Study of radiation limits in fusion reactor scenarios

Radiative mantle scenarios of the ignited ITER FDR (Final Design Report) with argon and neon seeding are explored by self-consistent simulations with a special version of the 1.5-D BALDUR predictive transport code. The calculations apply empirical transport coefficients and are carried out both in the bulk and in the SOL. Operation relevant upper limits to the radiative power losses from the main chamber, from closed flux surfaces and from the SOL are found. Both simulations and an analytic study of power balances show that these limits are set by the radiation profile and by the cross-field heat conduction in the SOL. For given heating power, the conductive heat flux across the separatrix and the energy flow to the divertor are also restricted. With high edge density, the required thermal energy confinement times at the radiation limits are found to be 4.4 s in the argon and 4.0 s in the neon scenario. The assumption of flat density profiles and no inward pinch in the whole plasma is supported by simulations using a new scaling relation for the anomalous inward drift. The dependence of the radiation limits on the separatrix density is investigated. Formulas for relevant power limits are presented.