Exhaust assessment of a European Volumetric Neutron Source (EU-VNS) using SOLPS-ITER

Abstract

EUROfusion considers a volumetric neutron source (EU-VNS) to generate a neutron wall load of about $0.5MW/m^2$ to qualify tritium breeding blankets early in support of EU-DEMO that mitigates the risk of a late testing for required nuclear technology. The envisaged small-scale $R=2.5m$ D-beam/T-target driven fusion device ($P_{fus}\approx 30MW$) must exhaust helium particles and dissipate sufficient energy from the large auxiliary power required ($P_{aux}\approx 50MW$) entering in large parts the edge. A SOLPS-ITER assessment indicates that with argon seeding a finite divertor operational window exists allowing to avoid core dilution by helium and to reduce the peak heat-flux density below $10MW/m^2$. It is shown that an extra constraint of $Z_{eff}<2-3$, required to sustain good core performance to produce the required amount of fusion neutrons, can also be met if the Greenwald-fraction $f_{GW}\approx 0.5$ is maintained with total T-throughputs at about half the ITER value. It is reasoned that for a EU-VNS design study the exhaust operational window can be enlarged by choosing other seeding species like Krypton, refining the balance between pellet- to gas-fuelling, and integrated core-edge modelling.