The technologies and strategies being developed to prevent or safely terminate plasma disruptions — events that could damage reactor components with forces of thousands of tonnes and heat loads of gigawatts.
ReviewedLast reviewed: 9 Aug 2026·Category: Glossary
Why Mitigation Is Essential
A major disruption in ITER would deposit up to 1 GJ of stored energy onto the first wall and divertor in milliseconds, generate runaway electron beams carrying up to 12 MA of current, and produce electromagnetic forces exceeding 10 MN on in-vessel components. Unmitigated disruptions could cause sufficient damage to require months of remote-handled repair.[1]
Three threats: (1) Thermal quench — 80% of the plasma’s thermal energy radiates or conducts to the walls in ~1 ms. (2) Current quench — the plasma current decays in 5–50 ms, inducing enormous eddy currents and electromagnetic forces. (3) Runaway electrons — the current quench’s electric field can accelerate electrons to multi-MeV energies, creating a relativistic beam that drills into the wall.
Mitigation Technologies
Massive gas injection (MGI): Injecting large quantities of noble gas (neon, argon) or deuterium to radiate the thermal energy uniformly before it reaches the walls. Shattered pellet injection (SPI): ITER’s baseline system fires frozen neon/deuterium pellets through a shatter tube, creating a spray of fragments that penetrate and radiate the plasma more uniformly than gas.[2]
Prevention
The preferred approach is to avoid disruptions entirely using real-time stability monitoring, exception handling, and controlled ramp-down when instability precursors are detected. Machine learning algorithms trained on large disruption databases are being developed for ITER disruption prediction.[3]
Sources
Lehnen, M. et al. "Disruptions in ITER and strategies for their control and mitigation." Journal of Nuclear Materials, 463, 39–48, 2015.
Combs, S.K. et al. "Shattered pellet injection as the primary disruption mitigation technique for ITER." IEEE Transactions on Plasma Science, 48, 1392, 2020.
de Vries, P.C. et al. "Survey of disruption causes at JET." Nuclear Fusion, 51, 053018, 2011.