The role of underground research laboratories (hereinafter URL) is recognized globally and involves the following points: URL enables research and demonstration aimed at evaluating the feasibility of technological processes under actual spatial scales and geological setup. In recent years, quite a lot of articles and reviews was published [1][2][3][4][5], concerning the issues associated with URLs established to demonstrate the safety of radioactive waste deep geological disposal. It should be noted that 25 URLs were developed globally for various purposes. Most similar to the Russian one by their purpose are those being site-specific (located at potential disposal sites) and excavated in crystalline bedrock (granite and gneiss), namely: operating URL ONKALO (Finland) and the one planned for construction in 2020 in China (Beishan Province). Among all the publications there are several articles [6][7][8][9][10][11][12][13][14] focused on particular studies planned to be carried out in the Russian URL being under construction at the site of Nizhnekanskiy massif in the vicinity of Zheleznogorsk city (Krasnoyarsk region). This paper presents the designs of the Russian URL being for the first time ever discussed in a holistic and dynamic manner starting with the construction stage and up to the closure of the disposal facility.

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Rock mass is considered as a natural barrier impeding the release of radioactive waste into the environment, being part of a multi-barrier system designed to ensure the safety of deep disposal facilities for radioactive waste (DDF RW). A number of regulatory documents [1] and recommendations [2, 3] states the importance of the geological medium, namely, its characteristics for the long-term safety of RW disposal. Current stage of URL development project is specifically focused on providing the opportunities for geological research covering target RW disposal horizons solely via borehole methods before the entire complex of underground excavations is formed. Due to long-term operation of wells and their initial design features, the state of some of these wells has appeared to be unsatisfactory requiring reconstruction. In addition, in accordance with certain legislative requirements, all wells shall be abandoned after relevant operations have been completed. The article discusses the reconstruction and abandonment of wells drilled at the Yeniseiskiy site. It demonstrates the feasibility of proposed designs providing the opportunities for further expansion of studies to investigate the state of rocks under natural conditions and to arrange for monitoring. The paper provides an evaluation and comparative analysis of plugging materials proposed to be applied under well abandonment operations.

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