Simulations of ITER start-up and assessment of limiter power loads

Federici, G.; Золотухин, О. В.; Kobayashi, Masahiro; Loarte, A.; Strohmayer, G.; Tanga, A.; Portone, A.; Horton, L. D.; Feng, Y.; Sardei, F.; Gribov, Y.; Shimada, M.; Polevoi, A.; Mitteau, R.; Lowry, C.

doi:10.1016/j.jnucmat.2007.01.260

Cited by 13 publications

(22 citation statements)

References 12 publications

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“…A rough estimate of the degree to which the limiters in Tore Supra achieve that approximation can be assessed by means of a simple geometrical criterion proposed originally by Stangeby et al [63] for a set of discrete limiters redistributed equidistantly in the toroidal direction. The discrete outboard limiters will act, in effect, as a toroidally continuous limiter (meaning that all field lines in the SOL strike some outboard (inboard) limiter on their first pass through the outboard (inboard) midplane) if λ provided by transport analysis [64][65][66]. The predictive capability of the scaling (3) to ITER is, however, very limited as the database (of the outboard-limited discharges in particular) is statistically insignificant.…”

Section: Parallel Heat Flux Density and Its Relation To Q λmentioning

confidence: 99%

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

Kočan¹,

Gunn

2010

Plasma Phys. Control. Fusion

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In the Tore Supra tokamak, the scrape-off layer profiles of discharges limited either on the inboard or on the outboard side are compared. Inboard-limited discharges are characterized by substantially longer SOL e-folding lengths of ion and electron temperatures and electron density measured near the top of the plasma, providing strong evidence that the ion and electron energy transport across the SOL is enhanced on the outboard side, similar to the particle transport. The parallel heat flux density extrapolated to the last closed flux surface is found to be inversely proportional to its e-folding length in the SOL. The outboard limiters thus receive higher and more peaked heat loads than the inboard limiters. These results are important for the optimization of the plasma start-up scenario and design of the first wall in ITER.PACS 52.25.Fi, 52.25.Xz, 52.35.Ra, 52.55.Fa, 52.70.Ds IntroductionIn tokamaks, the intermittent expulsion of magnetic-field-aligned plasma filaments from the last closed flux surface (LCFS) is responsible for a large fraction of the effective radial transport to the wall [1][2][3][4][5][6]. Filament propagation appears to be governed by a ballooning-type instability in the unfavourable magnetic curvature region on the low field side. As the filaments propagate outward, they also expand freely along the magnetic field lines, driving pressure-driven field-direction-independent parallel flows. Mach probe measurements in many divertor tokamaks (e.g. [7] and references therein) show flow patterns consistent with this model (i.e. stagnant flow poloidally approximately halfway between the outer midplane and the X-point), in which the filaments can be seen as an important particle source in the scrape-off layer (SOL). Similar observations in limiter tokamaks [8][9][10][11][12] prove that enhanced radial particle transport on the outboard side of the plasma is a universal phenomenon, independent of the presence of an X-point divertor. The enhancement of the radial particle transport on the outboard side of the limiter plasmas was confirmed by the 3D fluid turbulence code TOKAM-3D [13]. When the plasma contact point is on the inboard limiters, the filaments propagate freely out to the wall, filling all the available volume outside the LCFS and leading to a broad SOL with nearly flat density profiles. On the other hand, it was demonstrated [12] that outboard modular limiters suppress the radial particle transport when they are near the LCFS, leading to a very thin SOL. It is probable [8] that the limiters act as simple mechanical barriers that intercept the parallel particle flux in the region in which the enhanced radial convection.

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Section: Parallel Heat Flux Density and Its Relation To Q λmentioning

confidence: 99%

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

Kočan¹,

Gunn

2010

Plasma Phys. Control. Fusion

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“…This has to be kept in mind when interpreting experiments in non actively cooled devices. Finally, it should be noted that ITER will also be a long pulse experiment in limiter configuration during the plasma ramp up phase ($30 s) [13], which makes contribution from limiter machines also valuable (therefore light grey in Table 1). LHD, with its island divertor, is in a relevant plasma regime although in a quite different geometry and so also appears in light grey.…”

Section: Recent Achievements In Long Pulse Operationmentioning

confidence: 99%

Key plasma wall interaction issues towards steady state operation

Tsitrone

2007

Journal of Nuclear Materials

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“…However, the design should be tailored to the specific transient loading requirement of the start-up limiter. Based on ITER models [15], it is thought that the limited phase of plasma ramp-up will be approximately 60-100 s in duration. For this limited time the thermal inertia of tungsten may be exploited, resulting in a slightly thicker plasma-facing tungsten layer than would be chosen for purely steady-state loading.…”

Section: A Discrete Start-up Limitermentioning

confidence: 99%

Designs and technologies for plasma-facing wall protection in EU DEMO

et al. 2019

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The EU DEMO plasma is almost completely enveloped by large breeding blanket segments for tritium breeding and power extraction. Shaping of the blanket plasma-facing wall in 3-D may prove to be essential, but this strategy alone is not sufficient to protect against anticipated transient plasma events. The high heat flux wall-limiter approach used in ITER is not thought to be viable in a tritium self-sufficient power reactor, and so in EU DEMO wall protection using discrete limiters is pursued. Two types of discrete limiter are described in this paper. One is an equatorial port limiter designed to handle the power during the plasma start-up phase making use of water-cooled tungsten/CuCrZr monoblock technology. The second is the upper limiter, featuring a plasma-facing component designed specifically for extreme transient loading due to a vertical displacement event. The heat flux channeling and thermal barrier features of this design are shown to considerably reduce CuCrZr pipe temperature, and so reduce the likelihood of catastrophic failure. A preliminary neutronic calculation has shown that the impact of these discrete limiters on overall tritium breeding ratio is relatively low.

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Simulations of ITER start-up and assessment of limiter power loads

Cited by 13 publications

References 12 publications

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

Comparison of scrape-off layer profiles in outboard-versus inboard-limited plasmas in Tore Supra

Key plasma wall interaction issues towards steady state operation

Designs and technologies for plasma-facing wall protection in EU DEMO

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