Studies of the plasma vertical instability and its stabilized concepts in JA and EU broader approach, DEMO design activity

Utoh, Hiroyasu; Tokunaga, Shinsuke; Asakura, N.; Sakamoto, Y.; Someya, Youji; Hiwatari, Ryoji; Tobita, K.; Federici, G.; Wenninger, R.; Maviglia, F.; Albanese, R.; Ambrosino, R.; Mattei, M.; Villone, F.

doi:10.1016/j.fusengdes.2018.04.026

Cited by 5 publications

(4 citation statements)

References 12 publications

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“…The interested reader is referred to [12,13] for a comprehensive description of the assumptions in the code. Plots of the operational space at aspect ratio A = 2.6, 3.1, 3.6 (with respective elongations κ 95 = 1.70, 1.65, 1.56-these values originate from an analysis carried out with the method described in [40]) are shown in figure 3. For these cases, fusion power was kept constant at 2000 MW as in the EU-DEMO reference assumed in this work, but the pulse length was allowed to vary, its lowest limit having been fixes at 1.33 h. These plots include the maximum field on the TF coils for reference (dotted lines).…”

Section: Effect Of Aspect Ratio and Shapementioning

confidence: 99%

Figure of merit for divertor protection in the preliminary design of the EU-DEMO reactor

Siccinio

Federici²,

Kembleton

et al. 2019

Nucl. Fusion

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This paper discusses the criteria to be used in the preliminary design phases of the EU-DEMO reactor to ensure the performance of the divertor without compromising the stability of core plasma or the fusion power generation. This work refers to a lower single null conventional divertor using actively cooled solid metal plasma-facing components and with extrinsic seeding for heat flux dissipation, which is the solution currently adopted for EU-DEMO. The analysis does not consider the role of the Edge Localised Modes (ELMs), and also neglects major offnormal events like disruptions. It is shown that it is necessary to fulfil two high-level requirements, namely: i) the concentration of seeded impurities has to be lower than some critical value in order not to compromise the fusion plasma performance or stability and ii) damage to the divertor plate in case of accidental plasma reattachment must be avoided for a time sufficiently long to ensure a safe, controlled termination of the plasma discharge, as, in a device like EU-DEMO, other strategies relying on mass injection are considered more likely to cause a loss of plasma stability at full current, with dramatic consequences for the integrity of plasma facing components. Two figures of merit, corresponding to these criteria, have been identified in the existing literature and discussed. The dependence of such figures of merit on the relevant machine parameters (major radius and toroidal magnetic field) is analysed. Initially, the analysis is carried out using a simple 0D physics approach and subsequently by means of the systems code PROCESS, which allows for consideration of further parameters, such as aspect ratio and elongation. The main conclusion of the present work is that the simultaneous fulfilment of both requirements limits the viable EU-DEMO size both in terms of major radius 𝑅 and in terms of toroidal magnetic field 𝐵 𝑇 . Finally, an attempt to extend the EU-DEMO related conclusions to a more general level is made.

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Section: Effect Of Aspect Ratio and Shapementioning

confidence: 99%

Figure of merit for divertor protection in the preliminary design of the EU-DEMO reactor

Siccinio

Federici²,

Kembleton

et al. 2019

Nucl. Fusion

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“…The higher-κ proposal was based on improvement of the conducting shell design, i.e. increasing the electrical conductance (shell width) and installation also behind the inboard breeding blanket modules [12]. Increasing I p also improved the plasma performance such as P fusion and τ E , thus reduction of P sep to 258 MW with comparable plasma performance (HH 98y2 ∼ 1.3, β N ∼ 3.4) was obtained at higher c Ar main ∼ 6 × 10 −3 , as shown in figure 1.…”

Section: Plasma Design For Power Exhaust Scenariosmentioning

confidence: 99%

Power exhaust concepts and divertor designs for Japanese and European DEMO fusion reactors

et al. 2021

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Concepts of the power exhaust and divertor design have been developed, with a high priority in the pre-conceptual design phase of the Japan–Europe broader approach DEMO design activity (BA DDA). Common critical issues are the large power exhaust and its fraction in the main plasma and divertor by the radiative cooling (P rad tot/P heat ⩾ 0.8). Different exhaust concepts in the main plasma and divertor have been developed for Japanese (JA) and European (EU) DEMOs. JA proposed a conventional closed divertor geometry to challenge large P sep/R p handling of 30–35 MW m−1 in order to maintain the radiation fraction in the main plasma at the ITER-level (f rad main = P rad main/P heat ∼ 0.4) and higher plasma performance. EU challenged both increasing f rad main to ∼0.65 and handling the ITER-level P sep/R p in the open divertor geometry. Power exhaust simulations have been performed by SONIC (JA) and SOLPS5.1 (EU) with corresponding P sep = 250–300 MW and 150–200 MW, respectively. Both results showed that large divertor radiation fraction (P rad div/P sep ⩾ 0.8) was required to reduce both peak q target (⩽10 MW m−2) and T e,i div. In addition, the JA divertor performance with EU-reference P sep of 150 MW showed benefit of the closed geometry to reduce the peak q target and T e,i div near the separatrix, and to produce the partial detachment. Integrated designs of the water cooled divertor target, cassette and coolant pipe routing have been developed in both EU and JA, based on the tungsten (W) monoblock concept with Cu-alloy pipe. For year-long operation, DEMO-specific risks such as radiation embrittlement of Cu-interlayers and Cu-alloy cooling pipe were recognized, and both foresee higher water temperature (130 °C–200 °C) compared to that for ITER. At the same time, several improved technologies of high heat flux components have been developed in EU, and different heat sink design, i.e. Cu-alloy cooling pipes for targets and RAFM steel ones for the baffle, dome and cassette, was proposed in JA. The two approaches provide important case-studies of the DEMO divertor, and will significantly contribute to both DEMO designs.

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“…This is mainly due to the presence of a thick Breeding Blanket (BB) system [1,2] placed between the plasma and the Poloidal Field (PF) coils, used as actuators for active plasma vertical stabilization purposes. The large PF Coils-plasma distance also implies a less effective passive stabilization effect of the Vacuum Vessel (VV) [3], resulting in an increase of the power needed to control the plasma vertical position, especially in the case of off-normal operations inducing significant variations of the plasma internal parameters. Moreover, even if the present DEMO BB concept design can withstand heat loads compatible with the foreseen steady state and controllable transient conditions [4], greater challenges arise from the occurrence of severe off-normal events like VDEs [5,6].…”

Section: Introductionmentioning

confidence: 99%

Inter-machine plasma perturbation studies in EU-DEMO relevant scenarios: lessons learnt for EM forces prediction during VDEs

et al. 2022

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To support the deployment of DEMO wall protection strategy, the development of comprehensive analyses is essential to understand the implications of transient perturbations on the plasma shape control and on the vertical stability, some of the most critical aspects to be considered in elongated plasmas. Therefore, the design activities of the DEMO limiter structures need the deep understanding of the effects induced by transient plasma perturbations coupled with one of the most severe load conditions occurring in tokamaks, the Vertical Displacement Event (VDE). Since Electromagnetic (EM) loads during VDE phases are among the DEMO limiters design drivers, this study focuses on predictive simulations of the final plasma position and of EM loads following a VDE. For this purpose, a multi-tokamaks study supported by the construction of an inter-machine database containing experimental transient plasma perturbations and VDEs from JET and ASDEX Upgrade (AUG) has been carried out. It aims at the characterization of some transient plasma perturbations that may lead to high control efforts by the vertical stability system in terms of variations of the plasma internal parameters and vertical displacements. Consequently, such experimental transient plasma perturbations have been properly scaled to DEMO reference geometries with different magnetic configurations, to be simulated in terms of plasma dynamical behaviour by means of MAXFEA code. Finally, initial predictive EM loads on DEMO limiter structures will be discussed in the case of VDEs following plasma perturbations.

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Studies of the plasma vertical instability and its stabilized concepts in JA and EU broader approach, DEMO design activity

Cited by 5 publications

References 12 publications

Figure of merit for divertor protection in the preliminary design of the EU-DEMO reactor

Figure of merit for divertor protection in the preliminary design of the EU-DEMO reactor

Power exhaust concepts and divertor designs for Japanese and European DEMO fusion reactors

Inter-machine plasma perturbation studies in EU-DEMO relevant scenarios: lessons learnt for EM forces prediction during VDEs

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