Modifications to the JET Shattered Pellet Injector to Optimize Disruption Mitigation Experiments for Supporting ITER’s DMS Design

Journal Article · Wed Feb 21 00:00:00 EST 2024 · IEEE Transactions on Plasma Science

DOI:https://doi.org/10.1109/tps.2023.3340910· OSTI ID:2476618

Gebhart, T. E. ^[1]; Meitner, S. J. ^[1]; Baylor, L. R. ^[1]; Herfindal, J. L. ^[1]; Jachmich, S. ^[2]; Lehnen, M. ^[2]; Kruezi, U. ^[2]; Wilson, J. ^[3]; Craven, D. ^[3]; Peacock, A. ^[3]

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1. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
2. ITER Organization, St. Paul Lez Durance (France)
3. UK Atomic Energy Authority (UKAEA), Culham (United Kingdom). Culham Centre for Fusion Energy (CCFE)

Shattered pellet injection (SPI) experiments on Joint European Torus (JET) are an important element in determining the physics basis for mitigating disruptions in ITER. Here, the initial design of the JET SPI system included three barrels to produce pellets with diameters of 4.5, 8.1, and 12.5 mm. The variability of the pellet speed by operating with and without a mechanical punch was limited and led to poor pellet integrity, so the mechanical punch was removed. Fragment size distribution is a function of pellet speed and the desire to change the resulting fragment size distribution was not originally a requirement. After the first set of SPI experiments on JET, different pellet sizes were considered to enable dual injection experiments with identical pellet diameters. It was also determined that speed control is necessary to improve experimental repeatability and to determine how the fragment size distribution impacts mitigation performance. Two barrels were fabricated to form pellets of 10 mm diameter and a third to form an 8.1 mm diameter pellet. New propellant valves were also fabricated and characterized to improve repeatability and overall performance. To have fine control of pellet speed, inserts to reduce the breech volume were fabricated and installed. Laboratory testing was conducted to ensure pellet release and provide a comparison of propellant gas delivered versus pellet speeds for a range of pellet types and mixtures. This article will also discuss how lessons learned from the JET SPI modifications can be applied to other SPI systems, such as the ITER SPI system, as controlling pellet release with the least amount of propellant gas is essential for optimal SPI effectiveness.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 2476618
• Journal Information: IEEE Transactions on Plasma Science, Journal Name: IEEE Transactions on Plasma Science Journal Issue: 9 Vol. 52; ISSN 0093-3813
• Publisher: IEEE
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY