TRANSPORT SIMULATIONS OF ITER WITH BROAD DENSITY PROFILES AND HIGH RADIATIVE FRACTION

Special versions of the 1.5-D BALDUR predictive transport code are used to explore the confinement in the ignited ITER EDA by self-consistent calculations. The code computes 2-D equilibria and solves 1-D transport equations in the bulk and scrape-off layer with empirical transport coefficients for the ohmic, L and ELMy H mode regimes. The emphasis is on scenarios with flat density profiles and high, fixed radiative power in the main chamber due to the seeded impurities argon and neon. It is shown that self-sustained steady state thermonuclear burn is achieved for 370 s and is compatible with the flat density profiles and strong radiative cooling. The necessary local energy and particle transport are presented. In the argon and neon scenarios, the required radiation corrected energy confinement times are 4.1 and 3.5 s, respectively, which are achievable according to the ITER ELMy H mode scaling. The advantage of neon originates from its smaller radiative loss within the separatrix of 37% of the total radiation in the main chamber, compared with 60% in the case of argon. A significant radiative loss from the confinement zone, mainly by bremsstrahlung, cannot be avoided. It raises the required energy confinement time and is the price to be paid for reduction of the divertor heat load by radiative cooling in the main chamber. In steady stare, a helium fraction of 5% is computed. The fractions of helium, argon and neon and the resulting fuel dilution are considerably lower than with peaked density profiles.