Sources contributing to radionuclides in the environment: With focus on radioactive particles

Abstract

To assess environmental impact and risks associated with radioactive contamination of ecosystems, links must be established between the source term and deposition, ecosystem transfer, biological uptake and effects in exposed organisms. In transport, dose, impact and risk models, information on the source term and the deposition densities is therefore an essential input. Following severe nuclear events, a major fraction of refractory radionuclides can be present as radioactive particles. The particle characteristics will depend on the source and the release scenarios, and such information should be included in the source term. Furthermore, assessments are traditionally based on average bulk mass or surface activity concentrations of radionuclides in environmental compartments (Bq/kg, Bq/m2 or Bq/L), assuming that a limited number of samples are representative. Localised heterogeneities such as particles will, however, be unevenly distributed, and representative sampling can be questionable. Due to structural properties, dissolution of radionuclides from particles prior to measurements may be partial. For areas affected by particle contamination, the inventories can be underestimated, and impact and risk assessments may suffer from unacceptable large uncertainties if radioactive particles are ignored. The present chapter will focus on key sources contributing to radioactivity in the environment, especially radioactive particles, and will summarise the most important particle characterisation techniques available.