Retention Of Radioactive Particles Research Articles

Challenges associated with the behaviour of radioactive particles in the environment

A series of different nuclear sources associated with the nuclear weapon and fuel cycles have contributed to the release of radioactive particles to the environment. Following nuclear weapon tests, safety tests, conventional destruction of weapons, reactor explosions and fires, a major fraction of released refractory radionuclides such as uranium (U) and plutonium (Pu) were present as entities ranging from sub microns to fragments. Furthermore, radioactive particles and colloids have been released from reprocessing facilities and civil reactors, from radioactive waste dumped at sea, and from NORM sites. Thus, whenever refractory radionuclides are released to the environment following nuclear events, radioactive particles should be expected.Results from many years of research have shown that particle characteristics such as elemental composition depend on the source, while characteristics such as particle size distribution, structure, and oxidation state influencing ecosystem transfer depend also on the release scenarios. When radioactive particles are deposited in the environment, weathering processes occur and associated radionuclides are subsequently mobilized, changing the apparent Kd. Thus, particles retained in soils or sediments are unevenly distributed, and dissolution of radionuclides from particles may be partial. For areas affected by particle contamination, the inventories can therefore be underestimated, and impact and risk assessments may suffer from unacceptable large uncertainties if radioactive particles are ignored. To integrate radioactive particles into environmental impact assessments, key challenges include the linking of particle characteristics to specific sources, to ecosystem transfer, and to uptake and retention in biological systems. To elucidate these issues, the EC-funded COMET and RATE projects and the IAEA Coordinated Research Program on particles have revisited selected contaminated sites and archive samples. This COMET position paper summarizes new knowledge on key sources that have contributed to particle releases, including particle characteristics based on advanced techniques, with emphasis on particle weathering processes as well as on heterogeneities in biological samples to evaluate potential uptake and retention of radioactive particles.

Retention of radioactive particles and associated effects in the filter-feeding marine mollusc Mytilus edulis

Radioactive particles are aggregates of radioactive atoms that may contain significant activity concentrations. They have been released into the environment from nuclear weapons tests, and from accidents and effluents associated with the nuclear fuel cycle.Aquatic filter-feeders can capture and potentially retain radioactive particles, which could then provide concentrated doses to nearby tissues. This study experimentally investigated the retention and effects of radioactive particles in the blue mussel, Mytilus edulis. Spent fuel particles originating from the Dounreay nuclear establishment, and collected in the field, comprised a U and Al alloy containing fission products such as 137Cs and 90Sr/90Y. Particles were introduced into mussels in suspension with plankton-food or through implantation in the extrapallial cavity. Of the particles introduced with food, 37% were retained for 70h, and were found on the siphon or gills, with the notable exception of one particle that was ingested and found in the stomach. Particles not retained seemed to have been actively rejected and expelled by the mussels. The largest and most radioactive particle (estimated dose rate 3.18±0.06Gyh−1) induced a significant increase in Comet tail-DNA %. In one case this particle caused a large white mark (suggesting necrosis) in the mantle tissue with a simultaneous increase in micronucleus frequency observed in the haemolymph collected from the muscle, implying that non-targeted effects of radiation were induced by radiation from the retained particle. White marks found in the tissue were attributed to ionising radiation and physical irritation.The results indicate that current methods used for risk assessment, based upon the absorbed dose equivalent limit and estimating the “no-effect dose” are inadequate for radioactive particle exposures. Knowledge is lacking about the ecological implications of radioactive particles released into the environment, for example potential recycling within a population, or trophic transfer in the food chain.

Optimal allocation of bioassays in the case of parametrized covariance functions: an application to Lung’s retention of radioactive particles

In this paper, we investigate the effect of employing a parametrized covariance function in a regression experiment on corresponding optimum designs. We demonstrate these effects in the framework of a real example for measuring the lung’s retention of radioactive particles. Also, two different covariance functions are considered, and it is shown that this choice can play a crucial role.

Evaluation of the Clearance of Particles Deposited on the Conducting Airways of Beagle Dogs

ABSTRACT The new respiratory tract dosimetry model of the International Commission on Radiological Protection incorporates long-term retention of radioactive particles in conducting airways in its ...

Location and duration of retention of radioactive particles in mice.

A method is described by which the location and the duration of retention of inhaled particles were recorded under physiologic conditions by the exposure of mice to a radioactive aerosol, the mice being subsequently sacrified, sectioned, and autoradiographed. The distribution of the aerosol is discussed. (auth)

Location and Duration of Retention of Radioactive Particles in Mice

Location and Duration of Retention of Radioactive Particles in Mice