VNIPIpromtekhnologii JSC, Moscow, Russia:

D. V. Maynikov, Head of Laboratory, Candidate of Technical Sciences, e-mail: didima06@mail.ru
E. P. Bugrieva, Lead Researcher

Khiagda JSC, Chita, Russia:
E. A. Gurulev, First Deputy General Director – Chief Engineer
A. V. Suvorov, Principal Geologist – Group Leader

Khiagda JSC is a leading Russian producer of uranium that relies on in-situ leaching. Currently, the company is developing several uranium deposits, including the Khiagda deposit launched in 1980. Over the years, however, the efficiency of recovering the commodity product from the Khiagda ores has dropped significantly. Experts from VNIPIpromtekhnologii JSC have conducted a series of studies aimed at defining the reasons of uranium under-recovery and finding ways to intensify the ISL process. A mineralogical study of core samples taken from Block X-7 of the Khiagda deposit did not reveal any secondary mineralization of uranium in the rock mass. The under-recovery of uranium might be attributed to the presence of its sorbed form in the poorly permeable clay rock and titanium-enriched amorphous gel, the development of which would require a harsher environment and a longer time. The subsequent geotechnical study indicated that the mean recovery of uranium from the core samples in laboratory conditions when using the Khiagda JSC leach solution is ~55%. When the acidity of the leach solution is raised to the H₂SO₄ concentration of 20 g/dm³, the recovery rises to 74.4%. A further study carried out in a continuous filtration mode showed that, due to the use of a leach solution with the concentration of sulphuric acid raised to 20 g/dm³, as much as 95.6% of uranium can be transferred to the solution, the leaching time can be reduced by 36.8%, the concentration of uranium in the pregnant solution can be raised by approximately 1.6 times and the total volume of the solutions can be reduced by 2.3 times. A feasibility study that used the obtained results to look at possible substitution of the normally used leach solution with the proposed one showed that with the proposed leach solution the development costs would drop by 75.6%, while the total discounted cash flow would amount to ~6.5 bln roubles.
The authors would like to express their deep appreciation and gratitude to Anatoly N. Mikhaylov, general director of Khiagda JSC, for his support of this publication.

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