Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system
Abstract
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 (Commaux et al 2016 Nucl. Fusion 56 046007) 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 2–6 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 keysmore »
- Authors:
-
[1];
[1];
[1];
[3];
[1];
[4];
[2];
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- ITER Organization, St. Paul Lez Durance (France)
- Columbia Univ., New York, NY (United States)
- General Atomics, San Diego, CA (United States)
- Univ. of Wisconsin, Madison, WI (United States)
- Publication Date:
- Research Org.:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 2305804
- Grant/Contract Number:
- AC05-00OR22725
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Nuclear Fusion
- Additional Journal Information:
- Journal Volume: 64; Journal Issue: 3; Journal ID: ISSN 0029-5515
- Publisher:
- IOP Science
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamak; disruption mitigation; shattered pellet injection
Citation Formats
Gebhart III, Trey E., Baylor, Larry R., Dibon, Mathias, Ericson, M. Nance, Felske, Eliot J., Frank, Shane S., Gardner, Walter L., Ghiozzi, Adriana G., Jachmich, Stefan, Kruezi, Uron, Lehnen, Michael, and Velez, Danah A. Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system. United States: N. p., 2024.
Web. doi:10.1088/1741-4326/ad2424.
Gebhart III, Trey E., Baylor, Larry R., Dibon, Mathias, Ericson, M. Nance, Felske, Eliot J., Frank, Shane S., Gardner, Walter L., Ghiozzi, Adriana G., Jachmich, Stefan, Kruezi, Uron, Lehnen, Michael, & Velez, Danah A. Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system. United States. https://doi.org/10.1088/1741-4326/ad2424
Gebhart III, Trey E., Baylor, Larry R., Dibon, Mathias, Ericson, M. Nance, Felske, Eliot J., Frank, Shane S., Gardner, Walter L., Ghiozzi, Adriana G., Jachmich, Stefan, Kruezi, Uron, Lehnen, Michael, and Velez, Danah A. Fri .
"Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system". United States. https://doi.org/10.1088/1741-4326/ad2424. https://www.osti.gov/servlets/purl/2305804.
@article{osti_2305804,
title = {Impact of breech geometry and propellant flow on the release of large pellets for the ITER disruption mitigation system},
author = {Gebhart III, Trey E. and Baylor, Larry R. and Dibon, Mathias and Ericson, M. Nance and Felske, Eliot J. and Frank, Shane S. and Gardner, Walter L. and Ghiozzi, Adriana G. and Jachmich, Stefan and Kruezi, Uron and Lehnen, Michael and Velez, Danah A.},
abstractNote = {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 (Commaux et al 2016 Nucl. Fusion 56 046007) 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 2–6 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.},
doi = {10.1088/1741-4326/ad2424},
journal = {Nuclear Fusion},
number = 3,
volume = 64,
place = {United States},
year = {Fri Feb 09 00:00:00 EST 2024},
month = {Fri Feb 09 00:00:00 EST 2024}
}
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