Sources and Types of Uncertainties Associated with Radioactive Particles

Abstract

Abstract:The environmental release of radionuclides associated with hot particles is more frequent than commonly recognised, and should also be expected in future nuclear events. Hence the presence of radioactive particles can be expected to influence the environmental impact and risk assessments associated with contaminated areas. This paper addresses the different types of uncertainty arising from hot particles. The first part considers the different categories and dimensions of uncertainty, and the second part illustrates the way that hot particles can impact on the source term, transfer, and biological effects of radionuclides. While it is certainly not the case that increased knowledge will always result in reduced uncertainty (for example the presence of hot particles can lead to greater variability in parameters), it should be clear that assessments will benefit greatly from a better understanding of the way hot particles can impact on the behaviour of radionuclides in the environment.

The nature of Pu-bearing particles from the Maralinga nuclear testing site, Australia

“…We use the new information to (i) decipher the mechanisms that led to the formation of hot particles with highly complex and varied internal make-up at Maralinga; (ii) revisit the evidence for on-going weathering processes affecting Pu and U in the hot particles; a direct comparison of differential weathering of Pu and U is made possible by the fact that both actinides coexist in these particles; and (iii) explore the pathways for long-term (decades to 100’s of years) Pu release from the hot particles. The Maralinga particles are models for hot particles released during subcritical nuclear incidents, and are also useful in nuclear forensics as proxies for those generated from dirty bombs 8 . Overall, these new results corroborate that particle inhomogeneity and morphology 1 , 2 , 9 are as or even more important as the speciation as determinants of the fate of U and Pu in the environment, and demonstrate that the accuracy of predictive models depends on the inclusion of these parameters obtained from experimental measurements.…”

Vadose-zone alteration of metaschoepite and ceramic UO2 in Savannah River Site field lysimeters

“…Intact UO 2 particles have been isolated from numerous contaminated sites, often originating from nuclear fuel material (e.g., Kashparov et al, 2019;Ochiai et al, 2018). Although UO 2 particles have been shown to persist in the environment for many years (Oughton and Kashparov, 2007), oxidative dissolution and subsequent migration of U through the geosphere is possible, with UO 2 forming secondary U(VI) phases, such as metaschoepite (UO 3 •nH2O), under oxidizing conditions (Buck et al, 2004a;Finch and Ewing, 1992). Indeed, the production of metaschoepite colloids from UO 2 powders (44-105 μm) has also been reported following exposure to aerated deionized water, and aged metallic depleted uranium munitions are known to form metaschoepite as a major corrosion product (Buck et al, 2004b;Handley-Sidhu et al, 2009;Wang et al, 2016).…”

A Highly Efficient Biomass Compound Aerosol Suppressant in Purifying Radioactive Cesium Droplet Aerosols

“…The radioactive aerosol is a stable colloidal system consisting of solid or liquid particles of radionuclides which are dispersed and suspended in a gas phase environment [ 1 , 2 ]. A great number of radioactive aerosols will be inevitably generated from the nuclear fuel cycle, radioactive waste disposal in the nuclear industry, nuclear weapon tests, discharges from nuclear installations, and nuclear accidents [ 3 , 4 ], such as the Fukushima nuclear accident which leaked 137 Cs radioactive aerosols [ 5 ]. In addition, during the discharge process from nuclear installations such as the decommissioning and decontamination (D&D) of nuclear power plants, it is easy to produce a large amount of radioactive aerosol with high mass concentration to the air and that brings a greater risk of internal exposure to workers, especially when they work in chamber places where radioactive aerosols can be easily accumulated, such as equipment rooms, etc.…”