**4. Conclusions**

Our studies showed that using the proposed approach results in a partial or full reduction of uranium, ammonium nitrate, and other compounds; distribution can be reached at all sites. While the production facilities are being operated, the injection of reagents for the sustainable development of the biogeochemical barrier should be carried out with a frequency sufficient to change the compounds into solid (U, S) as well as gaseous (N) phases. After decommissioning and preserving the facilities, it is necessary to provide for a margin of stability of barriers, thereby preventing degradation by background water, which will gradually replace contaminated technogenic solutions.

**Author Contributions:** Conceptualization, A.B., A.S. and O.S.; methodology, A.S.; validation, A.B., A.S. and O.S.; formal analysis, O.S.; investigation, A.B., A.S. and O.S.; writing—original draft preparation, O.S.; writing—review and editing, A.B.; visualization, A.S.; supervision, A.S.; project administration, O.S.; funding acquisition, O.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** The study was supported by the Russian Science Foundation gran<sup>t</sup> No. 23-27-00362, https://rscf.ru/en/project/23-27-00362/, (accessed on 14 March 2023).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.
