Effect of Two-Stage Shattered Pellet Injection on Tokamak Disruptions

Abstract

An effective disruption mitigation system in a tokamak reactor should limit the exposure of the wall to localized heat losses and to the impact of high current runaway electron beams, and avoid excessive forces on the structure. We evaluate with respect to these aspects a two-stage deuterium-neon shattered pellet injection in an ITER-like plasma, using simulations with the DREAM framework [M. Hoppe et al (2021) Comp. Phys. Commun. 268, 108098]. To minimize the obtained runaway currents an optimal range of injected deuterium quantities is found. This range is sensitive to the opacity of the plasma to Lyman radiation, which affects the ionization degree of deuterium, and thus avalanche runaway generation. The two-stage injection scheme, where dilution cooling is produced by deuterium before a radiative thermal quench caused by neon, reduces both the hot-tail seed and the localized transported heat load on the wall. However, during nuclear operation, additional runaway seed sources from the activated wall and tritium make it difficult to reach tolerably low runaway currents.

arXiv comment17 pages, 7 figures, to be submitted to Nuclear Fusion

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Cited by in corpus (9)

• Bayesian optimization of massive material injection for disruption mitigation in tokamaks
• Runaway dynamics in disruptions with current relaxation
• Fluid and kinetic studies of tokamak disruptions using Bayesian optimization
• The constraint of plasma power balance on runaway avoidance
• Runaway dynamics in reactor-scale spherical tokamak disruptions
• Non-linear MHD modelling of shattered pellet injection in ASDEX Upgrade
• Runaway electron generation in disruptions mitigated by deuterium and noble gas injection in SPARC
• An upper pressure limit for low-Z benign termination of runaway electron beams in TCV
• The impact of fusion-born alpha particles on runaway electron dynamics in ITER disruptions