Bq/m3 with a detection volume of just 20 L. The low space requirement can be an advantage when it comes to installation at atmospheric stations.

Impact

The ARMON, improved within traceRadon, has now been commercialised by Radonova – a global leader in radon measurement processes and procedures, conducting large-scale radon measurement in over 80 countries.

The ARMON is portable, automatic and, unlike other radon instruments, can clearly distinguish between Rn-222 and the radon isotope Thoron (Rn-220) as well as decay products such as Po-214 and contaminating Po-210. This means it does not require periodic calibration to account for this isotope, which usually causes background noise in other radon monitors. Using Po-218 to detect radon also allows it to significantly reduce the response time of the instrument without applying any data post-processing. A fast time response is essential for monitoring stations to accurately map rapid changes in radon level.

Radonova, whose radon experts were involved in the design of several well-known detectors such as the ATMOS, MARKUS, SPIRIT and Robin, believe that the ARMON can make a significant improvement to atmospheric radon monitoring in Europe and the application of the Radon Tracer Method.

This will not only help improve GHG inventories and provide more focused mitigation responses, but also help identify areas with high radon activity concentrations, providing greater public safety to this ubiquitous gas.

Image showing concept of radon danger

Providing new traceability chains from the laboratory to the field for radon (Rn-222) monitoring

The traceRadon project developed:

 

- first traceable measurements for low-level outdoor radon activity concentrations (1 Bq/m3 to 100 Bq/m3).

- two new low-level Rn-222 emanation sources (< 100 Bq/m3) for traceable calibration of atmospheric radon monitors and a radon “exhalation bed” that can be used as a calibration facility.

- a new instrument, the Integrated Radon Source Detector, for low activity radon concentrations, provided traceability to two new transfer standards, the ANSTO 200 L and ARMON v2.0 – providing SI field traceability for the first time.

- the first validated procedure for the Radon Tracer Method (RTM) for use at Atmospheric Monitoring Stations.

- validated radon flux measurements and flux maps for the identification of Radon Priority Areas (RPA).

- a new service on the Integrated Carbon Observation System carbon portal for radon flux maps.

 

The instrumentation and methodology for low radon levels in the environment will help determine GHG emission reduction strategies and improve public protection from radiation.

Contact

  • Category
  • EMPIR,
  • Environment,
  • EMN Radiation Protection,
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