TEM investigation of the influence of dose rate on radiation damage and deuterium retention in tungsten

Chromiński, Witold; Ciupiński, Ł.; Bazarnik, Piotr; Markelj, S.; Schwarz-Selinger, T.

doi:10.1016/j.matchar.2019.05.028

Cited by 14 publications

(11 citation statements)

References 21 publications

(26 reference statements)

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“…Stitched TEM images of these specimens can be found in the supplementary material (figures S5 and S6). The measured average dislocation densities (in the grain interior) are again almost the same in both materials: (2.2 ± 0.3) × 10 14 m −2 in the sample strained to 36% at 573 K and (2.1 ± 0.3) × 10 14 m −2 in the sample strained to 38% at 873 K. These dislocation densities are comparable with that in as-received hot-rolled W of (3.2 ± 1.7) × 10 14 m −2 [5], as well as with that in recrystallized W irradiated by 20 MeV W ions to 0.23 dpa [39]. Note that Manhard et al [5] counted not only dislocations in the grain interior (like in the present work), but also dislocation agglomerations near grain boundaries and dislocation walls.…”

Section: Microstructure Evolutionsupporting

confidence: 63%

“…Note that the sample temperatures during the plasma exposures used in the present study (370 K and 450 K) are below the operation temperature of most of the W components in ITER (the minimum temperature is determined by the cooling water inlet temperature of 343 K) [1,2]. Recently Chrominski et al [39] observed that, despite the different character and density of dislocations (lines and loops) observed in radiation-damaged W irradiated with different dose rates (to the same damage level), the D retention in the samples was essentially the same already at 295 K. It was concluded that radiation-induced dislocations play a little role in D retention in W. Hence, at material temperatures relevant for ITER and DEMO trapping at dislocations can be expected to yield a small contrib ution to H isotope retention in W.…”

Section: Discussionmentioning

confidence: 79%

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Deuterium trapping by deformation-induced defects in tungsten

et al. 2019

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The influence of defects induced by plastic deformation of tungsten (W) on deuterium (D) retention has been studied. Recrystallized W samples were subjected to tensile deformations at temperatures of 573 K and 873 K to strains in the range of 3-38 %. The dislocation density measured by transmission electron microscopy (TEM) increased by about 40 times after deformation to the highest strain. The introduced defects were decorated with D by exposure to a low-flux D plasma at sample temperatures of 370 K and 450 K. D retention in the samples was studied using nuclear reaction analysis (NRA) and thermal desorption spectroscopy (TDS). The trapped D concentrations after the plasma exposures were low (up to a few times 10 −4 at. fr.) and increased more slowly with strain than the dislocation density. Small vacancy-like defects and large vacancy clusters were detected in the samples by positron annihilation lifetime spectroscopy (PALS). Their concentrations also increased with strain more weakly than the dislocation density. It was concluded that these defects governed the D retention under plasma exposure at 450 K, while dislocations gave only a small contribution. It was also found that deformation already to the lowest strains significantly facilitates the formation of blister-like structures under D plasma exposure at 370 K. The defects associated with blister-like structures presumably gave a substantial contribution to D retention at 370 K.

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Section: Microstructure Evolutionsupporting

confidence: 63%

Section: Discussionmentioning

confidence: 79%

Deuterium trapping by deformation-induced defects in tungsten

et al. 2019

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“…They have found detrapping energies ranging from 0.8 -1.2 eV for various dislocation structures, number of trapped HIs and for various number of trapped self-interstitial W atoms. Although some of these de-trapping energies are in line with our defect type II fill-level de-trapping energies the typical dislocation areal density found in such samples by TEM analysis [27,53] is around 10 14 m -2 . This is equivalent to a volumetric concentration of 10 -4 at.%.…”

Section: 2 Defect Type IIsupporting

confidence: 87%

New rate equation model to describe the stabilization of displacement damage by hydrogen atoms during ion irradiation in tungsten

et al. 2020

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The effect of deuterium (D) presence on the amount of displacement damage created in tungsten (W) during high-energy W-ion irradiation is investigated. For this purpose, we have performed modelling of experimental results where W was sequentially or simultaneously irradiated by 10.8 MeV W ions and exposed to 300 eV D ions. A novel displacement damage creation and stabilization model was newly developed and introduced into the MHIMS-Reservoir (Migration of Hydrogen Isotopes in MaterialS) code. It employs macroscopic rate equations (MREs) for solving the evolution of solute and trapped D concentrations in the material. The new displacement damage creation and stabilization model is based on spontaneous recombination of Frenkel pairs and stabilization of defects that are occupied by D atoms. By using the new model, we could successfully replicate the measured D depth profiles and D thermal desorption data, where a higher defect concentration was observed when D was present during W irradiation as compared to when no D was present. For this we utilized parameters, which include the number of distinct defect types, the de-trapping energies of their fill-levels, their saturation concentrations and their probability for stabilization if they contain a D during the W-ion irradiation. To successfully replicate the experimental results three distinct defect types were needed with several fill-levels. By comparing the de-trapping energies of the defect filllevels with data available from the literature, the defect types were identified as single-vacancies, small vacancy clusters and large vacancy clusters. The effect of D presence was found to be largest in single vacancies as its concentration increased by about a factor of three, while the concentration of small vacancy clusters increased by about a factor of two. Large vacancy clusters were found to be largely unaffected as they showed very little increase in concentration when D was present.

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“…However, this is unlikely as because most of the SIA atoms are lost to various free surfaces such as grain boundaries very quickly after the process of W irradiation because of their high mobility [45]- [48]. In samples which were treated in a manner similar to ours, the volumetric density of dislocations has been measured to be approximately 10 -4 at.% [9], [49]. Assuming all of the dislocations measured are of the SIA type, the measured density of dislocations provides an upper limit on the density of all SIAs that are available during our annealing process.…”

Section: Mechanisms Of Displacement Damage Evolutionmentioning

confidence: 59%

Effect of D on the evolution of radiation damage in W during high temperature annealing

et al. 2020

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The effect of deuterium (D) on the annealing of radiation damage was studied. Tungsten (W) samples were sequentially irradiated with 20 MeV W ions at room temperature and loaded with a low-temperature D plasma at 370 K to decorate the created defects. After this, half of each sample was W irradiated at room temperature again to create additional radiation damage. To study the evolution of the created defects with D being present, samples were annealed by heating them to a desired temperature and held for two hours. The surviving displacement damage was decorated by re-exposing the samples to the same D plasma as before. At various steps of the experiment the D depth profiles were measured using Nuclear Reaction Analysis and after the last re-exposure a Thermal Desorption Spectroscopy analysis was done to determine the D desorption spectra.D release is dominated by two desorption peaks centered at 520 K and 780 K for a 3 K/min temperature ramp. For temperature holds below 500 K no measurable change in the intensity of the desorption peaks was measured. For temperature holds above 500 K, the low temperature D desorption peak started to reduce in intensity. The high temperature D desorption peak showed signs of evolution only for temperature holds above 600 K. This behaviour was independent of the number of W irradiations used.A macroscopic rate equation model was used to recreate the experimental results. Using the fill-level dependant D-defect interaction picture we were able to determine that three distinct defect types with several fill-levels each are sufficient to describe the results. The concentrations of defect 1 (vacancies) and defect 2 (small vacancy clusters) reduced by 50 % and 35 %, respectively, after an 800 K temperature hold. No reduction was found for defect 3 (large vacancy clusters).

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TEM investigation of the influence of dose rate on radiation damage and deuterium retention in tungsten

Cited by 14 publications

References 21 publications

Deuterium trapping by deformation-induced defects in tungsten

Deuterium trapping by deformation-induced defects in tungsten

New rate equation model to describe the stabilization of displacement damage by hydrogen atoms during ion irradiation in tungsten

Effect of D on the evolution of radiation damage in W during high temperature annealing

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