Fusion's wet blanket

Seven international partners are building the world's biggest fusion reactor, ITER, at Cadarache in Southern France. The biggest challenges in the development of nuclear fusion are not in the plasma, but in the energy-absorbing lithium blanket that surrounds it. The fusion community is developing a facility, the International Fusion Materials Irradiation Facility (IFMIF), to test small samples of the promising materials. The test samples will be irradiated in a beam of neutrons for several years to evaluate the changes in structural properties. The blanket is a complex system to extract heat and tritium that operates at high temperature, in a harsh neutron environment. Tritium is extracted from the blanket regularly and used to fuel the plasma to keep the radioactive inventory low. A pragmatic approach to fusion would be to build component test facilities in parallel with ITER.