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Hot particles — a challenge within radioecology
Journal of Environmental Radioactivity 53 (2001) 267–268
Millennial Editorial Series
Hot particles } a challenge within radioecology Brit Salbu Laboratory of Analytical Chemistry, Department of Chemistry and Biotechnology, Agricultural University of Norway, N-1432 Aas, Norway
A major fraction of the radionuclides released during historical nuclear events has been associated with particles. Radioactive or hot particles are identified within nuclear weapon test sites (Nevada, US; Maralinga, Australia; Mururoa, French Polynesia; Semipalatinsk, Kasahkstan etc.), in fallout from nuclear reactor explosions (Chernobyl, Ukraine) or fires (Windscale, UK), and in areas contaminated by crashes of reactor-powered satellites (Cosmos 954 in Canada) or of aircraft carrying nuclear weapons (Thule, Greenland; Palomares, Spain). Particles are also released in authorised discharges from reprocessing plants (Sellafield, UK; Mayak, Russia) and from radioactive wastes dumped for instance in the Kara Sea. Therefore, releases of radioactive particles have occurred more frequently than perhaps usually anticipated. Today, there are a number of potential sources which may contribute to significant radioactive contamination in the future; from accidents associated with the nuclearfuel cycle and from nuclear-weapons-related activities. According to the IAEA, 436 civil nuclear reactors are in operation, although ageing is an increasing problem, and another 38 are under construction. Although considered safe, the Three Mile Island accident demonstrated that ‘‘improbable’’ accidents may happen, while the Chernobyl accident demonstrated that the impact of a nuclear explosion could be far more serious than previously assumed, contaminating areas up to 2000 km from the site. And countermeasures are still needed in these areas. Furthermore, the inventory of waste is steadily increasing, and about 1000 t of plutonium from power reactors, 100 t Pu from civil reprocessing, 100 t Pu from dismantling warheads had to be stored in 1998. Accidents associated with unsafe handling and storage not only of nuclear wastes but also of nuclear weapons cannot be excluded. Finally, the frequency of unforeseen situations or threats arising from smuggling of nuclear material, sabotage and radiological or nuclear terrorism has increased internationally. From a preparedness point of view, high competence within radioecology and impact assessments should therefore be increasingly important internationally. E-mail address: [email protected] (B. Salbu). 0265-931X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 5 - 9 3 1 X ( 0 0 ) 0 0 1 2 0 - X
268
B. Salbu / J. Environ. Radioactivity 53 (2001) 267–268
In all serious events with significant releases of refractory elements, hot particles should be expected. Unless the source term is well characterised, model predictions of the dispersion, ecosystem transport and dose assessment will suffer from unacceptably large uncertainties. Hot particles represent point sources of radiological significance; particles may contribute to localised skin doses or particles inhaled or ingested can be retained within animals and humans for an unexpectedly long time. To assess the impact of hot particle contamination of ecosystems and to implement cost-efficient measures, information is needed on particle characteristics and on the behaviour of particles and associated radionuclides in the ecosystem. After deposition, weathering of particles occurs and associated radionuclides are subsequently released. Until weathering is significant, however, the ecosystem transfer of particle-associated radionuclides will be delayed, and the delay is sourcedependent and release-related. Thus, ecosystem transfer of mobile radionuclides (e.g. 90 Sr) may occur decades after deposition of the (e.g. 90Sr bearing) particles. Kinetic information on processes influencing particle weathering, mobility and bioavailability of released radionuclide species is essential to impact assessments, probably even more vital for prognosis than the apparent radionuclide distributions in the ecosystem compartments. To improve knowledge on the behaviour of hot particles in the ecosystem, military nuclear weapon test sites representing different sources and different ecosystems should be opened for such investigations. Characterisation of source terms including hot particles in the submicron to fragments range represents an analytical challenge. By introducing advanced technologies (synchrotrons, lasers, time-of-flight systems, etc.) to radioecology, however, major advances within this field can be achieved. Such efforts may also vitalise the field of radioecology. As the need for recruitment may be the most serious threat to the development of radioecology in the future, it is essential that scientific issues are highly relevant and that technological challenges are seen as an attractive choice for future students.
Millennial Editorial Series
Hot particles } a challenge within radioecology Brit Salbu Laboratory of Analytical Chemistry, Department of Chemistry and Biotechnology, Agricultural University of Norway, N-1432 Aas, Norway
A major fraction of the radionuclides released during historical nuclear events has been associated with particles. Radioactive or hot particles are identified within nuclear weapon test sites (Nevada, US; Maralinga, Australia; Mururoa, French Polynesia; Semipalatinsk, Kasahkstan etc.), in fallout from nuclear reactor explosions (Chernobyl, Ukraine) or fires (Windscale, UK), and in areas contaminated by crashes of reactor-powered satellites (Cosmos 954 in Canada) or of aircraft carrying nuclear weapons (Thule, Greenland; Palomares, Spain). Particles are also released in authorised discharges from reprocessing plants (Sellafield, UK; Mayak, Russia) and from radioactive wastes dumped for instance in the Kara Sea. Therefore, releases of radioactive particles have occurred more frequently than perhaps usually anticipated. Today, there are a number of potential sources which may contribute to significant radioactive contamination in the future; from accidents associated with the nuclearfuel cycle and from nuclear-weapons-related activities. According to the IAEA, 436 civil nuclear reactors are in operation, although ageing is an increasing problem, and another 38 are under construction. Although considered safe, the Three Mile Island accident demonstrated that ‘‘improbable’’ accidents may happen, while the Chernobyl accident demonstrated that the impact of a nuclear explosion could be far more serious than previously assumed, contaminating areas up to 2000 km from the site. And countermeasures are still needed in these areas. Furthermore, the inventory of waste is steadily increasing, and about 1000 t of plutonium from power reactors, 100 t Pu from civil reprocessing, 100 t Pu from dismantling warheads had to be stored in 1998. Accidents associated with unsafe handling and storage not only of nuclear wastes but also of nuclear weapons cannot be excluded. Finally, the frequency of unforeseen situations or threats arising from smuggling of nuclear material, sabotage and radiological or nuclear terrorism has increased internationally. From a preparedness point of view, high competence within radioecology and impact assessments should therefore be increasingly important internationally. E-mail address: [email protected] (B. Salbu). 0265-931X/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 2 6 5 - 9 3 1 X ( 0 0 ) 0 0 1 2 0 - X
268
B. Salbu / J. Environ. Radioactivity 53 (2001) 267–268
In all serious events with significant releases of refractory elements, hot particles should be expected. Unless the source term is well characterised, model predictions of the dispersion, ecosystem transport and dose assessment will suffer from unacceptably large uncertainties. Hot particles represent point sources of radiological significance; particles may contribute to localised skin doses or particles inhaled or ingested can be retained within animals and humans for an unexpectedly long time. To assess the impact of hot particle contamination of ecosystems and to implement cost-efficient measures, information is needed on particle characteristics and on the behaviour of particles and associated radionuclides in the ecosystem. After deposition, weathering of particles occurs and associated radionuclides are subsequently released. Until weathering is significant, however, the ecosystem transfer of particle-associated radionuclides will be delayed, and the delay is sourcedependent and release-related. Thus, ecosystem transfer of mobile radionuclides (e.g. 90 Sr) may occur decades after deposition of the (e.g. 90Sr bearing) particles. Kinetic information on processes influencing particle weathering, mobility and bioavailability of released radionuclide species is essential to impact assessments, probably even more vital for prognosis than the apparent radionuclide distributions in the ecosystem compartments. To improve knowledge on the behaviour of hot particles in the ecosystem, military nuclear weapon test sites representing different sources and different ecosystems should be opened for such investigations. Characterisation of source terms including hot particles in the submicron to fragments range represents an analytical challenge. By introducing advanced technologies (synchrotrons, lasers, time-of-flight systems, etc.) to radioecology, however, major advances within this field can be achieved. Such efforts may also vitalise the field of radioecology. As the need for recruitment may be the most serious threat to the development of radioecology in the future, it is essential that scientific issues are highly relevant and that technological challenges are seen as an attractive choice for future students.