Study of radiation limits in fusion reactor scenarios

Abstract

Radiative mantle scenarios of the ignited ITER FDR (Final Design Report)with argon and neon seeding are explored by self-consistentsimulations with a special version of the 1.5-D BALDUR predictivetransport code. The calculations apply empirical transport coefficientsand are carried out both in the bulk and in the SOL.Operation relevant upper limits to the radiative power losses fromthe main chamber, from closed flux surfaces and from the SOLare found. Both simulations and an analytic study of power balancesshow that these limits are set by the radiation profile and by thecross-field heat conduction in the SOL. For given heatingpower, the conductive heat flux across the separatrix and the energyflow to the divertor are also restricted. With high edge density,the required thermal energy confinement times at the radiation limitsare 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 thewhole plasma is supported by simulations using a new scaling relationfor the anomalous inward drift. The dependence of the radiation limitson the separatrix density is investigated. Formulas for relevant powerlimits are presented.