A Study of Pipe Jointing Technology with Reference to ITER Requirements

The successful performance of remote automated welding of pipe joints depends on the precise control of many parameters. In practice, small variations in geometry, metallurgy and weld power prevent the creation of the optimum joint every time. To minimise the risks of producing welded joints of unacceptable quality, the approach at JET was to simplify the joint design. This meant specifying autogenous, single pass welds for pipe joints wherever possible. The requirements of ITER are such that this simplification of the weld process cannot necessarily be achieved. The pipe sizes and thicknesses will probably demand the use of multi-pass welds with the addition of filler metal. This paper looks back at the experience of the JET project in endeavouring to achieve this type of joint and highlights the difficulties that ITER will need to overcome. Similarly for the pipe cutting process, the JET team was able to develop tooling that was simple and reliable due largely to the thin pipe wall thickness used on the project. The ITER requirement for all processes to be fully remote will demand the development of more sophisticated welding and cutting tools with particular capabilities for recovery from failure. In response to the difficulties foreseen with applying welding and cutting principles to the pipe jointing challenges at ITER, research is currently underway with the aim of identifying an approach that is more amenable to Remote Handling (RH). This paper documents a proposal for a novel UHV pipe jointing system based on an in situ reversible brazing technique.