Overview of bore tools robot for nuclear fusion reactor maintenance

摘要

Because of the radiation levels preventing direct, hands-on access to the machine components, maintenance work on ITER fusion experimental reactor will require the use of Remote Handling (RH) techniques. In particular, the replacement of components such as divertor and blanket modules will require the use of remote cutting, welding and Non Destructive Testing (NDT) of water cooling pipes. During the engineering design phase of ITER, a significant effort was done to develop Bore Tools Systems (BTS) for the remote maintenance. The results of previous work is here presented and new tooling solutions, in particular for use on the divertor maintenance, are discussed. The ITER First Wall (FW) assembly consists of 54 divertor cassettes located at the bottom of the Vacuum Vessel (VV) and 500 blanket modules to cover the entire Tokamak F.W.. Each of them is mechanically locked to the VV and connected to two water cooling pipes. Due to the need to replace the eroded plasma facing components (PFC's), theses components require to be periodically removed and re-installed from/into the VV. This operation requires, among others, the cutting, re-welding and inspection of hundreds of cooling pipes. The ITER machine geometry imposes severe geometrical constraints on the components which in turn affect the pipe tooling design and maintenance access. Therefore, a BTS technology, being more compact, has been selected. Commercially available tools have been considered but found not suitable for this application. A new set of pipe tools has been designed, developed and finally validated through a comprehensive R&D program. The program included parametric studies to assess the cutting, welding and NDT processes, with also tools deployment test inside 4" diameter pipes (316L) with 400 mm bend radius. This was achieved by developing a new, modular type, tool deployable system. This system is able to negotiate the various pipe bends and to overcome the friction forces generated during the tool system progress inside the pipe. The tests included the demonstration of pipe alignment prior to welding, which requires to generated high forces in-pipe, and also tools rescue in case of failure. While additional tests may be required, the initial development program indicates that the proposed bore tool system is a viable solution for the maintenance of ITER.