Insulative properties of crystalline rocks: On the problem of high-level radioactive waste disposal

In most countries (including Russia) where radioactive materials are used, it is suggest that high-level radioactive wastes (HLW) should be deposited in crystalline racks. We demonstrated that basic rocks (gabbro, anorthosite, basalt, and amphibolite) are most appropriate for this purpose. They are a viscous-rigid petrophysical type of material and are resistant to the destruction of a HLW repository by tectonic processes. Groundwater interacting with basic rocks attains reducing and slightly alkaline properties corresponding to the conditions of the lowest solubility of most radionuclides. The high reducing and neutralizing capacities of these rocks suppress deviations from these conditions caused by radiolysis. The basic rocks maintain low water permeability under the thermal effect of HLW. The interaction of groundwater and minerals in these rocks in the thermal held of a HLW repository have positive volumetric effects and are accompanied by the sealing of fractures and pores, a decrease in water permeability, and formation of secondary minerals with high sorption capacities. Thus, HLW disposal in low-silica rocks at depths below 500 m provides favorable conditions for the safe physical and geochemical isolation of radionuclides within a constrained rock volume.