Assembly process of the ITER neutral beam injectors

Abstract

The ITER neutral beam (NB) injectors are used for heating and diagnostics operations. There are 4 injectors in total, 3 heating neutral beam injectors (HNBs) and one diagnostic neutral beam injector (DNB). Two HNBs and the DNB will start injection into ITER during the hydrogen/helium phase of ITER operations. A third HNB is considered as an upgrade to the ITER heating systems, and the impact of the later installation and use of that injector have to be taken into account when considering the installation and assembly of the whole NB system. It is assumed that if a third HNB is to be installed, it will be installed before the nuclear phase of the ITER project.The total weight of one injector is around 1200t and it is composed of 18 main components and 36 sets of shielding plates. The overall dimensions are length 20m, height 10m and width 5m.Assembly of the first two HNBs and the DNB will start before the first plasma is produced in ITER, but as the time required to assemble one injector is estimated at around 1.5 year, the assembly will be divided into 2 steps, one prior to first plasma, and the second during the machine second assembly phase. To comply with this challenging schedule the assembly sequence has been defined to allow assembly of three first injectors in parallel. Due to the similar design between the DNB and HNBs it has been decided to use the same tools, which will be designed to accommodate the differences between the two sets of components. This reduces the global cost of the assembly and the overall assembly time for the injector system.The alignment and positioning of the injectors is a major consideration for the injector assembly as the alignment of the beamline components and the beam source are critical if good injector performance is to be achieved. The theoretical axes of the beams are defined relative to the duct liners which are installed in the NB ports. The concept adopted to achieve the required alignment accuracy is to use the main rail of the overhead crane associated with offset tooling when necessary. The overhead crane is used for the assembly of the components, and the final positioning of the beamline components and the beam source will be adjusted with respect to laser targets referring to the optimum beam axis and source position.This paper describes the installation tasks and the alignment and positioning solutions and the complexity of operations within the NB cell. Particular constraints on the HNB installation sequence due to the planned testing of the 1MV high voltage supply are also described.