The wooden box containing ITER’s first Inner-Vertical Target (IVT) prototype left from the workshop of Ansaldo Nucleare (Genoa, Italy) and travelled at least 2800 km to reach the doorstep of the Efremov Institute (Saint Petersburg, Russia) in order to go through its first tests. Don’t feel any pity for this piece of equipment leaving the moderate European climate for a chillier one. It is meant to be resistant and eventually in the ITER machine it will be one of the components that will be exposed to the super-hot temperatures of the plasma. This is why engineers call it a “plasma facing component”.
The IVT prototype, weighing 0.5 t and measuring approximately 1.5 m, is covered by 1104 tungsten blocks, which to the eyes of a layman they resemble to thick “tiles” made of steel. Its shiny surface is wrapped carefully because it is brittle. In spite of the fact that it can sustain high heat fluxes, its surface can be easily cracked. Each of the eight rows of the tungsten blocks is piled onto a copper alloy pipe in which pressurised water will flow to cool down the component. At the Efremov Institute, the host of the ITER Divertor Test Facility, there is an upbeat feeling of anticipation because the staff will get to test this full scale component for the first time-ever. “It’s an important milestone attracting the attention of F4E’s stakeholders because it will pave the way to manufacturing the real IVT” explains Pierre Gavila, managing this contract on behalf of F4E.
As the equipment gets unwrapped, a series of inspections is carried out to cross-check that it hasn’t been damaged in any way. Then the prototype is assembled on equipment which will be used to carry out the tests. It is positioned on a special kind of “table” that can be easily manipulated so as to proceed with the water connections and final preparations. The “table” is then rolled inside a vacuum chamber-where in tests will be carried out.
The surface of the prototype will be “divided” into three test areas which will experience distinct temperatures. Each area will be tested at a certain heat flux and for a given number of cycles. The curved parts will receive 5000 cycles at 5MWm2 and the two straight parts 5000 cycles at 10 MW/m2, followed by 300 cycles at 20 MW/m2 respectively. Almost like the “test of fire”, these rigorous trials using high-power electron irradiation, will help us discover how much this equipment can take. The tests are expected to run until early 2019. Then, the prototype of the plasma facing unit will be dismounted, packed and returned to Ansaldo Nucleare. Once received, the IVT prototype manufacturing will be completed, and testing will be concluded later in 2019.
“This is the first time an In-Vessel full-scale prototype is tested at such length, produced in line with the ITER requirements” elaborates Gavila. “The tests will help us to validate the materials, the machining and the route of manufacturing in order to draw lessons for the production of the real component that will be used in ITER.”