Exposure of liquid lithium confined in a capillary structure to high plasma fluxes in PILOT-PSI—Influence of temperature on D retention

Martín-Rojo, A.B.; Oyarzábal, E.; Morgan, T.W.; Tabarés, F.L.

doi:10.1016/j.fusengdes.2016.08.008

Cited by 12 publications

(7 citation statements)

References 8 publications

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“…Baldwin claimed that at temperatures below the melting temperature of the hydride or deuteride salt, the initial hydrogen release (desorption period 1) was due to the evolution of hydrogen from the α phase, and the following release of hydrogen (desorption period 2), at temperatures near the melting point, was due to dissolution of, and subsequent evolution from, the β phase. Similar observations for desorption behavior have been reported in several other studies [6,9,10,12,13], all of which identified two distinct evolution rates. Identification of these desorption periods is vital for back-end tritium recovery efforts.…”

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confidence: 89%

A study on hydrogen absorption and dissolution in liquid lithium

et al. 2019

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Methods that plan to recover tritium from liquid lithium require intimate knowledge of the surface, sub-surface, and bulk chemistry associated with the interactions between hydrogen isotopes and lithium particles. Focusing on the lithium–lithium hydride system, previous studies have been able to determine concentrations associated with the liquidus curve, which separates the hydrogen dissolved in solution (known as the phase) from the hydrogen which precipitates out as lithium hydride (known as the phase). Knowledge of how these phases coexist in bulk melts is particularly important when the lithium is exposed to a hydrogen, deuterium, or tritium plasma, because they govern how quickly one can recover these isotopes in back-end processes for future lithium-walled fusion reactors. To this end, lithium samples were exposed to hydrogen plasmas in the Tungsten Fuzz Characterization of Nanofeatures (TUFCON) chamber at the University of Illinois. Each lithium sample was varied with respect to sample temperature, applied electrical bias, and length of sample exposure, and in each there coexisted a combination of the and phases. In all cases, two distinct absorption periods were observed during exposure. Similarly, two distinct desorption periods were observed during temperature-programmed desorption (TPD) scans. While similar desorption periods have been observed in the literature, changes in sample resistivity measured in the current study help to validate this behavior from a novel, condensed-phase perspective. The results of lithium exposures in TUFCON will be presented, along with a discussion on how the exposure conditions and phases affect recovery. Observations of superficial surface layers, and how they affect absorption and desorption, will be included in these discussions. How these results, along with the resultant marginally-enhanced dissolution behavior, can extend to tritium recycling efforts will also be explored.

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confidence: 89%

A study on hydrogen absorption and dissolution in liquid lithium

et al. 2019

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“…The lithium research as an alternative PFM has been addressed in a wide variety of experiments involving hot plasma devices [3][4][5][6][7][8][9], linear plasma facilities [10,11], laboratory configurations [12,13] and innovative concepts for future fusion devices [14,15] …”

Section: Introductionmentioning

confidence: 99%

Hydrogen retention studies on lithiated tungsten exposed to glow discharge plasmas under varying lithiation environments using Thermal Desorption Spectroscopy and mass spectrometry

Castro

Valson

Tabarés

2017

Fusion Engineering and Design

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“…The incoming deuterium flux density in this work is ∼ 10 24 m −2 s −1 . That is 1 to 5 orders of magnitude higher than in [24,32] respectively, and might explain why the LiD layer is observed to disappear at a relatively higher temperature. Therefore it is recommended to conduct experiments where the target temperature can be controlled independently of the incoming particle flux density, where discharges are applied over longer periods of time to reach a steady state, and where the LiD concentration in the target can be monitored.…”

Section: The Impact Of Lid Formation On the Thermal Operating Window ...mentioning

confidence: 87%

“…In previous work it has been demonstrated that deuterium is no longer trapped above ∼ 500 • C, under a deuterium flux of 2.5 × 10 19 m −2 s −1 [24]. Experiments from [32], where a particle flux density of ∼ 10 23 m −2 s −1 was applied, indicated that deuterium is indeed desorbed from Li above ∼ 500 • C. However, desorption rates and deuterium concentrations after plasma exposures could not be determined. These conflicting observations must be reconciled.…”

Section: The Impact Of Lid Formation On the Thermal Operating Window ...mentioning

confidence: 98%

Performance of liquid-lithium-filled 3D-printed tungsten divertor targets under deuterium loading with ELM-like pulses in Magnum-PSI

et al. 2021

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A fusion reactor divertor must withstand heat flux densities <10 MW m−2. Additionally, it may have to withstand millisecond pulses on the order of 0.5 to 30 MJ m−2 due to (mitigated) edge-localized modes (ELM) occurring with 30 to 60 Hz. We investigate if these requirements can be met by capillary porous system (CPS) liquid lithium divertors (LLD). 3D-printed tungsten CPS targets were exposed in the linear plasma device Magnum-PSI, to deuterium plasma discharges lasting 15 s, generating 1.5 to 16 MW m−2, and T e ∼ 1.5 eV. Additionally, ELM-like pulses were superimposed on top of the steady state for 3 s with a frequency of 2 and 100 Hz, power flux densities of 0.3 to 1 GW m−2, and T e up to ∼14 eV. All Li targets survived without damage. The surface temperature (T s) was locked at ∼850 °C, which was attributed to power dissipation via vapor shielding. Meanwhile, unfilled reference targets melted during the severest pulsed loading. A blue grayish layer of presumably LiD formed when T s < 500 °C, but disappeared when the locking temperature was reached. This implies that LiD formation can be avoided, but that it may require a surface temperature at which Li evaporation excessively contaminates the core plasma in a tokamak. During pulsed loading the plasma facing surface remained wetted in all conditions. Bolometry indicated that, only during pulses, there was a large increase in radiative power dissipation compared to targets without Li. A high speed camera with a Li-I filter showed that strong Li evaporation continued up to 5 ms after a pulse. Overall, the liquid-lithium-filled 3D-printed tungsten targets were found to be highly robust, and 3D-printing can be considered as a promising manufacturing technique for LLDs. Further research is needed particularly on the formation of LiD and the associated tritium retention, as well as the impact of enhanced evaporation during and after ELMs on the core plasma.

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Exposure of liquid lithium confined in a capillary structure to high plasma fluxes in PILOT-PSI—Influence of temperature on D retention

Cited by 12 publications

References 8 publications

A study on hydrogen absorption and dissolution in liquid lithium

A study on hydrogen absorption and dissolution in liquid lithium

Hydrogen retention studies on lithiated tungsten exposed to glow discharge plasmas under varying lithiation environments using Thermal Desorption Spectroscopy and mass spectrometry

Performance of liquid-lithium-filled 3D-printed tungsten divertor targets under deuterium loading with ELM-like pulses in Magnum-PSI

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