Pressure Response Optimization of an Eddy Current-Driven Flyer Plate Valve for the ITER Shattered Pellet Injection System

Ghiozzi, A.G.; Velez, D. A.; Gebhart, T. E.; Gehrig, Monica; Ericson, M.N.; Baylor, L. R.; Rasmussen, D. A.

doi:10.1080/15361055.2021.1906149

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…ITER-sized hydrogen and deuterium pellets require 1530 and 2800 N for release. Computational fluid dynamics (CFD) modeling of the ITER prototype propellant valve, known as the flyer plate valve (FPV), was performed to calculate the force applied to the pellet face from the impinging high-pressure gas [13]. Experiments have shown that deuterium pellets at 8 K do not release when using the FPV with 60 bar propellent gas pressure, even though the CFD results indicate that required forces are marginally met.…”

Section: Scaling Pellet Release Forcesmentioning

confidence: 99%

Recent progress in shattered pellet injection technology in support of the ITER disruption mitigation system ^*

et al. 2021

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Shattered pellet injection (SPI) has been selected as the baseline technology for the disruption mitigation (DM) system for ITER. Typical SPI utilizes cryogenic cooling to desublimate low pressure (<100 mbar) gases onto a cold zone within a pipe gun barrel, forming a cylindrical pellet. Pellets are dislodged from the barrel and accelerated using either a gas driven mechanical punch or high-pressure light-gas delivered by a fast-opening valve. SPI technology developed at Oak Ridge National Laboratory is currently deployed and operational on DIII-D, JET, and KSTAR. These SPI systems are used in experiments for physics scaling to ITER thermal mitigation and runaway electron dissipation/avoidance. The pellet sizes used for these machines are in the range of 4 to 12.5 mm in diameter with length to diameter ratios (L/D) of ∼1.5. The current plan for ITER SPI is to utilize pellets that are 28.5 mm in diameter with an L/D of ∼2. The large pellet sizes, high steady-state magnetic fields, and limitations of operating in a radiation environment render much of the current technology unusable. In addition to technology improvements, a deeper understanding of pellet material properties, formation, and release is being developed for implementation in future SPI designs, specifically ITER.

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Section: Scaling Pellet Release Forcesmentioning

confidence: 99%

Recent progress in shattered pellet injection technology in support of the ITER disruption mitigation system ^*

et al. 2021

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Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system

Gebhart,

Baylor,

Dibon

et al. 2024

Nucl. Fusion

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Studies have been performed on the release mechanism for large pellets using high pressure gas in a shattered pellet injector. Typically, pellets are dislodged from the cryogenic surface and accelerated down a barrel using high pressure gas delivered by a fast-acting propellant valve. The pellets impact an angled surface which shatters the pellet into many small fragments before entering the plasma. This technique was initially demonstrated on DIII-D and is now deployed on JET, KSTAR, ASDEX-Upgrade, and other tokamaks around the world in support of ITER’s disruption mitigation system design and physics basis. The large hydrogen, 28.5 mm diameter, 2 length-to-diameter ratio, pellets foreseen for ITER SPI operation have low material strength and low heat of sublimation, which cause the pellets to be fragile and highly reactive to the impact of warm propellant gas. Due to the size of the pellets, significantly more propellant gas is required to dislodge and accelerate them. This creates a potentially significant propellant gas removal issue as 2 to 6 bar-L of gas is expected to be required for release and speed control. The research presented in this paper is an in-depth exploration of the parameters that are keys to reliable pellet release and speed control. Computational fluid dynamics (CFD) modeling of propellant flows through various breech designs was conducted to determine the force generated on the back surface of a pellet. These simulations assumed the use of the ORNL designed flyer plate valve. CFD modeling combined with experimental measurements provide adequate insight to determine a path to an optimal valve and breech design for ITER SPI pellet release and speed control while minimizing propellant gas usage.

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Pressure Response Optimization of an Eddy Current-Driven Flyer Plate Valve for the ITER Shattered Pellet Injection System

Cited by 2 publications

References 3 publications

Recent progress in shattered pellet injection technology in support of the ITER disruption mitigation system ^*

Recent progress in shattered pellet injection technology in support of the ITER disruption mitigation system ^*

Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system

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Pressure Response Optimization of an Eddy Current-Driven Flyer Plate Valve for the ITER Shattered Pellet Injection System

Cited by 2 publications

References 3 publications

Recent progress in shattered pellet injection technology in support of the ITER disruption mitigation system *

Recent progress in shattered pellet injection technology in support of the ITER disruption mitigation system *

Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system

Contact Info

Product

Resources

About

Recent progress in shattered pellet injection technology in support of the ITER disruption mitigation system ^*

Recent progress in shattered pellet injection technology in support of the ITER disruption mitigation system ^*