Sample-taking to Characterize Organic Solvent Contained in a Tank in a Shielded Room Involving 3D Modeling of the Room and the Equipment Present, Followed by the Development of Special Tools

摘要

Licensed Nuclear Facility 57 consists of three buildings: Building 18 (hot lab), Building 91 (chemicalrnengineering hall) and Building 54 (equipment store). This facility has been under decommissioning since 1st July 1995.rnBuilding 18, formerly a radiochemistry laboratory, used for chemical research relating to the reprocessing of spent fuel andrnother issues as well as to the production of transuranic radionuclides, is undergoing clean-up prior to dismantling. In arnlaboratory of this type, the clean-up operations include reduction of radioactivity levels and chemical hazards associatedrn-with the equipment. This process notably includes draining and treatment of contents of process and effluent tanks.rnThe research and production work was performed in a facility comprising a shielded production line and a shielded roomrncontaining two effluent tanks and three process tanks, the production line and the tank room being linked by a plant duct.rnIn 1974, use of the tank in the room was abandoned as a result of a breach in a high-level effluent tank After management ofrnthe incident (recovery of the liquid contained in the catchment basement), process Tanks A and C containing aqueous liquorsrnwere drained in the early eighties by pumping through the production line. The contents of Tank B could not, at the time, berntransferred to the production line workstations via the existing systems.rnAs the drawings of the room were not reliable, an initial video inspection was made in 1995 via bore holes made in thernceiling. In 1997, it was planned to drain the contents of the tank using a tank level measuring pipe. This proved to bernimpracticable. It was then decided to take, from outside, a sample of the contents of the tank from the former control roomrnlocated above the tank room. An initial set of equipment was installed in the room with the collaboration of the DDCO/SDSPrnteams on the basis of the results of the 1995 video inspection and the drawings available. A 3D model was then created andrncorrected by video inspection and the use of environment reconstruction software developed by DTSI/SRSI. The 3D modelrnobtained enabled 3D simulation of the special tools and protocols necessary for the operation, including core drilling forrnaccess (size and position). The construction of a full-scale model, on the DDCO/SDSP test platform, enabled a protocol to bernestablished and the operators to be trained.rnOnce the necessary authorizations were obtained for core drilling the ceiling above the tank as required for sample-taking, the operations carried out in June 2004, samples were then taken which made it possible to establish the radiological,rnphysical and chemical properties of the solvent and to confirm the feasibility of decontamination. At the same time, studies were carried out in liaison with DRCP/SCPS of the possible ways of dissolving any solid deposits.