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Speciation of artificial radionuclides in soil

#K-2274


Study of artificial radionuclides speciation in soil and their transformations

Tech Area / Field

  • ENV-EHS/Environmental Health and Safety/Environment
  • ENV-MRA/Modelling and Risk Assessment/Environment

Status
3 Approved without Funding

Registration date
09.02.2016

Leading Institute
National Nuclear Center of the Republic of Kazakstan / Institute of Radiation Safety and Ecology, Kazakstan, Kurchatov

Collaborators

  • Norwegian University of Life Sciences, Norway, As

Project summary

The proposed project seeks to study physical and chemical forms of major long-lived artificial 137Cs, 90Sr, 241Am and 239+240Pu radionuclides in soils, transformation of radionuclide speciation through time and their distribution in particle size, mineral and organic soil components. Study of speciation of radionuclides in soil is necessary to solve ecological problems, to predict a radionuclides intake into different adjacent environment from soil, as well as to develop scientific bases for radiation safety improvement and rational using of natural resources.

In the course of project implementation work within the following tasks will be performed:


1. Determining physico-chemical forms of major long-lived artificial radionuclides in soils at sites with various radioactive contamination mechanisms.
2. Studying artificial radionuclides speciation dynamics in soils through time.
3. Studying radionuclides distribution in different soil components (particle-size fractions, mineralogical part, earth humus).
4. Researching into the impact by climatic factors on radionuclide behavior in soil.

Analysis of the state of affairs in the research areas showed that there is a number of papers dealing with the study of radionuclides distribution in particle-size soil fractions (Chernobyl, Fukushima, Krasnoyarsk mining and chemical combine, western Cumbria, Nevada nuclear test site and others) and their speciation. However, the lion’s share of these papers is devoted to studying 137Cs and 90Sr behaviour. Behaviour of transuranium radionuclides is still understudied. Only a few works concerning 239+240Pu distribution in particle-size soil fractions (Trinity nuclear explosions, ‘Rocky Flats’ nuclear weapons production plant and Los Alamos research laboratory) were found among available scientific literature. Review of world scientific literature produced no satisfactory results on 90Sr and 241Am distributions in particle-size fractions of soil.



It follows from the available data analysis on 137Cs distribution in particle-size soil fractions that in most cases 137Cs shows stability of behavior in various radionuclide intake mechanisms to soil. However despite the fact that the basic regularities of 137Cs behavior in soil are well clarified, prediction of transuranium elements behavior on their basis would be absolutely incorrect because these radionuclides have different physical-chemical properties and geochemical specifics.

Semipalatinsk test site is the most appropriate facility to study behavior of transuranium radionuclides. Firstly, a variety of performed nuclear tests caused the presence of different mechanisms of radionuclides intake to soil at its territory and corresponding to them objects-analogs with various quantitative and qualitative compositions of radionuclide contamination. An important factor is also an opportunity to study the behaviour of 239+240Pu and 241Am transuranium radionuclides in environment objects. Secondly, all the STS objects are located in the same climatic and soil zone which could allow to minimize influence of external environment factors on radionuclides behavior. Thirdly, study of radionuclides speciation in soil using identical methodological and analytical approaches will make it possible to carry out comparative data analysis correctly and to reveal peculiarities of radionuclides behavior under various conditions of their intakes.

Novelty of the scientific researches proposed for implementation in this project is that the formation mechanisms of artificial radionuclides (137Cs, 90Sr, 239+240Pu и 241Am) distribution between soil particle-size fractions and nuances of their behaviour under different conditions of radioactive contamination will be revealed. In addition, a new approach of differentiation of intake mechanisms will be applied instead of tying to certain radioactively contaminated objects as was accepted before. STS objects (testing grounds, venues of nuclear tests) will only be used as objects-analogs corresponding to one or other type of intake mechanism.

In addition, in case of successful implementation of the project, one-of-a-kind experimental data for transformation on radionuclides speciation through time and impact of climatic factors on their behavior in soil will be obtained. Peculiarities of distribution of radionuclides in mineral and organic soil components will be revealed which allow organization of safe mining operations to be improved and use of natural resources to be rationalized.

Branch 'Institute of Radiation Safety and Ecology’ of the National Nuclear center of the Republic of Kazakhstan disposes of modern measuring equipment allowing high-accuracy analyses of natural and agricultural objects to be made for concentrations of radionuclides, heavy metals, micro- and macro-elements. Scientific units of the Institute are equipped with all required equipment and materials (laboratory equipment, instruments, reagents) for undertaking cytogenetic, morpho-physiological studies as well as for assessing agrochemical and physicochemical soil properties.



In the course of the project implementation both field observations of artificial radionuclides distribution among bioavailability forms, particle-size, mineralogical and organic soil components under different intake mechanisms and experimental studying transformation of radionuclides speciation through time and resistance of radioactive particles to impact of climatic factors will be carried out. Objects-analogs of STS corresponding to different mechanisms of radionuclide intake into soil by type of radioactive contamination will be selected.

In the course of undertaken studies the following results will be obtained:


- peculiarities in radionuclides distribution among different forms of their bioavailability and particle-size soil fractions have been revealed at various mechanisms of radioactive contamination;
- experimental data for transformation of radionuclides speciations through time;
- data about radionuclides distribution in components of mineral and organic soil substances;
- resistance of soil radioactive particles to the effects of climatic factors and change in radionuclide mobility at their various dispersiveness.

Findings can be used during environment impact assessment (EIA) of the marked objects whose activities assume possible radioactive contamination of the environment; when estimating and/or predicting the risk of existing radioactive contamination caused by migration of radionuclides in the ‘soil-plant’ system, air basin contamination and inhalation hazard to man; to improve organization of safe mining operations and rationalizations of natural resources utilization.


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