Dulaan Uul ISR Test
COGEGOBI carried out an in-situ recovery technology test at the site of the Dulaan Uul between December 2010 and June 2011, with the authorization of the Mongolian Nuclear Energy Agency and the Mongolian Ministry of Environment and Green Development. This test concluded that uranium can be mined with the ISR method at the deposit.
The performance of on-site testing is part of the legal requirement in Mongolia. The test results and the related environmental reporting are submitted to the Mongolian state authorities for each annual work.
ISR testing – a legal and operational requirement
ISR is the technology selected by COGEGOBI to fulfill the requirement by law to register the geological exploration of uranium reserves.
Testing is also needed to accurately determine the specifications of the future pilot production facility. In general, it is low-grade deposits with suitable geological characteristics that favor the use of ISR technology.
A two-cell wellfield to test the technology
A wellfield with 2 cells was constructed in order to carry out the ISR test. The cells are hexagonal, with injection wells in each corner and a production well in the center. The mineralization tested is 10 meters thick. A full-scale wellfield can contain up to 600 of these cells, as at KATCO’s mining site in Kazakhstan.
How does the ISR test work?
- The leaching solution is prepared by circulating groundwater through the facilities and adding a small amount of sulfuric acid.
- This leaching solution is then injected into the ore body.
- The leaching solution permeates the mineralized sand.
- Uranium in the mineralized body gradually dissolves in the solution, causing the latter to become saturated with uranium.
- The production well in the center of the cell pumps the uranium-rich solution back to the surface.
- The uranium is then transferred to the ion exchange columns, where it is recovered through adsorption using ion exchange resins.
“Ion exchange” refers to the process in which the ions in the solution are adsorbed onto the resins.
Supervision and environmental monitoring before, during and after testing
In order to monitor the hydrodynamics and quality of the groundwater layer, monitoring wells are positioned at the upper and lower levels of the layer and inside and outside the cells.
In order to work out the potential impact of the leaching process on the environment, and more specifically on groundwater quality, regular groundwater sampling and analysis are carried out both during and after the test period, according to the test program.
In this case, analysis and monitoring results showed that uranium could be recovered with very limited impact on the environment.
AREVA Mongol has reported the environmental impact results of the ISR test to the relevant Mongolian administrative bodies, along with its post-test environmental impact assessment.
DID YOU KNOW ?
The laboratory for hydraulic and chemical analysis built in the test site monitored daily the concentration of uranium, iron and acid, neutral environment, concentration of salt and other criteria. Over 400 analyses are made weekly during the test.
Re-use of the leaching liquid
After the uranium has been removed from the solution, the used solution is transferred to the unit that regulates the flow of the solution.
Sulfuric acid is added to the solution (concentration < 1%) and the solution is injected again through the injection well. The leaching process takes place in a closed circuit, but a small amount of the used water from the resin adsorption section, laboratory and the acid section is stored in the pool, which is constantly supervised.
The test results and next steps
Successfully completing the ISR test was an important stage in the transition from exploration to mining project development. The ISR test completed in June 2011 proved that uranium can be mined from the Dulaan Uul deposit using in situ recovery technology. Since these results were obtained, COGEGOBI has been working alongside its partners to launch the mining project.