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Completed CRP: Environmental Behaviour and Potential Biological Impact of Radioactive Particles (K41013)

Success story

David Child from Australian Nuclear Science and Technology Organisation (ANSTO) taking samples in November 2015 at the Mosaic II test site, Montebello Islands, Australia, where there were numerous glassy particles. The inset displays color-coded images of particles indicating their elemental compositions of Fe (red), Pb (green) and U (blue) as revealed by X ray florescence spectrometry. (Photo: ANSTO)

Results of a recently completed IAEA coordinated research project (CRP) help the global science community better understand and predict the long term environmental behaviour and potential biological impact of radioactive particles.

The existing system for assessing the impact of environmental radiation on people, animals and plants is essentially based on assumptions of continuous and uniform radioactive sources. Contrary to these assumptions, real life often demonstrates greater diversity of existing forms of radioactive contaminants, which range from continuous substances, like gases and fluids, to highly heterogeneous solid refractory particles.

Radioactive contamination originated from the past and current activities and events, such as nuclear weapon tests, industrial and military practices, radiation incidents and accidents, mining and natural resource exploration result in increased amounts of radioactive materials. A significant part of those exists in form of particles. The variety of existing particulate forms, their environmental and biological behaviour, mobility and bioavailability, as well as of associated radiological threats all justify goals for a systematic and thorough study.

Radioactive particles are now understood to be more prevalent in the environment than previously assumed, thus leading to new research tasks in measurement science and analytical techniques, radiobiology, dosimetry, remediation and recovery, radioecology and health risks assessment.

The recently concluded CRP addressed the following specific objectives:

  • Long term environmental behaviour of radioactive particles, focusing on their solubility in soil, mobility in the environment and food webs, bioavailability.
  • Classification of radioactive particles for the purposes of radiation protection and remediation planning.
  • Relationships and links between nuclear sources, characteristics of radioactive particles and radioecological parameters of radionuclide transfer.
  • Challenges in human and environmental dosimetry arising from exposures to radioactive particles and non-continuous radiation sources.
  • Relevant endpoints and methods for assessing biological effects for environmental organisms exposed to radioactive particles.
  • Understanding specific radiobiological hazards for human and biota arising from exposures to radioactive particles.
  • Promoting collaboration among world analytical laboratories studying environmental impact of radioactive particles.

The CRP activities led to improved scientific knowledge on properties and environmental behaviour of particulate radioactive materials and their abundance, forms, properties, and associated hazards.

The project provided a cooperation framework for 18 research organisations from 14 countries across four continents – Australia, Europe, North America and Asia. Among the CRP activities and outputs were:

  • A special issue of the Journal of Environmental Radioactivity, entitled “IAEA: coordinated research on radioactive particles”, containing 11 papers and an editorial.
  • 35 scientific papers in peer-reviewed literature. 15 other contributions, such as conference presentations and abstracts. A submitted manuscript.
  • 11 PhD degrees completed (with another 3 ongoing) in 7 countries (Germany, Norway, Russia, Spain, Sweden, Ukraine, United Kingdom).
  • Outreach: the CRP was presented at the 5th International Symposium on the System of Radiological Protection, held in November 2019 by the International Commission on Radiological Protection (ICRP).

Outcomes of the CRP

The work performed within the CRP demonstrated that the particle composition is determined by properties of a radioactive or radiation source, while the particle characteristics of relevance for ecosystem transfer and biological uptake are largely defined by release and deposition scenarios.

Particle weathering rates and the subsequent remobilization and ecosystem transfer of particle-associated radionuclides depend on the particle characteristics (e.g., composition, structure, oxidation state). Soil and sediment serve as sinks for particles, which can then act as diffuse sources of radioactivity if particles’ weathering occurs over time. Correspondingly, information on particle weathering rates and potential biological uptake and effects appear as essential for assessing long term radiological impact and consequences.

The objective information on properties of radioactive particles released to the environment due to past practices or events and on associated radiological threats is needed. In areas affected by particle contamination, a substantial amount of radioactivity can be present in particulate form, so the radioactive contamination can be unevenly distributed, and the inventories can be underestimated. Correspondingly, estimates of radiological impacts to human health and to the environment may become biased with unacceptably large uncertainties if the radioactive particles are ignored and continuity assumptions are utilised.

Click for further information on this CRP.

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