Morphology of actinide-rich particles released from the BOMARC accident and collected from soil post remediation

The plutonium isotopes and strontium-90 determination in hot particles by characteristic X-rays

This paper reports the developed non-destructive methods for the plutonium isotopes and strontium-90 content determination in hot particles and other samples. The proposed methods are based on the measurement of the characteristic X-rays accompanying the decay of these radionuclides. For hot particles of NPP accident origin, the proposed method's error limits are 10-15% for hot particles (samples) with activity above 100 Bq and 15-20% for hot particles (samples) with activity less than 100 Bq. For explosive particles, the determination accuracy is 10-15% for activity more than 5 Bq and 20-30% for 0.1-5 Bq activity. The accuracy of the proposed method for determining ⁹⁰Sr in samples with its specific content of more than 10⁴ Bq/sample is 5%, with ~10² Bq/sample its content is 15-20%. The cost of one sample measurement and the processing time of these methods are significantly reduced compared to traditional studies. The proposed methods are reasonably simple measurement methods and can be carried out even in the field condition. They open up new possibilities for the quick search and study of hot particles and environmental samples.

Review of technologies for preventing secondary transport of soluble and particulate radiological contamination from roadways, roadside vegetation, and adjacent soils

Transport of contaminants from roadways to the environment is well known, although studies of technologies for preventing and managing this appear infrequently in the literature. This paper reviews technologies studied for radiological contaminants. In addition to nuclear facility decommissioning, nuclear power plant accidents at Chernobyl (Former Soviet Union), Fukushima (Japan) and elsewhere have provided real world situations to both develop and test technologies to remediate radiological contamination and to return roadways, along with adjacent vegetation and soil, to prior use. From publications arising from these efforts, technologies were reviewed for radioactive material with two distinct properties (water-soluble and insoluble radioactive contaminants). The reported characteristics and capabilities of technologies are summarized in this review. This review also presents logistical considerations of implementation of the technologies, including waste management which can be an extreme impediment to rapid remediation if generated quantities of hazardous waste exceed local handling capacity. The summarized literature review suggests future avenues of work, chiefly for insoluble particulates, focused on technologies which may be mechanistically applicable to their remediation. While the underlying chemical and physical mechanisms that contribute to transport differ among contaminants, the studies reviewed here might also be applicable to non-radioactive contaminants, because the presence of radioactivity is largely independent of the underlying mechanisms.

Analytical techniques for charactering radioactive particles deposited in the environment

Since 1945, a series of nuclear and radiological sources have contributed to the release of radioactive particles containing refractory elements into the environment. Several years of research have demonstrated that the particle composition will depend on the source, while the release scenarios will influence particle properties of relevance for environmental transfer. Radioactive particles can also carry sufficient amount of radioactivity (MBq) and represent point sources of radiological concern. Most radiological assessment models, however, are based on bulk concentrations, assuming that radionuclides in the environment are evenly distributed. In contrast, radioactive particles and thereby doses are unevenly distributed, while leaching of radionuclides from particles prior to measurements can be partial, potentially leading to underestimation of inventories. For areas affected by particle contamination, information on particle characteristics controlling the particle weathering rates and remobilization of particle associated radionuclides will therefore be essential to reduce the overall uncertainties of the impact assessments. The present paper will focus on analytical strategies, from screening techniques applicable for identifying hot spots in the field, fractionation techniques and single particle extraction techniques as a preparatory mean to apply non-destructive solid state speciation techniques, till leaching techniques applied sequentially to obtain information on binding mechanisms, mobility and potential bioavailability. Thus, a combination of techniques should be utilized to characterize radioactive particles in order to improve environmental assessments for areas affected by radioactive particle fallout.

Multiscale Speciation of U and Pu at Chernobyl, Hanford, Los Alamos, McGuire AFB, Mayak, and Rocky Flats

The speciation of U and Pu in soil and concrete from Rocky Flats and in particles from soils from Chernobyl, Hanford, Los Alamos, and McGuire Air Force Base and bottom sediments from Mayak was determined by a combination of X-ray absorption fine structure (XAFS) spectroscopy and X-ray fluorescence (XRF) element maps. These experiments identify four types of speciation that sometimes may and other times do not exhibit an association with the source terms and histories of these samples: relatively well ordered PuO2+x and UO2+x that had equilibrated with O2 and H2O under both ambient conditions and in fires or explosions; instances of small, isolated particles of U as UO2+x, U3O8, and U(VI) species coexisting in close proximity after decades in the environment; alteration phases of uranyl with other elements including ones that would not have come from soils; and mononuclear Pu-O species and novel PuO2+x-type compounds incorporating additional elements that may have occurred because the Pu was exposed to extreme chemical conditions such as acidic solutions released directly into soil or concrete. Our results therefore directly demonstrate instances of novel complexity in the Å and μm-scale chemical speciation and reactivity of U and Pu in their initial formation and after environmental exposure as well as occasions of unexpected behavior in the reaction pathways over short geological but significant sociological times. They also show that incorporating the actual disposal and site conditions and resultant novel materials such as those reported here may be necessary to develop the most accurate predictive models for Pu and U in the environment.