Material activation observation on the Tore Supra Tokamak

Radioactive isotopes are produced in Tokamaks that use deuterium plasmas. Although only produced in small quantities, their study is of major interest, first for the safe operation of these devices, and second to forecast what can be expected in larger future machines. Analysis performed on the Tore Supra Tokamak has shown that three main processes are involved in the production of these radioactive elements: the capture of the neutrons produced by the plasma, photo-nuclear reactions caused by runaway electrons and proton–boron fusion reaction, which produces the radio-nuclide Be7. On intermediate size machines, such as Tore Supra, the observed activities and dose rates are too low to justify any remote handling operation. A threshold can be defined in the neutron production for the limit between hands-on and remote maintenance, which is found around 1020 neutrons per year, or 100 MJ of D–D fusion energy.