The article overviews the findings of individual studies under the Program of Calculation and Experimental Research Seeking to Demonstrate and Assess the Long-term Safety of Deep Disposal Facilities for Liquid Radioactive Waste Aiming to Implement the Recommendations of the IAEA Peer Review of the Deep Well Injection Practice for Liquid Radioactive Waste in the Russian Federation. To demonstrate the long-term safety of the Zheleznogorsk, Seversk and Dimitrovgrad deep disposal facilities for liquid radioactive waste (hereinafter referred to as the DDF LRW), data on the geological and hydrogeological conditions in the regions and at the DDF LRW sites were collected and systematized; the processes occurring in DDF LRW near and far zones, including those involved in radioactive waste (RW) component transport, were studied; evolution scenarios for the RW disposal system were developed, including a forecast describing potential climate changes in the DDF LRW areas covering a period of up to 100,000 years; conceptual and mathematical DDF LRW models were developed; computer software was used in predictive calculations focused on the migration of liquid RW components in the operational DDF LRW horizons with the potential radiation impact on the population been assessed. The study also involved some computational and experimental research focused on the evolution of backfill materials to develop the designs of some additional engineered safety barriers to be installed during DDF LRW DGR well abandonment; the paper also presents the approaches to the development of the DDF LRW closure concept.

The paper presents experimentally evaluated parameters of 14C and 36Cl leaching from irradiated RBMK-1000 graphite in aqueous media of various compositions, including distilled water and those stimulating the groundwater. To predict further radionuclide migration and to demonstrate the disposal safety, an array of initial data was formed presenting the characteristics of RBMK-1000 graphite stacks. The paper proposes an optimal approach describing numerically the function of the leaching dynamics. It also compares the calculated dynamics of 14C and 36Cl leaching from GR‑220 (PUGR) and GR-280 (RBMK-1000) graphite.