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Title: Runaway electron current after mitigated disruptions in ITER
Plain: ITER plans to shoot frozen pellets of deuterium and neon into a disrupting plasma to radiate its energy safely. Whether this also prevents a dangerous runaway electron beam, which grows by an avalanche of knock-on collisions, is uncertain.
Precise: In ITER disruptions mitigated by shattered pellet injection (SPI, fragmented D2 and Ne pellets), a small runaway seed from hot-tail generation, tritium beta decay and Compton scattering of gamma rays from the activated wall is amplified by avalanche multiplication. Compute the final runaway current versus injected D and Ne quantities, including losses through stochastic magnetic fields during the thermal quench and runaway-driven kinetic instabilities, and determine whether any injection scheme keeps the runaway current below the wall-tolerable level.
Settled by: Validated 3D MHD plus kinetic runaway modeling of ITER SPI scenarios, confirmed by ITER commissioning disruptions.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: 2026 modeling with improved physics (arXiv:2602.22177) finds most D-T H-mode SPI scenarios exceed tolerable runaway currents but identifies one theoretically viable D-T scheme; no experiment reaches ITER-scale avalanche gain.
Posed since: (empty)