Scenarios for ITER steady-state and technology testing operation

Operational scenarios for the International Thermonuclear Experimental Reactor (ITER) steady-state and technology-testing phases are identified by tradeoffs among wall load, burn time, and divertor heat loads. Steady-state operation with Q ≥ 5 is limited to wall loads ≥0.5 MW/m² and injection powers ≥100 MW. Even at steady-state wall loads of 0.5 MW/m², the divertor heat loads are higher than predicted for the physics phase. For technology testing, hybrid operation (with simultaneous inductive and noninductive current drive) results in a wall load of 0.8 MW/m², with injection power of about 100 MW, a burn time of about 1200 s, and a divertor heat load similar to that of the physics phase. Significant uncertainty exists in present understanding of the divertor conditions. Should conditions prove to be more favorable than presently assumed, the operation windows would open considerably. For a factor of ≈3 reductions in predicted divertor loads, potential steady-state cases at wall loads of 0.8 MW/m², injection powers of about 130 MW, and Q near 7 are shown. With factors of ≈1.5-2.5 reduction in the predicted divertor loads, hybrid technology testing could be accomplished with wall loads of 0.8 MW/m², burn times of 1-3 h, and injection powers of 100-150 MW.