Effects of the Neutral Beam shine through on the first wall of the ITER Thermo-nuclear Fusion Reactor

During the plasma start-up operation of the ITER Thermonuclear Fusion Reactor, the plasma receives additional heating from the Neutral Beam (NB) Injectors. These devices produce intense beams of high energy neutrals (mainly Deuterium). These beams once in the plasma chamber get ionised and transfer part of their kinetic energy to the plasma by interacting with its particles, increasing its temperature. The NB can be shut off when the plasma reaches ignition. However a plasma disruption could occur while the NB is operating. In this case, due to the sudden loss of plasma density, the NB will be entirely dumped onto the first wall opposite to the NB ports, which will be locally subjected to extremely high heat fluxes, until the protection system will shut off the NB. This event is called neutral beam shine through (NBST). The transient thermal response of the first wall subjected to the NBST thermal load has been analysed and is presented in this paper.