"Hot" Radioactive Particles
Research and Systematization of "Hot" Particles in Former Semipalatinsk Nuclear Test Site Soils
Tech Area / Field
- ENV-RED/Remediation and Decontamination/Environment
8 Project completed
Senior Project Manager
Bunyatov K S
National Nuclear Center of the Republic of Kazakstan / Institute of Nuclear Physics, Kazakstan, Almaty
- European Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe\nLos Alamos National Laboratory / NIS-7 Safeguards Systems Group, USA, NM, Los-Alamos
One of the less studied forms of artificial radionuclide existence in the environment are the so called "radioactive" particles – compact formations with a substantial level of specific radioactivity.
There are different types of "radioactive" particles, one of which is connected with the sites of nuclear tests and another with "radioactive" particles of global fallout. The first type exceeds the second in both quantity and size (by up to several mm), the sizes of which make up constitute portions and unit microns. Respective distinctions are also observed, as a rule, in radioactivity levels. At the same time, a number of literary sources note that data on "radioactive" particles in the vicinity of test sites provide the grounds for inferences on origin and properties of "radioactive" particles, falling at a high distance from the place of explosion, the main basis of the need for a study of "radioactive" particles at the SNTS.
It is well known that the formation of "radioactive" particles at explosion sites takes place as a result of changing temperature and complicated thermodynamical and nuclear-physical processes, occurring in the fiery sphere and nuclear explosion cloud. Academician Y.A. Israel substantially contributed to the development of modeling methods, defining the state of radionuclides in the fiery sphere and the subsequent formation of "radioactive" particles for explosions of different power and type. A significant volume of experimental material on "radioactive" particles, generally global, has been collected by Russian specialists when studying meteorological aspects of radioactive contamination spread. Highly detailed studies of the "radioactive" particles’ radionuclide mixture, directly at the sources of explosions, and at different distances from them, (including global fallout) are conducted by scientists and specialists of the USA, in relation to nuclear explosions at the Nevada test site.
The considerable lack of available data on the current radio-ecological situation, due to long-lasting and various nuclear tests at SNTS, is the result of a lack of systematized data on "radioactive" particles at the test site. Most probably, there is much in common with the data from the test site in Nevada.
At the same time, notwithstanding the considerable commonness of the tests, there are many discrepancies, both in the kind and power of nuclear explosions, the structure and nuclear construction materials of explosive facilities and in meteorological terms of conducting explosions, and in the structure of underlying and containing soil at the places of conducting surface, excavation and subsurface explosions. Undoubtedly, these circumstances, in their specificity, lead to forming processes and, therefore, to the structure and compound of "radioactive" particles.
We conducted separate studies of the radionuclide compound and content in fractions of soil within the framework of Project К-053-96. For the different fields of SNTS, differences in both concentrations and in distributions of radionuclides in soils fractions were determined. So, for example, at sites closer to the epicenter of nuclear explosions, the main activity of radionuclides, especially of plutonium and americium, represents a larger (1-3mm) proportion. At approximately 20km from an explosion epicenter, 137Cs is amassed in a rather large fraction, whereas 70% 241Am is in a fraction with a particle size of 0.1 – 0.3mm. At that, it is determined that 90% of 241Am and 60% of 239Pu are in a magnetic fraction conditioned by the presence of ferromagnetic phases with a high content of iron and almost no 137Cs.
At areas near the fields of excavation nuclear explosions, 137Cs and 241Am are contained mainly in fractions smaller than 0.3mm. In estuary fields of mining the Degelen Massif, the radionuclides are massed in different fractions: from small fractions and up to 1.25mm. These results are obtained on the basis of episodical analysis and indicate the need for a detailed experimental study of the radionuclide fractionating degree and radionuclide compound in the soil’s radioactive particles, at areas near the sites nuclear explosions and local traces of radioactive fallout over the territory of SNTS.
The aim of this project is a thorough study of the characteristics of SNTS soil "radioactive" particles, their classification and systematization on nature, phylum and power of atomic explosions, and evaluation of the risk level owing to "radioactive" particles of different phylum.
The project envisions solution of the following three problems:
1. Study of "radioactive" particle structure and compound, singled out from soil samples of different SNTS areas;
2. Evaluation of radionuclide migratory properties from "radioactive" particles under the effect of various natural factors;
3. Classification and systematization of "radioactive" particles according to their character, phylum and power of conducted tests and evaluation of the risk level in view of "radioactive" particles of various phylum.
When solving these problems, main plants of INP NNC RK (reactor WWR-K, cyclotron Y-150, linear accelerator UKP-2), modern measuring equipment and a large arsenal of physical, nuclear-physical, chemical and radiochemical methods of investigation will be used:
screen and sedimentary analysis;
radionuclide analysis (instrumental and radiochemical) for determination of 137Cs, 239+240Pu, 241Am, 90Sr, 60Co, 152Eu, 154Eu, and etc. compound in various soil fractions and in "radioactive" particles:
radiography, fission tracks;
activation and Roentgen fluorescent analysis;
electron and optical microscopy;
Mass-spectroscopy and others.
The project stipulates the elaboration of a common investigation methodology, including sampling of dignified samples of soil from the sites of surface nuclear explosions, excavation nuclear explosions and spare nuclear explosions, and estuary areas of the Degelen Mountain massif adits. Studies will be made of the selected samples, using the common technology, including:
study of artificial radionuclide distribution on various granulometric fractions by application of wet sifter;
separation of magnetic component from each fraction;
study of 239Pu, 241Am and 137Cs fractionating degree in radioactive particles by application of instrumental gamma-spectrometry;
determination of "radioactive" particles in selected sub-fractions by application of auto-radiography or fission tracks;
comparative quantity analysis of "radioactive" particles in different fractions and samples;
study of radionuclide discharge from "radioactive" particles and various fractions by fractional leaching;
study of the structure and elemental compound of "radioactive" particles, using activation analysis, scanning electron microscopy and micro-PIXE;
study of the transuranium element isotope compound of the "radioactive" particles, using mass-spectroscopy;
study of radiation defects in the "radioactive" particles, using EPR-spectroscopy;
study of the magnetic properties of the "radioactive" particles and soil separate fractions, using various methods.
The results of these investigations allow one:
to reveal general rules and certain peculiarities of radionuclide fractionating, depending on the different phylum of nuclear tests;
to determine specific signs of "radioactive" particles and their systematization in the context of the investigation of territories used for nuclear tests;
to develop methods of numerical determination of the amount of "radioactive" particles in soil;
to evaluate the concentration of radionuclides;
to study the regularity of the radionuclides, "radioactive" particle propagation and their transformations;
Thus, the results attained in the course of the Project will help to attain a more complete picture of the radio-ecological situation at SNTS and to give an objective value and level prognosis of its radiation danger.
At the same time, the attained, highly-detailed data on structure and compound of the "radioactive" particles can be quite useful for specification of the processes arising from a fiery sphere when conducting explosions of various phylum.
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