The thermodynamic model of the in-situ leaching of uranium at the stage of acidification of the productive formation is considered. It is shown that at the front of promotion of acid leaching solutions, re-deposition of tetravalent uranium by redox processes involving ferrous ions is possible. To eliminate the negative effects, we suggested the use of artificial oxidants not only at the stage of active leaching of blocks, but also at the stage of active acidification of new technological cells. During the use of oxidants at the stage of acidification through filtration of discharge area to the unloading area solutions, the formation of technogenic geochemical zonation is possible. The use of sodium nitrite and air oxygen at the acidification stage will allow efficient preparation of an oxidizing productive horizon that will lead to shortening of the mining process unit, and hence to reduction of the production cost of uranium.