Insufficient helium exhaust can seriously degrade the performance of any fusion reactor and has recently been identified as a potentially significant issue for the International Thermonuclear Experimental Reactor (ITER). The effects of variations of the ratios DHe/χi, DHe/DD and vHe/DHe and of the sawtooth period on helium exhaust in ITER have been studied with BALDUR code transport simulations. Recent measurements of DHe/χi in TFTR, of DHe/DD in TEXTOR and of vHe/DHe in TFTR, TEXTOR and JT-60 are found to be compatible with the requirements of sustained ignition and helium exhaust for ITER. Ignition is found to be critically sensitive to the ratio vHe/DHe, particularly at the plasma edge, and to a reduced sawtooth period. These critical dependences are moderated for reduced helium recycling at the separatrix and for hollow particle diffusivity profiles.
Transport simulations of the ignited ITER with high helium fraction