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Natural Remediation of Mines after Uranium Leaching

#K-622


Assessment of Ore-Containing Aquifers Natural Remediation after Uranium in-situ Leaching in Conditions of Shu-Sarysu Uranium-Ore Province

Tech Area / Field

  • ENV-RED/Remediation and Decontamination/Environment
  • ENV-MIN/Monitoring and Instrumentation/Environment

Status
3 Approved without Funding

Registration date
30.10.2000

Leading Institute
Volkovgeologia Joint-Stock Association, Kazakstan, Almaty

Collaborators

  • COGEMA / BUM/DT/MQSE, France, Velizy

Project summary

Main part of Kazakhstan industrial uranium reserves is concentrated in Shu-Saryssuiskaia uranium-ore province . Deposits are intensively mined out by acid in-situ leaching method. Mining facilities take necessary measures for ground waters protection at stage of operation and observe of residual solutions spreading after separate blocks and beds mining out is completed. Taking into consideration of that many uranium deposits are operated for 15-20 years on projects which have not practically been renewed so it should be expected some discordance between the projects and modern requirements which were changed two times for last time. Besides more many developments have become for environment safety. Therefore the project is proposed to assess sufficiency of the nature-safe measures, proposed by the projects and used in practice and to estimate a role of natural processes come after completing processing in blocks of IS-leaching sites.

At present, three uranium in-situ leaching mines with annual capacity up to 1200 tones of final product operate on territory of the Republic of Kazakhstan. Mining can be increased in case of foreign investments attraction. 5 uranium deposits are being mined out simultaneously, some other are planned to be developed. From the beginning of operation number of mined out beds and blocks amount to some tens, therefore there is a necessity to take measures for ground waters protection. Uranium in-situ leaching causes significant hydrodynamic and hydrochemical disequilibrium in surrounding media.

Organizations planning in-situ leaching polygons not always take into consideration some features of uranium deposits certain sites. Therewith, ecological and sanitary norms are constantly tightened, so comparison and analysis of spent polygons contaminated parts conformity to ecological conditions are urgent and advisable. Investigation results will be a base for planning organizations when they choose measures for ground waters and environmental protection of uranium deposits being mined out.

During two years the presented project will be carried out in three stages:

The first stage (two first quarters) is collection, generalization and analysis of information on operating mining companies, a choice of the sites for realization of the project and correction of it.

The second stage (following four quarters) is drilling and complex study of well core, and detail study of hydrological parameters in exploited ore bodies and blocks.

The third stage (final two quarters) is laboratory and computer modeling of solution spread, performance of analytical work and making-up the final report on the project.

In the first stage aims, tasks and methodology of forthcoming field investigations will be verified that is impossible without fulfilling the next row of jobs:


1.1. Collection and generalization of available information in JSC "Volkovgeologia" and mining companies accumulated since 70-th to now;
1.2. Analysis of gathered information especially on observations at groundwater regime within closed and operated in-situ leaching sites;
1.3 Drawing of maps, schemes and cross-sections, treatment of data from available monitoring hydrological wells for studying migration of elements in residual solutions;
1.4. Choice of blocks have produced for farther study, drawing expected cross-sections, making-up of technical tasks for drilling of each research well;
1.5. Correction of the initial project.

Collection and generalization of available information will provide fullness of data about studied sites and then enhance quality of outcomes of all forthcoming stages.

Analysis of gathered data would allow determining most characteristic peculiarities of physical-chemical processes going on groundwater after completing IS-leaching uranium production.

Drawing of maps, schemes and cross-sections visualizes outcomes of analysis that facilitates a comprehension of these outcomes.

Maps, schemas and cross-sections of a chosen block for investigations will become the base for a correction of forthcoming stages of investigations.

The correction of the present project will heighten its efficacy and quality.

In the second – field – stage there ill be received some factual data according to physical-chemical, epigenetic processes going on in groundwater both within a technogenic halo of distribution of residual sulfuric solution and beyond it in the result of the following types of jobs:


2.1. Drilling of research wells; 2400 m;
2.2. Making-up of core documentation, sampling of mineralogical samples and monoliths in intervals undergone and non-undergone by influence of productive and residual solutions; 160 mineralogical samples and monoliths;
2.3. Performance of outflow (pumping-out) and sampling of water from available monitoring set of hydrological wells; 80 watery samples;
2.4. Performance of laboratory and analytical work; more 240 analyses;
2.5. Treatment of field and laboratory information.

Each job of the stage decides the following tasks:

Drilling of 6 wells (2400 m) will allow to unseal rocks of an ore horizon exposed under sulfuric solution as 180 m of core will be upheld.

Making-up of core documentation allows to mapping petrographic and epigenetic peculiarities of the core within the technogenic halo and beyond it. It will be expected also that pH measurements on the core reveal residual phenomena of technogenic oxidation and recovery processes. The geologists who study the core will make purposeful sampling for mineralogical-petrographic investigations and laboratory tests.

Performance of outflow (pumping-out) and sampling of water from available monitoring set of hydrological wells within blocks, unsealed by research wells, will help to compare hydrological and geological data and decipher recovery processes by using samples of water for laboratory tests and data of samples for some computer calculations.

Performance of laboratory and analytical work will allow assessing size of grains and petrographic and mineralogical composite in rocks investigated and common composite of water through the technogenic halo.

Treatment of field and laboratory information will allow to make some preliminary outcomes:

  • the extent of redistribution of mineralogical-petrographic associations within the technogenic halo;
  • some basic agents of mass-transmission within the technogenic halo;
  • sorptive capacity of rocks within technogenic halo and beyond it;
  • the level of residual radioactive and chemical pollution of groundwater;

the extent of natural recovery of rocks within the primary contour of influence of sulfuric solution.

In the third – completed – stage computer and laboratory models will be adopted for studying and elucidating recovery of rocks exposed under sulfuric solution and upheld after several years of completing IS-leaching uranium production. The stage will give some verified outcomes of field and laboratory investigations, the outcomes and results of previous investigations will have been used for a prediction of the period of full natural recovery of rocks exposed and decreasing impact of subsequent IS-leaching uranium production on environment.


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