There is a universally recognized opinion that thorium has a low chemical solubility and forms poorly soluble compositions in natural environment, that it has highly selective sorbing with contrast on physico-chemical properties and mechanical composition soils and does not migrate with natural water, mudflows or flood water. However in some researches (for example, Collection of papers “Chemical researches of rare- and accompanying elements”, AN Kyrgyz SSR, Frunze, 1966, article of Yakovenko R.T. and Mustaev A.K. “Study of systems Th(NO3)4 – K2P2O7 – H2O at 26 C”. P. 82) it is shown that thorium in a process of its acid and alkali-nitrate release from natural raw materials and further storage in tail deposits and sewage tanks forms well soluble double salts with alkali metals. These double salts as well as soluble salts of thorium, rare-earth elements and heavy metals formed at interaction with atmosphere precipitation, containing rocks biota and its life activity and metabolism products can migrate and pollute the environment.
So, for instance, in 1964 at former Aktyuz Mining enterprise of Kyrgyz Mining Metallurgical industrial complex and at Kyrgyz Chemical and Metallurgical works an accident took place: the dam was destructed and sands with high thorium concentration got in rivers Kichikemin and Chu. The researches of soils nearby the Chu river in territory of Kazakhstan made in 2002 showed increased content of thorium, its decay products and other toxins, characteristic for rare-earth production. Accumulating industrial sewage tanks of Kyrgyz Chemical and Metallurgical works (vicinities of Orlovka village) as well as other enterprises of radioactive raw materials processing located near the Chu river are also potentially hazardous.
Goal of the Project:
The main goal of the project is the assessment of technogenic (man-caused) thorium-232 and radium-228 contribution in radiation background at locations of rare-earth raw materials mining and processing in Kyrgyzstan and the assessment of their influence on human and biota.
Technical Approach and Methodology:
Radionuclide, chemical, and elemental composition of natural and technogenic (man-caused) systems will be estimated within the frameworks of the Project. The samples of water (wells, springs, rivers, etc.), rocks (tail deposits, dumps), riverside soils and bottom sediments will be selected. For determination of the same components background contents the samples will be selected in control points located beyond the rare-earth production tail deposits and dumps affected zone.
The collected materials will be analyzed with the help of ?- and ?-spectrometry and other methods of heavy metals content determination.
Hydrogeological and hydrological investigation of locations under study will consist in assessment of water balance formation conditions and in calculation of parameters controlling surface and ground flow. These characteristics will be mainly obtained on the basis of the archival data analysis. Actualization of obtained characteristics will be made on the basis of monitoring of global tracers (environmental tracers) – stable isotopes (deuterium and oxygen-18) and tritium in atmosphere, surface and ground flows.
The parameters controlling thorium-232 and radium-228 migration will be determined both in laboratory conditions and as a result of on-site observations. The analysis of archival data and monitoring of thorium-232 and radium-228 and other components spreading will be made for selected locations during the project fulfillment.
Auxiliary isotope systems will be used for estimation a migration parameters in situ. A combined migration parameter in ground water, which integrates all conditions, is a retardation factor. It will be estimated by two methods: first, by comparing a rate of radionuclide contamination spread and a rate of neutral tracers (deuterium and oxygen-18) migration, determined during the project observations; second – by comparing a radionuclide contamination rate with water exchange rate estimated on tritium. For the project tasks solution the method which was developed during implementation of ISTC projects KR-072-97 and KR-715, KR-850, based on discovery of V.V. Cherdyntsev and P.I. Chalov “Phenomenon of Natural Separation of 234U and 238U” is also proposed. This method allows determining a share of technogenic (man-caused) uranium, i.e. assessment of technogenic (man-caused) impact on radionuclides contents in surface and ground water.
With the proposed methods it is possible to distinguish and to quantitatively estimate a share of natural and technogenic water of tail deposits (settlers), to build a apace picture of the tail deposits’ toxic water dilution as well as to solve other tasks concerning toxic ingredients water migration.
After mathematical models are developed, verified and calibrated, a predictive space picture will be built of technogenic water dilution to safe for the environment levels, a necessity of anthropological load abatement on the environment, technical and technological principles and methods for this will be defined.
Staff Competence.
All participants of the project are experienced in carrying out radiation, hydrogeological and isotope-chemical researches. The Project developers are leading experts in the field of filtration, water and air mass transport numerical modeling. The participants took place in other ISTC programs.
Expected results:
1. Verification of proposed methodology and development of practical technique and methods for tracing radioactive and rare-earth production waste migration with natural water.
2. Building of radionuclides and accompanying toxins space distribution at adjacent territories owing to their water migration from tail deposits and settlers;
3. Assessment of radioecological and toxic hazard.
4. Work out recommendations for monitored objects radioecological and toxic hazard mitigation.
5. Creation of mathematical models of migration of thorium, its decay products, and other toxins characteristic for rare-earth production.
6. Mathematical prognoses of thorium, its decay products and other toxins spreading in natural objects of the environment.
Role of Collaborators:
- Participation in organization of meetings, work out plans, establishment of relations with interested organizations;
- Rendering of assistance in acquiring technical means for realization of work under the Project;
- Participation in analytical work on inter-laboratory matching;
- Assistance in creation of database;
- Information exchange during the Project fulfillment, hold joint workshops, participation in International conferences and joint publications.
Scope of activities:
The assessment of technogenic thorium-232 and radium-228 contribution in radiation background of locations of rare-earth raw materials mining and processing will be made at implementation of the following stages of work.
1. Outlining of sites with increased concentrations of thorium-232 in water-containing rocks stipulated by technogenic (man-caused) activities.
2. Assessment of thorium-232 and radium-228 activity in surface and ground water at these locations.
3. Study of water balance structure, substantiation of conceptual and verification of quantitative hydrology-hydrogeological models of outlined sites.
4. Identification and quantitative assessment of processes resulting in formation of increased concentrations of thorium-232 and radium-228 in surface and ground water, building of respective thermodynamic and migration models.
5. Assessment of technogenic thorium-232 and radium-228 current contribution in radiation background and short-term prognosis of its change;
The planned researches agree with the ISTC goals because the project aims at conducting the researches on assessment and consequent recommendations work out for preventing negative aftermaths from chemical technologies impacts on the environment.
