Safety substantiation for underground isolation of spent nuclear fuel or spent nuclear materials as a basis to develop reliable technological solutions

Major issues of the technique for mining and ecological safety substantiation of multi-barrier systems for long-term underground isolation of spent nuclear materials and solidified wastes containing long-lived radionuclides have been presented. The experience with the use of this technique for assessment of ecological safety for the long-term storage of plutonium-containing intermediate level wastes in underground facilities existing in the crystalline rock mass has been considered. The probabilistic evaluations of events of the emergency sequences of abnormal situations are based on the results of 40-year in-situ investigations in the rock mass. Feasibility of optimization has been shown for technological design solutions on storage facilities by the ''risk-costs'' principle. (authors)