A simulation study of large power handling in the divertor for a Demo reactor

Abstract

Power exhaust for a 3 GW class fusion reactor with an ITER-sized plasma was investigated by enhancing the radiation loss from seeding impurity. The impurity transport and plasma detachment were simulated under the Demo divertor condition using an integrated divertor code SONIC, in which the impurity Monte-Carlo code, IMPMC, can handle most kinetic effects on the impurity ions in the original formula. The simulation results of impurity species from low Z (neon) to high Z (krypton) and divertor length with a plasma exhausted power of 500 MW and radiation loss of 460 MW, and a fixed core–edge boundary of 7 × 1019 m−3 were investigated at the first stage for the Demo divertor operation scenario and the geometry design. Results for the different seeding impurities showed that the total heat load, including the plasma transport and radiation , was reduced from 15–16 MW m−2 (Ne and Ar) to 11 MW m−2 for the higher Z (Kr), and extended over a wide area accompanied by increasing impurity recycling. The geometry effect of the long-leg divertor showed that full detachment was obtained, and the peak qtarget value was decreased to 12 MW m−2, where neutral heat load became comparable to and due to smaller flux expansion. Fuel dilution was reduced but was still at a high level. These results showed that a divertor design with a long leg with higher Z seeding such as Ar and Kr is not fulfilled, but will be appropriate to obtain the divertor scenario for the Demo divertor. Finally, influences of χ and D⊥ enhancement were seen significantly in the divertor, i.e. the radiation and density profiles became wider, leading to full detachment. Both qtarget near the separatrix and Te at the outer flux surfaces were decreased to a level for the conventional technology design. On the other hand, the problem of fuel dilution became worse. Extrapolation of the plasma transport coefficients to ITER and Demo, where density and temperature will be higher than ITER and edge-localized modes are mitigated, is a key issue for the divertor design.

Divertor Study on DEMO Reactor

“…The power handling in the SlimCS divertor plasma using the Ar seeding have been investigated by using the SONIC suite [10][11][12][13]. The numerical setup for the SONIC simulation is as follows: at the core interface boundary (r/a ∼ 0.95), the deuterium ion density n cib D is fixed to n cib D = 7 × 10 19 m −3 and the total exhausted power P cib = P ext is set to be 500 MW, which corresponds to P fus = 3 GW.…”

“…For the fusion power of P fus ∼ 3 GW, P ext ∼ 500 MW is expected. A power handling scenario has been investigated by using a suite of integrated divertor codes SONIC [8,9], in order to produce the detachment (the electron temperature T e less than a few eV for suppression of the target erosion) at the divertor target [10][11][12][13]. As will be discussed in section 3, SONIC simulation for the SlimCS divertor plasma with the large Ar impurity seeding shows the divertor power load is still higher than 10 MW/m 2 , although 92 % of P ext is radiated by the Ar impurity.…”

Progress of Divertor Study on DEMO Design

“…The power handling scenario for a 3 GW class fusion reaction with an ITER-sized plasma (∼ 5.5 m), SlimCS [1,2], has been investigated [3][4][5]. The primary technique for reduction of the divertor heat load to such a desirable level is enhancement of the radiation loss by impurity gas seeding.…”

Development of the Backflow Model for Simplified Impurity Exhaust in Monte‐Carlo Calculation

“…A suite of integrated divertor codes SONIC [4,5] has been developed for analysis of experimental data [4,6] and divertor design of future machines, such as JT-60SA [7,8], DEMO reactor [9][10][11][12] etc. The SONIC suite consists of the plasma fluid code SOLDOR, the neutral Monte-Carlo (MC) code NEUT2D and the impurity MC code IMPMC.…”

“…Recently, predictive SONIC simulations of the divertor power handling by noble gas impurity seeding for JT-60SA and DEMO reactor have been carried out [8,11,12]. In such simulations, long exhaust processes for the noble gas impurity became problem.…”