MK Reactor Decommissioning in NRC 'Kurchatov Institute': Results of Preparatory Work Phase - 13127

In 2008, in the framework of the Federal Target Program 'Nuclear and Radiation Safety Assurance in Russia in 2008 and for the period till 2015', NRC 'Kurchatov Institute' has launched the decommissioning of its research reactors MR and RTF. Kurchatov Institute has been developed and commissioned MR research reactor in 1962-1963 in order to replace its previous uranium-graphite reactor RTF. During this replacement RTF equipment has been dismantled, its nuclear fuel removed, and its in-core structures embedded in concrete inside the pit situated in the central hall of the MR - a pool-type reactor equipped with nine experimental loop-type channels with different coolants. Reactor structural elements were installed into a 9-meter-deep water pool. In 1992 this reactor has been stopped and for 18 years was in the state of ultimate shutdown. In 2009 the decommissioning project was developed for MR and RTF and approved by the Expert Authority of the Russian Federation (Gosexpertiza). This project identified the following ultimate state of the reactor facility: - complete dismantling of reactor equipment and systems; - decontamination of reactor premises and site in accordance with the established sanitary and hygienic standards. This MR/RTF decommissioning project consisted of the preparatory phase and the basic phase. The preparatory phase (2008-2010) included: loop-type channels' dismantling in the storage pool; experimental fuel assemblies' removal from spent fuel repositories in the central hall; spent fuel assembly removal from the liquid-metal-cooled loop-type channel of the reactor core and its placement into the SNF repository; and reconstruction of engineering support systems to the extent necessary for reactor decommissioning. The basic phase includes the following works: - 2011-2012: dismantling of equipment/pipelines of cooling circuits and loop-type channels and auxiliary reactor equipment; - 2013-2014: dismantling of equipment in underground reactor premises and of both MR and RTF in-vessel devices; - 2015: final radiation survey of reactor premises, loop-type channels and site; decontamination of reactor premises; rehabilitation of the reactor site; and issuance of the regulatory authorities' de-registration statement. By the moment all works foreseen for the preparatory phase are already completed; in 2011 the decommissioning license for the two reactors was received and direct MR decommissioning activities started. In 2011 MR primary pipelines and loop-type facilities situated in the underground reactor hall were dismantled. Works were also launched to dismantle the loop-type channels' equipment in underground reactor premises; reactor buildings were reconstructed to allow removal of dismantled equipment; and the MR/RTF decommissioning sequence was identified. Results of activities performed in 2011: - equipment from two underground rooms (no. 66 and 72) - as well as from water and gas loop corridors - was dismantled; - loop-type channel equipment from underground reactor hall premises was dismantled; - 50 loop-type channels were chopped, with 14 channels packaged and removed to the SNF repository. Technologies involving the application of remote-control tools during radiation-hazardous dismantling operations have enabled pre-decommissioning works on MR and RFT research reactors to be performed with personnel exposure meeting the effective safety standards. As a result of works completed in 2008-2011, a radiation survey was performed on reactor equipment and premises. Dismantling, fragmenting and removal of the liquid-metal-cooled loop-type facility containing a fuel assembly were also completed. Auxiliary systems were prepared to support reactor decommissioning activities. High-level waste storage space to be subsequently filled with waste to be produced in the main course of the MR decommissioning project was cleared in the Kurchatov Institute's central repository. MR reactor hall under-floor pipelines were dismantled; the total of 93 channels with cumulative activity of 2.6x10¹³ Bq (⁶⁰Co) and 1.5x10¹³ Bq (¹³⁷Cs) were removed, chopped and packaged; some part of this waste was placed in the vacated cells in HLW repository. Use of remote-control mechanisms allowed the radiation exposure of personnel to be reduced. In 2011, average individual dose for personnel was 1.9 mSv/y, and the collective dose was estimated as 0.0065 man Sv/y. These pre-decommissioning works have made it possible, in 2012, to start dismantling the equipment in the MR loop facility premises, removing loop pipelines from the basement rooms, and organizing technological openings in-between. The experience of equipment dismantling with the use of remote-control mechanisms, as well as remote methods and means of radiation survey and monitoring, will be used in the future reactor core dismantlement works.