Power Handling in ITER: Divertor and Blanket Design and R and D

Full text: One of the most technically challenging components of the ITER machine are those directly facing the thermonuclear plasma. The plasma-facing components (PFCs), include the Divertor and the Blanket, and consist of a plasma facing material (the 'armour') mounted onto a heat sink and supported by a structural/shielding material. The development of suitable technologies for the power handling of the stationary thermal loads has required an unprecedented R and D effort by all the concerned Domestic Agencies over the last two decades. The main function of the divertor is exhausting part of the plasma thermal power (including the alpha particle power), as well as minimizing the helium and impurity content in the plasma. The ITER divertor consists of 54 cassette assemblies which are inserted radially through three lower level ports and moved toroidally before being locked into position. Each cassette assembly includes one Cassette Body and three PFCs, namely the inner and outer Vertical Targets, and the Dome. The inner and outer targets are the PFCs, which in their lower parts directly interact with the SOL and in their upper parts act as baffles for the neutrals. The main functions of the blanket system are: (1) to exhaust part of the plasma power, (2) to contribute in providing neutron shielding to superconducting coils and (3) to provide limiting surfaces that define the plasma boundary during startup and shutdown. The system comprises two different sub-systems that cover the ITER inner vessel wall. The wall-mounted blanket modules covering 620 m2 and the port-mounted blanket modules covering 40 m2. The wall mounted blanket modules (BMs) consist of two major components, a plasma-facing First Wall panel, with a beryllium armour, supported by a Shield Block. The required remote handling, the extremely high electromagnetic and thermal loads, the number of physical interfaces with the rest of the machine and with the diagnostics as well as the direct interaction with the plasma, make the identification of a viable design solution of the ITER PFCs one of the most challenging design and R and D efforts of the entire machine. This paper summarizes the status of the Divertor and the Blanket, the related R and D effort, and gives an outline of the construction schedule. (author)