| CFETR (China Fusion Engineering Test Reactor) is new generation of Tokomak device beyond EAST in China. Hot Cell, as major auxiliary facility, not only plays a pivotal role in supporting maintenance to meet the requirements of high duty time 0.3 to 0.5 but also supports installation and decommissioning. Hot cell is the place where deal with radioactive waste for the fusion device, it is different from general equipment maintenance factory, its internal processing are high levels of poisonous and harmful substances, so the technology for maintenance in hot cell is very complex. The cleaning and decontamination process is one of the several important works of maintenance and decommissioning project in hot cell for fusion reactor. Cleaning technology can reduce the radiation dose in the hot cell and restrictions on the radioactive effluent from hot cell to the nature environment in the maintenance process, so it plays a very important role. The effect of the cleaning process in the maintenance process in fusion hot cell is not only involving occupational exposure levels, nuclear facilities of the radioactive effluent control, remote operation of equipment and nuclear safety equipment life and reliability, radioactive pollutants diffusion such major problems of environmental protection, also directly affect experiments and security of fusion device.This study is aim to cleaning and decontamination process in the maintenance and decommissioning of the fusion reactor. Respectively, from the design principle, special process requirements, the cleaning method selection, teleoperation implementation scheme selection and design, cleaning process design and related equipment and components analysis and validation, disposal and recycling of cleaning waste and so on, carrying out the fusion device in-vessel components cleaning and decontamination teleoperation device key technology research, details are as follows:As we know, research on the maintenance for fusion reactor, at this stage is at very beginning, so the related research on hot cell is very less combined with the lack of relevant guidelines and evaluation criterion. We started our research from the whole maintenance process route and related design principles and specific requirements, puts forward CFETR overall maintenance plan at preparatory research phase:repair and decommission two different task of maintenance, and on this basis for IVC and remote handling equipment and related components detail maintenance processes are given. After systematic research and analysis on remote handling equipment R&D design principle including the ALARA, BAT, BEP, full life cycle management and some other key factor, such as tritium related operation principles, and detailed analysis of the hot cell inner maintenance interrelated key factors and principles and considering each principle with detail task, providing guidance for the selection and decision-making on the cleaning method which is most suitable used in the hot cell.In order to make the of cleaning and decontamination objects explicitly, we identified the composition and properties of dust in a large proportion of fusion devices aJl over the world, analyzes the potential hazards of radioactive particles in the maintenance process, and indicate the necessary and importance of cleaning the decontamination work in hot cell. According to the residual tritium, requirements of environmental protection and cleaning waste treatment, developing relevant treatment scheme and design guidelines, from analysis of several aspects and combines with deeply survey among a variety of radioactive contamination surface cleaning methods, selected dry ice blast cleaning method as the most suitable cleaning and decontamination preferred method in fusion hot cell, focus on its several existing problems, to find and adopt a series of relevant measures to solve related problems, at last, make plan for the overall cleaning and decontamination process route in hot cell for fusion device.According to the tritium protection and some other key issues related to the cleaning decontamination process and radioactive particles protective measures, double cladding structure was developed as the clean container, combining with the consideration of the cleaning implementation inside the cladding structure, the operation requirement restricts the execution mode should be more simple and direct, even be pipeline operation. In order to meet the requirements, a pneumatic conveying style dry ice cleaning wide mouth injector was developed and studied, combined with appropriate linear transport and relevant calculation and analysis for support structure, finally, proposing a cleaning decontamination process with triple air locks for gas atmosphere isolated from hot cell inner environment with the implementation of the remote handling cleaning operation process.Analyses of the pneumatic conveying wide mouth cleaning injector based on CFD method, which is used in the hot cell inner teleoperation decontamination cleaning operations. Numerical simulation on the interior of Continuous flow field was carrying out, get the pressure, velocity of flow field within the injector flow characteristics, on the basis of continuous flow field simulation of the injector, gas-solid two phase flow simulation with particles was also carrying out with injector interior flow field simulation and blanket wash effect simulation, the result of simulation proves feasibility of cleaning solution in hot cell for fusion reactor, through the traces of erosion under different erosion rate with the scope and degree of erosion verified the cleaning effect of pneumatic conveying wide mouth cleaning injector.Finally, For the treatment of cleaning waste which is the exhaust gas produced during the cleaning and decontamination process in hot cell, studying the composition of exhaust gas, making post-processing strategy with purify the purified carbon dioxide, adopting with mature gas industry technology, based on the oxidation absorption, cryogenic distillation, pressure swing adsorption (PSA) three different basic methods, in the principle to achieve the cleaning and radioactive waste minimization, research and develop the exhaust gas purification and cleaning agent recycling loop, completed the overall cleaning solution. Make the dry ice blasting cleaning method can truly be used in fusion device decontamination cleaning task. |
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