Materials testing for Iter components

12 October 2016

NRG at Petten in the Netherlands is preparing to use its high-flux reactor (HFR) to test the operation, integrity and quality of the “first wall” that will shield the nuclear fusion process at the €15bn ($17bn) International Thermonuclear Experimental Reactor (Iter) under construction at Cadarache, France. Iter is intended to demonstrate the scientific and technological feasibility of fusion power. The project is being undertaken by seven members – Europe, the US, Russia, Japan, China, South Korea and India.

The first (innermost) wall comprises beryllium tiles welded onto the subsurface of a copper-chrome-zircon alloy enclosed in a stainless steel construction. Mock-ups of the first wall will be placed in the reactor core at Petten and exposed to intense neutron radiation. “This enables us to simulate the radiation environment and temperatures in Iter,” said Sander de Groot of NRG. The fusion process at Iter will occurs in plasma at a temperature of 150m kelvin.

Because no material can withstand this kind of temperature, the plasma is held in place by a magnetic field. De Groot said the HFR can simulate potential radiation damage during Iter’s lifespan and determine how long components can withstand the neutron radiation. After irradiation in the HFR, the irradiated mock-ups will be transported to the Jülich research centre in Germany, where they will be exposed to an extremely high heat flux and intense variable thermal radiation. This will demonstrate whether the irradiated material offers sufficient resistance to the extreme heat load in the Iter system.

Meanwhile, the first of three Chinese-supplied electrical transformers has been installed at the Iter project. The 14 metre long, 280t transformer forms part of the electrical network that will provide power to Iter's "pulsed" systems, such as magnet power supplies and plasma heating systems. It was delivered to the site in June. It took two days to move the giant component into position from its storage site. First, it was delivered by hydraulic trailer to the installation site, where it was lowered onto railway-type wheels. It was then hauled into its final position along pre-built tracks. Before it begins operation, the transformer will be filled with insulating oil and fitted with other equipment including the bushings needed to connect it to the switchyard, bringing its total weight to 460t. Two other transformers are due to arrive from China in early 2017 to be connected to the switchyard by the middle of the year.

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