The development and testing of the thermal break divertor monoblock target design delivering 20 MW m<sup>−2</sup> heat load capability

Fursdon, M.; Barrett, T.; Domptail, F.; Evans, Llion; Luzginova, N.V.; Greuner, N. H.; You, J.-H.; Li, Muyuan; Richou, M.; Gallay, F.; Visca, E.

doi:10.1088/1402-4896/aa8c8e

Cited by 28 publications

(23 citation statements)

References 14 publications

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“…Among others, two concepts, namely Thermal Break Interlayer (TBI) and Thin Graded Interlayer (TGI), have been developed and compared to the baseline reference of water-cooled divertor targets (ITER-like, IL). In the TBI concept [4], being developed at CCFE, the copper interlayer presents 6 radial spokes at the HHF side, as well as an additional groove on the low flux side at the axis of symmetry. In this way, the interlayer acts as a thermal barrier that helps the repartition, around the circumference of the pipe, of the heat flux that would otherwise intensify on the plasma-facing side of the heat sink.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic analysis of tungsten monoblock divertor mock-ups after high heat flux test

Dose

Roccella

Richou

et al. 2019

Fusion Engineering and Design

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In this paper, a comparison is presented among the ultrasonic measures of different W-monoblock mock-ups following high heat flux tests. The DEMO reference solution for the divertor targets (ITER-like) is compared with two other concepts, in which the interlayer between monoblocks and tube has been engineered to increase the performance of the component (Thermal Break Interlayer, Thin Graded Interlayer). Ultrasonic measurements have been performed at the depths of interest. The reflected signal amplitude and time of flight at defined depths are used to determine the shape and entity of the defect, when present. For each concept, the most frequently observed defects due to thermal loading are then identified. Preliminary post-mortem analysis confirms the results from the ultrasonic tests, proving the defect imaging capability of such non-destructive technique for advanced W-monoblock concepts.

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Section: Introductionmentioning

confidence: 99%

Ultrasonic analysis of tungsten monoblock divertor mock-ups after high heat flux test

Dose

Roccella

Richou

et al. 2019

Fusion Engineering and Design

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“…The braze process simulated by the elasto-plastic model is that described by Fursdon [16]. In this, a 1mm copper interlayer is first cast onto the bore of the tungsten blocks.…”

Section: Simulation Methodologymentioning

confidence: 99%

A hybrid analysis procedure enabling elastic design rule assessment of monoblock-type divertor components

Fursdon

You

Barrett

et al. 2018

Fusion Engineering and Design

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This paper presents a simplified rule-based elastic analysis procedure (and its rationale) for the structural integrity assessment of the structural pipe component within monoblock divertor plasma facing components (components constructed from a tungsten block with through cooling pipe and copper interlayer). It is first demonstrated that the conventional fully elastic finite element analysis method used in an elastic code rule assessment must be modified when applied to monoblocks to overcome the problems caused by the assembly of multiple materials (with different yield strengths and different coefficients of thermal expansion causing residual stress). This is done by comparing the result of a fully elastic model with a more representative elasto-plastic model incorporating residual stress simulation. The results show that due to the expected high levels of residual stress, the desired elastic modelling of the structural pipe component can only be used to determine cyclic stress range (but not absolute stress), and even then, only if accompanied by elasto-plastic simulation of the non-structural interlayer (to apply the correct levels of differential expansion loads from the tungsten). This mixed elastic-elasto-plastic method is used in the proposed procedure, and applies the elastic code rules employing cyclic stress range, i.e. rules for ratchetting and fatigue. Additional rules for critical heat flux and allowable material temperatures are added. Example results of an assessment using the procedure are also presented for an ITER-like monoblock divertor target component.

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“…The primary cause of failure in prototype divertor components has been the interface between the structure (in most cases CuCrZr) and the tungsten armour [39]. Pure copper is used in ITER as a ductile interlayer to mitigate this, and concepts employing more complex compliant or graded structures have also been proposed for DEMO [40,41]. At the same time, alternative materials with lower thermal mismatches are being explored, including chromium [42].…”

Section: Thermal Mismatch Stressmentioning

confidence: 99%

“…For these dissimilar metal joints, ductility is a desirable characteristic as detailed above, and the inclusion of a ductile pure copper interlayer is the usual mitigation technique. Newer concepts involving compliant structures have also shown the ability to survive large numbers of cycles at elevated heat fluxes [40]. Novel thermal cycling methods for brazing dissimilar materials [44] have also been proposed for reducing these stresses in operation.…”

Section: Joiningmentioning

confidence: 99%

Refractory metals as structural materials for fusion high heat flux components

Hancock

Homfray

Porton

et al. 2018

Journal of Nuclear Materials

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Tungsten is the favoured armour material for plasma facing components for future fusion reactors, but studies examining the use of tungsten or other refractory metals in the underlying cooled structures have historically excluded them, leaving current concepts heavily dependent on copper alloys such as copper chrome zirconium. This paper first outlines the challenge of selecting an appropriate alternative material for this application, with reference to historical selection methodology and design solutions, and then reexamines the use of refractory metals in the light of current design priorities and manufacturing techniques. The rationale for considering refractory alloys as structural materials is discussed, showing how this is the result of relatively small changes to the logic previously applied, with a greater emphasis on high temperature operation, a re-evaluation of current costs, a relaxation of absolute activation limits, and the availability of advanced manufacturing techniques such as additive manufacturing. A set of qualitative and quantitative assessment criteria are proposed, drawing on the requirements detailed in the first section; including thermal and mechanical performance, radiation damage tolerance, manufacturability, and cost and availability. Considering these criteria in parallel rather than sequence gives a less binary approach to material selection and instead provides a strengths and weaknesses based summary from which more nuanced conclusions can be drawn. Data on relevant material properties for a range of candidate materials, including elemental refractory metals and a selection of related alloys are gathered from a range of sources and collated using a newly developed set of tools written in the python language. These tools are then used to apply the aforementioned assessment criteria and display the results. The lack of relevant data for a number of promising materials is highlighted, and although a conclusive best material cannot be identified, refractory alloys in general are proposed as worthy of further investigation.

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The development and testing of the thermal break divertor monoblock target design delivering 20 MW m⁻² heat load capability

Cited by 28 publications

References 14 publications

Ultrasonic analysis of tungsten monoblock divertor mock-ups after high heat flux test

Ultrasonic analysis of tungsten monoblock divertor mock-ups after high heat flux test

A hybrid analysis procedure enabling elastic design rule assessment of monoblock-type divertor components

Refractory metals as structural materials for fusion high heat flux components

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The development and testing of the thermal break divertor monoblock target design delivering 20 MW m−2 heat load capability

Cited by 28 publications

References 14 publications

Ultrasonic analysis of tungsten monoblock divertor mock-ups after high heat flux test

Ultrasonic analysis of tungsten monoblock divertor mock-ups after high heat flux test

A hybrid analysis procedure enabling elastic design rule assessment of monoblock-type divertor components

Refractory metals as structural materials for fusion high heat flux components

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Product

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The development and testing of the thermal break divertor monoblock target design delivering 20 MW m⁻² heat load capability