Handling of low-level wastes at the Siberian Chemical Works

Abstract

Safety codes require that open surface disposal sites for liquid low-level wastes at radiochemical works be closed down. At the Siberian Chemical Works, the first operation was to stop the flow of wastes into the pulp repository. The presence of burial sites predetermined the choice of precisely this method as an alternative for dumping wastes into open disposal sites. The results of a study of the physicochemical characteristics of the wastes flowing into the pulp repository PKh-1,2 from four plants at the Works made it possible to develop a unified scheme for preparing them for disposal -wastes are put into a deep repository and maximum use is made of the individual properties of reprocessed wastes, which decreases the consumption of additional reagents substantially, i.e., it decreases the cost of the preparation process. The scheme developed has successfully passed commercial prototype tests and is now in the design stage.The production operations at the Siberian Chemical Works produce liquid radioactive wastes with different salt composition and content of radionuclides and suspensions. At the first stage, surface disposal sites, which keep radionuclides out of the open hydrographic network, were built to salvage liquid wastes. Subsequently, the favorable hydrogeological conditions at the plant site made it possible to implement on a commercial scale the underground method for disposing of wastes in sandy collector formations deep underground and to avoid building additional surface repositories [1].The first geological exploration work performed in our country to validate the safety of deep disposal of liquid wastes was begun in the mid-1950s at the Siberian Chemical Works by the Novosibirsk Geological Office. Subsequently, the wastes were transferred to the enterprise Gidrospetsgeologiya. The results of the investigations made it possible in 1963 to begin operation of an experimental section of the site and in 1967 to switch to a commercial variant of deep disposal of liquid low-level wastes. The purpose of the site is to localize and store (hold) wastes in deep collector formations in order to allow the concentration of radionuclides to drop below the intervention level by decaying [2].The site lies in the southeastern part of the Ob' artesian basin. A section of the region, from bottom to top, shows the water-bearing system of the Paleozoic basement, the bottom water-bearing system of sedimentary sandy-clayey Mesozoic rock (bottom and top Cretaceous), and the upper water-bearing system of sandy-clayey rock of the Cenozoic era (Paleogene, Neogene, and Quaternary). The bottom water-bearing system of Mesozoic rocks includes the water bearing levels I, II, and III and the confining beds A, B, C, and D (arbitrary enumeration) separating them. The upper water-bearing system of