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Radiation Risks in Atmosphere-Surface System

#K-928


Integrated Study of Radioactive Contamination of Atmosphere-Underlying Surface System and Assessment of Radiation Risks for Population of Semipalatinsk Region

Tech Area / Field

  • ENV-EHS/Environmental Health and Safety/Environment

Status
8 Project completed

Registration date
23.09.2002

Completion date
16.02.2009

Senior Project Manager
Rudneva V Ya

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

Collaborators

  • Claremont McKenna College, USA, CA, Claremont

Project summary

Nuclear tests and nuclear accidents as well as wide application of nuclear power and man-made radionuclides in different areas of the human activity caused several releases of a number of radioactive elements into the environment. These elements differ in physico-chemical and nuclear-physical forms.

Initially, the application area of the man-made radionuclides was limited to scientific research. However, already in early 1940s, due to invention and development of nuclear weapons, a large industrial branch dealing with generation and use of radionuclides developed. Since 1945, numerous tests of nuclear devices expanded the habitat of artificial radionuclides and included them into various natural cycles: biochemical, hydro-chemical, geo-chemical, atmospheric, etc. All these cycles are closely related to each other, therefore, the primary scientific tasks, under present conditions, are to carry out an integrated study of man-made radionuclides and forecast their behavior in the environment.

The basic sources of so-called technogenic radionuclides are nuclear weapon tests. The radioactive contamination caused by these tests is mainly due to nuclear fuel fission fragments, non-reacted nuclear fuel, and products of neutron activation of structural materials and environment. However, the long-lived 90Sr, 137Сs, 239,240Pu and some other radionuclides pose the greatest hazard to the environment and man with time.

Following the deposition, in any form, onto the ground surface, the radionuclides can be redistributed and transferred by wind and surface and ground waters. Obviously, the radionuclide migration rate and transfer to the food chain, and ultimately into a human body, first of all depends upon the chemical species of radionuclides that determine their solubility. The chemical form of radionuclides present in a release can vary from relatively insoluble oxide particles to readily soluble inorganic salts and organic complexes. However, the initial form of released particles becomes less important with time. The initial chemical and physical properties of particles can undergo various changes due to the influence of a series of processes, such as chemical weathering, erosion, mechanical impact, biological transformations, radiolythical processes, etc. These changes affect the radionuclide behavior. Therefore, it is necessary to study the variety of migration pathways and processes that the long-lived radioactive products of nuclear explosions are involved in according to the following scheme: highly contaminated objects and soils of the former STS sources of long-lived radioactive products’ release into the atmosphere the atmospheric transport of radioactive products subsequent deposition of the radioactive products onto the underlying surface. The following will be generated:

– Data on rates of radionuclide releases to the atmosphere and atmospheric transport of airborne particle dredges, biologically available radioactive fallout fractions (BARFF), and inhaled aerosols.

– Estimates of 90Sr, 137Cs, 239+240Pu and 241Am distribution by the radioactive particle size.

– Data on bulk concentrations of the above radionuclides in the near-surface atmosphere within areas of control observations and particular attention should be paid to BARFF and aerosol radioactive particles deposited in lungs. It is known that studies carried out by K.I. Gordeev, L.A. Il’in, A.N. Lebedev, and S.M. Shinkarov from RF SSC Institute of Biophysics and by E.C. Land, A. Buville, and N. Luk’yanov from the US Institute of Cancer showed that the scientific conception of the biologically available fallout fraction is a basis for realistic assessment of the population internal exposure due to environment contamination by the radioactive fallout. Under present conditions of the former STS the radioactive particles that cause intensive deposition of these particles’ fraction in control observation areas can get to the atmosphere during strong winds due to the wind erosion of the topsoil especially during fires. The US Governmental Program on Assessment of the Population Radiation Doses and the Nuclear Explosion Radioactive Fallout Impact on the Population Health demonstrates the importance of the BARFF conception. As for the radioactive aerosol deposition in lungs, this deposition type determines the inhalation pathway of 90Sr, 137Cs, 239+240Pu and 241Am intake that should be also taken into account when assessing the radiation risks.

– Data on bulk concentrations of toxic metals, beryllium and dust in the atmospheric air to compare the radiation risk and non-radiation risks caused by the above elements.

Besides, in order to forecast the radionuclide behavior in the environment it is needed to study the radionuclide forms as after their deposition onto the ground surface as well as in the course of their continuous presence on it. The data will be obtained necessary to carry out representative assessments of medical and biological effects of the processes under study.

The objective of the present project is to perform an integrated study of the radioactive contamination in the system “atmosphere – underlying surface” and assess the radiation risks for population of the Semipalatinsk area. The work program of the present project envisages fulfillment of the following tasks:

1. Analyze the archival information available on atmospheric tests conducted at the Semipalatinsk Test Site; perform a retrospective analysis of and generalize data obtained so far on physical, physico-chemical and nuclear-physical characteristics of radioactive particles including biologically available fractions of nuclear test aerosol products deposited onto the STS ground.

2. Collect, analyze and generalize data obtained in the course of observing the seasonal changes in the underlying surface and density of the vegetation cover at the former STS, data on recurrence of sandstorms and other weather events, and data on vegetation radioactive contamination in areas of planned field monitoring.

3. Develop procedures for field sampling and laboratory analysis of radioactive formations and particles. Study the radionuclide distribution in granulometric soil fractions. Survey the areas contaminated by plutonium and americium using FIDLER and in situ gamma spectrometry with detectors of higher resolution.

4. Identify physico-chemical properties of radioactive particles and formations and determine their solubility in different natural media and their ability to transfer to exchangeable forms.

5. Arrange and carry out field investigations to study the variety of migration pathways and processes in the system “atmosphere – underlying surface” at the former STS using the following scheme: soil dust resuspension – atmospheric transport – deposition of the radioactive products onto the underlying surface – contamination of plants.

6. Assess the radiation risk for critical population groups residing the areas affected by the Semipalatinsk Test Site, based on a model of multiple pathways of the radioactive contamination.

Basic Anticipated Results:

– Analysis of the archival information on atmospheric nuclear tests at the Semipalatinsk Test Site (STS) will be performed, data obtained so far on physical, physico-chemical and nuclear-physical characteristics of radioactive particles including the biologically available fractions of nuclear explosion aerosol products and radioactive fallout particles at the STS.

– Data obtained in the course of observing the seasonal changes in the underlying surface and density of the vegetation cover at the former STS, data on recurrence of sandstorms and other weather events, and data on vegetation radioactive contamination in areas of planned field monitoring will be collected, analyzed and generalized.

– Procedures for field sampling and laboratory analysis of radioactive formations and particles will be developed. The areas contaminated by plutonium and americium using FIDLER and in situ gamma spectrometry with detectors of higher resolution will be surveyed.

– Physico-chemical properties of radioactive particles and formations will be identified and their solubility in different natural media and their ability to transfer to exchangeable forms will be determined.

– Field investigations will be arranged and carried out to study the variety of migration pathways and processes in the system “atmosphere – underlying surface” at the former STS using the following scheme: soil dust resuspension – atmospheric transport – deposition of the radioactive products onto the underlying surface – contamination of plants.

– Generalized data on basic physical characteristics and physico-chemical parameters of the radioactive contamination processes occurring in the system “atmosphere-underlying surface” due to radioactive particles of terrigenic airborne dredges, biologically available radioactive fallout fractions and inhaled aerosols (especially at fires) will be obtained. The data will be used as a basis for assessment of radiation risks for population of the Semipalatinsk area and the following recommendations.

All the components of the present project directly meet the ISTC objectives and goals as they:

– provide an opportunity for IRSE specialists previously involved in development and testing of nuclear weapons to be engaged in peaceful research activities;


– support applied research for peaceful purposes and environment protection;
– assist in solving such national and international technical problems such as control of radiation and ecological situation in areas of enhanced radiological risk (nuclear weapon test sites, radioactive waste repository sites, NPP).

The role of collaborators involved in the project implementation will include:

– review of reporting materials;


– statement of remarks and comments;
– discussion of reporting materials;
– joint development of methodical approaches;
– identification of directions for further study;
– support of arrangement of regional workshops;
– provision of information useful for project implementation.


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