Decommissioning of uranium-graphite nuclear reactors and radioactive waste handling

In accordance with the agreements between the Russian and US Governments on completion of weapons plutonium production, ten powerful industrial reactors were unloaded and decommissioned in the Russian Federation. Three such reactors, I1, E2 and ADE3, were decommissioned after 30 years of operation. The decommissioning concept started in the middle 1990s, comprising the dismantling of low-activity structures, sealing of all reactor outlets, and filling of all reactor spaces with special compounds of concrete and betonite. All these arrangements ensured multi-level protection with a number of safety barriers between the reactor and the environment. As a result, the suggested decontamination and decommissioning concept allowed qualification of the structure under the IAEA's Stage 2 and ensured its safety for over 300 years.The presence of radiation and restricted access to the reactor components led to the development of remote controlled equipment and for electrical contact or mechanical cutting methods, for welding and remote sampling of radioactive metal and other items. The paper also discusses the cost of the work that has been performed, personnel exposures, the quantity of filling materials consumed for the support structures, as well as the handling of radioactive wastes (i.e. reactor products).The ways they were unloaded, their selection, how they were contained, their transport and termination are described. Particular attention is paid to the use of special compounds with betonite ingredients as a protection against radiation, which ensures multi-layered protection for radioactive waste on the basis of the 'matrix-isolation-coat' principle. This allows the radioactive waste to be stored at a decommissioning site. (author)