During the years, radioactive particles containing refractory radionuclides such as uranium and plutonium have been released from the nuclear weapon and reactor cycles. The particle characteristics such as radionuclide/metal composition as well as isotope/atom ratios will reflect the source, while particle size distributions, crystallographic structures and oxidation states depend on the release scenarios. Radioactive particles, ranging from submicrons to fragments, are heterogeneously distributed in the environment, and representative sampling can be difficult to attain, dissolution of particle samples prior to measurements can be incomplete, and subsequently inventories at contaminated sites can be underestimated. When radioactive particles enter the environment, weathering processes occur and subsequently associated radionuclides are mobilized. Particle contaminated soils or sediments can therefore act as diffuse sources of radionuclides in the future.
Radioactive particles can carry substantial amounts of activity, and act as point sources, providing doses to man and the environment. The mobility, biological uptake and effect of particle-bound radionuclides, deviating from present knowledge on simple ions, have, however, largely been ignored in radiation dosimetry, impact and risk estimates. If ignored, the overall uncertainties in dose, impact and risk assessment related to particle contaminated areas can be unacceptable high. As particle releases also should be expected in the future, the analytical programme should include advance techniques providing information on particle characteristics influencing weathering, mobility and biological uptake. The present paper will present a summary on sources associated with radioactive particle releases to the environment, and focus on particle characteristics of relevance for impact and risk assessment.