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 des truction of a HLW repository by tectonic processes. Groundwater interacting with basic rocks attains reducing and slightly alkaline properties corresp onding to the conditions of the lowest solubility of most radionuclides. Th e high reducing and neutralizing capacities of these rocks suppress deviati ons from these conditions caused by radiolysis. The basic rocks maintain lo w water permeability under the thermal effect of HLW. The interaction of gr oundwater and minerals in these rocks in the thermal held of a HLW reposito ry have positive volumetric effects and are accompanied by the sealing of f ractures and pores, a decrease in water permeability, and formation of seco ndary minerals with high sorption capacities. Thus, HLW disposal in low-sil ica rocks at depths below 500 m provides favorable conditions for the safe physical and geochemical isolation of radionuclides within a constrained ro ck volume.