Wall protection strategies for DEMO plasma transients

Maviglia, F.; Albanese, R.; Ambrosino, R.; Arter, W.; Bachmann, C.; Barrett, T.; Federici, G.; Firdaous, M.; Gerardin, J.; Kovari, M.; Loschiavo, V. P.; Mattei, M.; Villone, F.; Wenninger, R.

doi:10.1016/j.fusengdes.2018.02.064

Cited by 44 publications

(40 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…If adequate provisions are not included in the design, a few occurrences of plasma transient events may severely damage the first wall or even lead to a breach of the cooling pipes and a consequent loss of coolant. Preliminary results of the work commenced to address this problem are described elsewhere [23]. KDII/2-It is generally agreed that water should be considered as the divertor coolant for DEMO design as the divertor surface heat flux conditions prove to be beyond present helium power handling capabilities [24].…”

Section: Key Design Integration Issuesmentioning

confidence: 99%

Overview of the DEMO staged design approach in Europe

Federici¹,

Bachmann²,

et al. 2019

Self Cite

View full text Add to dashboard Cite

This paper describes the status of the pre-conceptual design activities in Europe to advance the technical basis of the design of a DEMOnstration Fusion Power Plant (DEMO) to come in operation around the middle of this century with the main aims of demonstrating the production of few hundred MWs of net electricity, the feasibility of operation with a closedtritium fuel cycle, and maintenance systems capable of achieving adequate plant availability. This is expected to benefit as much as possible from the ITER experience, in terms of design, licensing, and construction. Emphasis is on an integrated design approach, based on system engineering, which provides a clear path for urgent R&D and addresses the main design integration issues by taking account critical systems interdependencies and inherent uncertainties of important design assumptions (physics and technology). A design readiness evaluation, together with a technology maturation and down selection strategy are planned through structured and transparent Gate Reviews. By embedding industry experience in the design from the beginning it will ensure that early attention is given to technology readiness and industrial feasibility, costs, maintenance, power conversion, nuclear safety and licensing aspects.

show abstract

Section: Key Design Integration Issuesmentioning

confidence: 99%

Overview of the DEMO staged design approach in Europe

Federici¹,

Bachmann²,

et al. 2019

Self Cite

View full text Add to dashboard Cite

show abstract

“…Because of the necessity of breeding tritium, the EU-DEMO wall must be sufficiently thin to allow the fusion generated neutrons reaching the breeding region. The present first wall design foresees in fact a ~3 mm metal layer (W and EUROFER) between the vacuum chamber and the coolant (water or He) [17,18]. Such weak wall cannot withstand a contact with the plasma, unless the stored (kinetic and magnetic) energy is extremely lowat least a factor of 10 below the flat-top values.…”

Section: Divertor Reattachmentmentioning

confidence: 99%

“…Such weak wall cannot withstand a contact with the plasma, unless the stored (kinetic and magnetic) energy is extremely lowat least a factor of 10 below the flat-top values. Even the foreseen sacrificial limiters for the wall protection during incidental plasma-wall contacts [19] would be damaged if ~5 MA, whereas 20 MA during the flattop phase. Thus, any emergency plasma shutdown procedure which relies on a plasma/wall contact, or in general on a loss of plasma control at high current, is not considered viable, as the consequences for the first wall might be too severe.…”

Section: Divertor Reattachmentmentioning

confidence: 99%

DEMO physics challenges beyond ITER

Siccinio

Biel

Cavedon

et al. 2020

Fusion Engineering and Design

Self Cite

View full text Add to dashboard Cite

For electricity producing tokamak fusion reactors like EU-DEMO, it is prudent to choose a plasma scenario close to the ITER baseline, where the largest amount of experimental evidence is available. Nevertheless, there are some aspects in which ITER and EU-DEMO have to differ, as the simple exercise of up-scaling from ITER to a larger device is constrained both by physical nonlinearities and by technological limits. In this work, relevant differences between ITER and the current EU-DEMO baseline in terms of plasma scenario are discussed. Firstly, EU-DEMO is assumed to operate with a very large amount of radiative power originating both from the scrape-off layer and, markedly, from the core. This radiation level is obtained by means of seeded impurities, whose presence significantly affects many aspects of the scenario itself, especially in terms of transient control. Secondly, because of the need of breeding tritium, the EU-DEMO wall is less robust than the ITER one. This implies that every offnormal interruption of the plasma discharge, for example in presence of a divertor reattachment, cannot rely on fastshutdown procedures finally triggering a loss of plasma control at high current, but other strategies need to be developed. Thirdly, the ITER method for the control of the so-called sawteeth (ST) has been shown to be too expensive in terms of auxiliary power requirements, thus other solutions have to be explored. Finally, the problem of actively mitigating, or suppressing, the Edge Localised Modes (ELMs) has recently increased the interest on naturally ELM-free regimes (like QH-mode, I-mode, and also negative triangularity) for EU-DEMO, thus increasing the needs for ELM mitigation or suppression with respect to the approach adopted in ITER.

show abstract

“…Neutronic simulations have been carried out using MCNP6.1 [18] and JEFF-3.3 nuclear data library [19] on a 22.5° DEMO baseline 2017 model. A feature of the 2017 design is a reduction in radial thickness of the blanket segments (which are now 560 mm inboard and 800 mm outboard) compared to the previous 2015 baseline DEMO design, motivated by improving vertical stability [4]. The 2017 baseline model is a generic one in which the breeding zone cells are empty, hence a homogenized material mix was used.…”

Section: Preliminary Calculation Of the Impact On Tritium Breedingmentioning

confidence: 99%

“…During the flat-top phase, the plasma is in a diverted configuration and the majority of power in the scrape-offlayer is conducted into the divertor zone, with only a fraction being conducted to the wall [4]. Nevertheless, the anticipated blanket FW technology described above has a modest steady-state engineering heat flux limit of approximately 1 MW/m 2 [2] (for water or helium cooling).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Wall protection strategies for DEMO plasma transients

Cited by 44 publications

References 17 publications

Overview of the DEMO staged design approach in Europe

Overview of the DEMO staged design approach in Europe

DEMO physics challenges beyond ITER

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

Contact Info

Product

Resources

About