Long-term fuel retention in JET ITER-like wall

Heinola, K.; Widdowson, A.; Likonen, J.; Alves, E.; Baron-Wiechec, A.; Brezinsek, S.; Catarino, N.; Coad, P.; Koivuranta, S.; Krat, S.; Matthews, G. F.; Mayer, M.; Petersson, P.; Contributors, Jet

doi:10.1088/0031-8949/t167/1/014075

Cited by 58 publications

(69 citation statements)

References 18 publications

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“…This thickness is typically in the same order of magnitude as that of the supersaturated layer found in tokamak deposits [12]. In our spectra, we have identified defect induced bands that are due to the selection rule relaxation caused by these defects, leading to the observation of the PDOS and 2PDOS…”

Section: Summary/discussionmentioning

confidence: 55%

“…In that framework, the surface composition and morphology modifications under operation will lead to changes in the material properties, some of them related to safety issues; these changes will have to be measured and understood. The lifetime of these PFCs and their fuel retention properties will be influenced by the migration [8] and/or melting of elements in the machine [9,10], the production of dust, the hydrogen isotope retention [11,12], the complex surface erosion mechanisms, and the impurity contamination (traces of carbon and/or oxygen, nitrogen seeding [13],...) leading to formation of new mixed materials/phases. Surface characterisation techniques are then necessary to measure the elemental changes in JET and in ITER.…”

Section: Introductionmentioning

confidence: 99%

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Preparing the future post-mortem analysis of beryllium-based JET and ITER samples by multi-wavelengths Raman spectroscopy on implanted Be, and co-deposited Be

et al. 2017

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This study demonstrates that Raman microscopy is a suitable technique for future post mortem analyses of JET and ITER plasma facing components. We focus here on laboratory deposited and bombarded samples of beryllium and beryllium carbides and start to build a reference spectral databases for fusion relevant beryllium-based materials. We identified the beryllium phonon density of states, its second harmonic and E 2G and B 2G second harmonic and combination modes for defective beryllium in the spectral range 300-700 and 700-1300 cm -1 , lying close to Be-D modes of beryllium hydrides. We also identified beryllium carbide signature, Be 2 C, combining Raman microscopy and DFT calculation. We have shown that, depending on the optical constants of the material probed, in depth sensitivity at the nanometer scale can be performed using different wavelengths. This way, we demonstrate that multi-wavelength Raman microscopy is sensitive to in-depth stress caused by ion implantation (down to ≈30 nm under the surface for Be) and Be/C concentration (down to 400 nm or more under the surface for Be+C), which is a main contribution of this work. The depth resolution reached can then be adapted for studying the supersaturated surface layer found on tokamak deposits.2

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Section: Summary/discussionmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Preparing the future post-mortem analysis of beryllium-based JET and ITER samples by multi-wavelengths Raman spectroscopy on implanted Be, and co-deposited Be

et al. 2017

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“…It has been shown in earlier studies of the limiter and divertor tiles from JET-ILW that-as expected-the surfaces contain a mix co-deposited species: fuel atoms, beryllium, carbon, nitrogen and metals [35][36][37][38][39]. However, no information on the chemical form has been given, while the point should not be neglected in the environment containing both Be and W which are known to form binary mixed materials of low melting point [40].…”

Section: Intermetallic Compounds On Pfsmentioning

confidence: 89%

Fuel inventory and deposition in castellated structures in JET-ILW

et al. 2017

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Since 2011 the JET tokamak has been operated with a metal ITER-like wall (JET-ILW) including castellated beryllium limiters and lamellae-type bulk tungsten tiles in the divertor. This has allowed for a large scale test of castellated plasma-facing components (PFC). Procedures for sectioning the limiters into single blocks of castellation have been developed. This facilitated morphology studies of morphology of surfaces inside the grooves for limiters after experimental campaigns 2011-2012 and 2013-2014. The deposition in the 0.4-0.5 mm wide grooves of the castellation is 'shallow'. It reaches 1-2 mm into the 12 mm deep gap. Deuterium concentrations are small (mostly below 1 × 10 18 cm −2). The estimated total amount of deuterium in all the castellated limiters does not exceed the inventory of the plasma-facing surfaces (PFS) of the limiters. There are only traces of Ni, Cr and Fe deposited in the castellation gaps. The same applies to the carbon content. Also low deposition of D, Be and C has been measured on the sides of the bulk tungsten lamellae pieces. Modelling clearly reflects: (a) a sharp decrease in the measured deposition profiles and (b) an increase in deposition with the gap width. Both experimental and modelling data give a strong indication and information to ITER that narrow gaps in the castellated PFC are essential. X-ray diffraction on PFS has clearly shown two distinct composition patterns: Be with an admixture of Be-W intermetallic compounds (e.g. Be 22 W) in the deposition zone, whilst only pure Be has been detected in the erosion zone. The lack of compound formation in the erosion zone indicates that no distinct changes in the thermo-mechanical properties of the Be PFC might be expected.

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“…Nuclear reaction analysis (NRA) with incident 3 He ions at energies from 0.8 to 4.5 MeV was applied at a reaction angle of 135° to measure the amounts of D, Be and C. The D content was measured using the D ( 3 He,p) 4 He reaction [17], the 9 Be( 3 He,p 0 ) 11 B and 9 Be( 3 He,p 1 ) 11 B reactions were used for measuring the Be content.The 12 C( 3 He,p 0 ) 14 N reaction was used to determine the amount of 12 C. In order to take overlap with protons from the 9 Be( 3 He,p 3 ) 11 B reaction into account the number of protons from this reaction was simulated using cross-section data from [18] and subtracted from the 12 C( 3 He,p 0 ) 14 N peak. For very thin layers protons from the 12 C( 3 He,p 1 ) 14 N reaction were also used to determine the amount of 12 C, in that case overlap with 9 Be( 3 He,p 6 ) 11 B and 9 Be( 3 He,p 7 ) 11 B peaks was checked using cross-section data from [19].…”

Section: Methodsmentioning

confidence: 99%

“…During the first operational campaign of JET with the ITER-like wall (ILW -1) in the years 2011-2012 profound changes of the material erosion/deposition pattern in the divertor were observed, as compared to the previous operation of JET with all carbon walls: The total mass of deposited material decreased by a factor of 4-9 [5], and the deuterium retention inside the JET vessel decreased by a factor of 10 to 20 [12]. These results are highly promising for the extrapolated tritium retention in ITER.…”

Section: Introductionmentioning

confidence: 99%

Erosion and deposition in the JET divertor during the second ITER-like wall campaign

et al. 2017

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Erosion of plasma-facing materials and successive transport and redeposition of eroded material are crucial processes determining the lifetime of plasma-facing components and the trapped tritium inventory in redeposited material layers. Erosion and deposition in the JET divertor were studied during the second JET ITER-like wall campaign ILW-2 in 2013-2014 by using a poloidal row of specially prepared divertor marker tiles including the tungsten bulk tile 5. The marker tiles were analysed using elastic backscattering with 3 to 4.5 MeV incident protons and nuclear reaction analysis using 0.8 to 4.5 MeV 3 He ions before and after the campaign. The erosion/deposition pattern observed during ILW-2 is qualitatively comparable to the first campaign ILW-1 in 2011-2012: Deposits consist mainly of beryllium with 5-20 at.% of carbon and oxygen and small amounts of Ni and W. The highest deposition with deposited layer thicknesses up to 30 μm per campaign is still observed on the upper and horizontal parts of the inner divertor. Outer divertor tiles 5, 6, 7 and 8 are net W erosion areas. The observed D inventory is roughly comparable to the inventory observed during ILW-1. The results obtained during

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Long-term fuel retention in JET ITER-like wall

Cited by 58 publications

References 18 publications

Preparing the future post-mortem analysis of beryllium-based JET and ITER samples by multi-wavelengths Raman spectroscopy on implanted Be, and co-deposited Be

Preparing the future post-mortem analysis of beryllium-based JET and ITER samples by multi-wavelengths Raman spectroscopy on implanted Be, and co-deposited Be

Fuel inventory and deposition in castellated structures in JET-ILW

Erosion and deposition in the JET divertor during the second ITER-like wall campaign

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