Influence of Fast Alpha Diffusion and Thermal Alpha Buildup on Tokamak Reactor Performance

Uckan, N. A.; Tolliver, Johnny S.; Houlberg, W. A.; Attenberger, S.E.

doi:10.13182/fst88-a25117

Cited by 27 publications

(17 citation statements)

References 15 publications

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“…Furthermore, by analysing the processes which determine T«, we have established a relationship between the exhaust efficiency, c p , the recycling coefficient, R, of the first wall system, the refuelling efficiency, 7, and the 'internal' and 'external' alpha particle confinement times, T Q1 and r a2 . The quantities € p , R and 7 and their combination describe the effective recycling of ash particles ( 4 He alone or both 4 He and p) back into the burn region because of imperfect pumping and shielding.…”

Section: Discussionmentioning

confidence: 99%

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Burn condition, helium particle confinement and exhaust efficiency

1990

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The burn condition for D-T plasmas is derived in a form which accounts for the stationary helium concentration determined by the coupling of the fusion power and helium production. The ratio of the global alpha particle confinement time r a to the energy confinement time T E is taken as a quantity characterizing the prevailing confinement and exhaust regime. For an ignited and stationary burning D-T plasma this ratio needs to remain sufficiently below 15 or below 10 for typical impurity concentrations. This poses a lower limit on the required helium exhaust efficiency and indicates that operational regimes are needed where the particle confinement time does not diverge too far from the energy confinement time. Applied to the D-3 He fusion reaction, the analysis leads to even more stringent limits on the ratio T'JT E , which must be smaller by a factor of three to four compared to the D-T case. It is found that, for any given temperature (and for otherwise equal exhaust and recycling conditions), in general burning can be achieved at two different values of the fusion parameter n T T E and ash concentration.

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Section: Discussionmentioning

confidence: 99%

“…Generation of helium -the ash of D-T fusion reactions -and its impact on pumping requirements, burn condition and minimum reactor size has already been considered in several publications (e.g. Refs [1][2][3][4][5][6][7]).…”

Section: Introductionmentioning

confidence: 99%

Burn condition, helium particle confinement and exhaust efficiency

1990

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“…Because the slowing down time τ s is inversely proportional to the plasma density, τ s ∼ n −1 e , the local values of n α /n e and β α /β, where n α and β α are the fast-α-particle density and beta values, respectively, with the total plasma beta value, depend only on the temperature (Uckan et al 1988). Both n α /n e and β α /β increase with the temperature (as shown in figure 1).…”

Section: Classical Physics Of Energetic-particle Confinement and Plasma Heatingmentioning

confidence: 99%

“…Figure 1. Local values of nα/ne and βα/β, for the case of Ti ∼ Te ∼ Tand Z eff = 1.5 (fromUckan et al 1988).2.0…”

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confidence: 99%

Alpha-particle physics in tokamaks

Putvinski

Heidbrink

Martín

et al. 1999

Philosophical Transactions of the Royal Society of London. Seri

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Efficient plasma heating by energetic fusion α-particles is a key element of achieving ignition or high fusion gain regimes (Q 1) in a tokamak reactor. The paper summarizes issues and reviews the latest theoretical and experimental results in the area of energetic particle physics in tokamaks.The discussion includes the classical physics of α-particle heating, effects of perturbations on a single-particle confinement, collective instabilities driven by energetic α-particles, description of the potential α-particle loss channels and their impact on a design of the plasma-facing components in a tokamak reactor.Most of the extrapolations to tokamak reactors are done with the use of ITER parameters and operational scenarios as an example.

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“…Uckan tt al. [6] have studied fast alpha diffusion and helium accumulation for TIBER and ETR in 1-1/2d. The dilution effect of impurities and helium ash were studied in 1-d simulations of ignited plasnu^s for INTOR by Singer [7] and in 1-1/2-d simulations for CIT by Stot]c: and…”

Section: Thus In Steady-state R P H T /R E = {Njn^ec/skt:)mentioning

confidence: 99%

Influence of MHD effects and edge conditions on ITER helium ash accumulation and sustained ignition

Redi

Cohen

1990

Journal of Nuclear Materials

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Dilution of reacting species by build-up of helium ash and its effect on ignition in the ITER tokamak have been studied in a series of simulations with the one-dimensional BALDUR transport code. Thermal diffusivities, obtained from ITER scaling laws and with radial variations observed in JET, gave rg s= 2-4 sec. Refuelling of deuterium and tritium maintained constant electron density, while carbon recycling was 1009c and the helium ash recycling was varied from 1.0 to 0.5, Including MHD effects, specifically sawteeth and beta limits, we find that ignition can be sustained for 200 seconds with Rhmii um = 0.95. These simulations, the only non-zerodimensional, time-dependent simulations thus far made for ITER plasmas, emphasize that edge plasma conditions, MHD behavior, and helium particle transport are critical syner gistic issues for sustained ignition.

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Influence of Fast Alpha Diffusion and Thermal Alpha Buildup on Tokamak Reactor Performance

Cited by 27 publications

References 15 publications

Burn condition, helium particle confinement and exhaust efficiency

Burn condition, helium particle confinement and exhaust efficiency

Alpha-particle physics in tokamaks

Influence of MHD effects and edge conditions on ITER helium ash accumulation and sustained ignition

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