Pub Date : 2025-10-08DOI: 10.1016/j.nme.2025.101999
E.A. Hodille , D. Piccinelli , M. Bertoglio , T. Loarer , J. Dufour , J. Denis , E. Lascar , G. Ciraolo , P. Tamain , Y. Ferro , E. Geulin , A. Gallo , P. Moreau , S. Vartanian , R. Bisson , B. Pégourié , Y. Anquetin , J. Gaspar , Y. Corre , K. Dunnell , T. Wauters
A fuelling changeover experiment from Deuterium (D) to Hydrogen (H), and back has been performed in WEST to study the retention and removal in metallic devices with actively cooled ITER-grade tungsten divertor. The present study reports trapping-diffusion modelling of H and D in the W divertor during this session. In this model approach, the divertor is represented by multiple (radially distributed) 1D simulations. The plasma exposure conditions are calculated with soledge3x-eirene, delivering the heat and particle flux for each of the divertor bins. The material model is parametrized by reproducing a thermal desorption spectrometry experiment and an isotope exchange experiment on polycristalline tungsten. The simulated outgassing flux during the post-pulse phase of the changeover pulses are converted to H, HD and D partial pressure in the WEST vacuum vessel. The calculated pressure is one order of magnitude below the experimental one as only the contribution from the divertor is taken into account in this analysis. An additional source of H outgassing should be taken into account to recover the dynamics of the H partial pressure, especially during D plasma phases. However, the dynamics of HD and D pressure drop is similar in the simulations and experiments. Finally, the analysis of the divertor H/D inventory shows that the isotope exchange is efficient near the plasma exposed surface but is limited by the D/H migration towards the bulk.
{"title":"Modelling fuel retention in the W divertor during the D/H/D changeover experiment in WEST","authors":"E.A. Hodille , D. Piccinelli , M. Bertoglio , T. Loarer , J. Dufour , J. Denis , E. Lascar , G. Ciraolo , P. Tamain , Y. Ferro , E. Geulin , A. Gallo , P. Moreau , S. Vartanian , R. Bisson , B. Pégourié , Y. Anquetin , J. Gaspar , Y. Corre , K. Dunnell , T. Wauters","doi":"10.1016/j.nme.2025.101999","DOIUrl":"10.1016/j.nme.2025.101999","url":null,"abstract":"<div><div>A fuelling changeover experiment from Deuterium (D) to Hydrogen (H), and back has been performed in WEST to study the retention and removal in metallic devices with actively cooled ITER-grade tungsten divertor. The present study reports trapping-diffusion modelling of H and D in the W divertor during this session. In this model approach, the divertor is represented by multiple (radially distributed) 1D simulations. The plasma exposure conditions are calculated with <span>soledge3x-eirene</span>, delivering the heat and particle flux for each of the divertor bins. The material model is parametrized by reproducing a thermal desorption spectrometry experiment and an isotope exchange experiment on polycristalline tungsten. The simulated outgassing flux during the post-pulse phase of the changeover pulses are converted to H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>, HD and D<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> partial pressure in the WEST vacuum vessel. The calculated pressure is one order of magnitude below the experimental one as only the contribution from the divertor is taken into account in this analysis. An additional source of H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> outgassing should be taken into account to recover the dynamics of the H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> partial pressure, especially during D plasma phases. However, the dynamics of HD and D<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> pressure drop is similar in the simulations and experiments. Finally, the analysis of the divertor H/D inventory shows that the isotope exchange is efficient near the plasma exposed surface but is limited by the D/H migration towards the bulk.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101999"},"PeriodicalIF":2.7,"publicationDate":"2025-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-05DOI: 10.1016/j.nme.2025.101993
Margherita Sardo , Samuli Heikkinen , Jose Pacheco , Marta Freitas , Nuno A. Marques , Sergio A. Reis , Mónica Mendes Reis
ITER EU First Wall Panels (FWPs) contain CuCrZr-IG (ITER grade) as heat sink material, which is also subject to thermo-mechanical loads during operation. Hence, in addition to thermal properties requirements, there is certain level of mechanical properties required from the material, The precipitation-hardening CuCrZr-IG alloy requires a solution annealing heat treatment with rapid cooling followed by ageing treatment to achieve the desired mechanical properties. In the past, a minimum cooling rate of 60 °C/min after solution annealing was demonstrated to ensure the proper precipitation hardening. Due to the large FWP size and dimension accuracy, gas cooling was chosen to avoid the large deformations and oxidation that quenching in water or oil would cause. The effectiveness of the treatment depends mostly on the part’s mass, type of gas used and furnace characteristics. A cooling rate of 60 °C/min proved difficult to achieve using nitrogen because of FWP mass (around 1.5 tons), while the use of other gases (e.g. helium) is not economically viable for large-scale FWP series manufacturing.
The cooling rate study is performed on samples of CuCrZr-IG to simulate the conditions the material will experience when incorporated into a full-scale panel. After solution annealing, different cooling rates (20 °C/min, 30 °C/min, 40 °C/min, 50 °C/min, 60 °C/min) were tested to study mechanical and physical properties of CuCrZr-IG alloy, to see whether the slower cooling rate could be applied on full scale FWPs. The experimental results have shown that cooling rates, slower than 60 °C/min, do not have a substantial detrimental effect on material strength, when all heat cycles that correspond to FWP manufacturing route are applied. Material subject to slower cooling rates have shown compliance with HIP manufacturing process requirements, in most cases.
The test results include yield strength, ultimate strength, elongation, grain size and hardness. Although there are no specific requirements regarding the hardness of the material, this property may serve as a future resource to assess material properties without the need for destructive testing on full-scale FWPs.
CuCrZr-IG from two suppliers was tested. The effect of different cooling rates has proven to be similar on the two suppliers’ materials, even though one supplier shows values consistently above the other, in absolute terms.
ITER EU First Wall Panels （FWPs）包含CuCrZr-IG （ITER级）作为散热材料，在运行过程中也会受到热机械负荷的影响。因此，除了热性能要求外，还要求材料具有一定的机械性能。沉淀硬化CuCrZr-IG合金需要进行快速冷却的固溶退火热处理，然后进行时效处理，以达到所需的机械性能。过去的研究表明，溶液退火后的最小冷却速度为60°C/min，以确保适当的沉淀硬化。由于FWP尺寸大，尺寸精度高，因此选用气冷，避免了在水或油中淬火时产生的大变形和氧化。处理的有效性主要取决于零件的质量，所用气体的类型和炉子的特性。由于FWP的质量（约1.5吨），使用氮气很难达到60°C/min的冷却速度，而使用其他气体（例如氦气）对于大规模的FWP系列制造在经济上是不可行的。冷却速率研究是在CuCrZr-IG样品上进行的，以模拟材料在纳入全尺寸面板时所经历的条件。溶液退火后，采用不同的冷却速率（20°C/min、30°C/min、40°C/min、50°C/min、60°C/min）对CuCrZr-IG合金的力学和物理性能进行了研究，以确定较慢的冷却速率是否适用于全尺寸FWPs。实验结果表明，当采用与FWP制造路线相对应的所有热循环时，低于60°C/min的冷却速率对材料强度没有实质性的有害影响。在大多数情况下，冷却速度较慢的材料符合HIP制造工艺要求。试验结果包括屈服强度、极限强度、伸长率、晶粒尺寸和硬度。虽然对材料的硬度没有具体的要求，但这种性能可以作为未来评估材料性能的资源，而不需要在全尺寸的FWPs上进行破坏性测试。对两家供应商的CuCrZr-IG进行了测试。不同冷却速率对两个供应商的材料的影响已被证明是相似的，即使一个供应商的绝对值始终高于另一个供应商。
{"title":"ITER EU first wall panel CuCrZr cooling rate study","authors":"Margherita Sardo , Samuli Heikkinen , Jose Pacheco , Marta Freitas , Nuno A. Marques , Sergio A. Reis , Mónica Mendes Reis","doi":"10.1016/j.nme.2025.101993","DOIUrl":"10.1016/j.nme.2025.101993","url":null,"abstract":"<div><div>ITER EU First Wall Panels (FWPs) contain CuCrZr-IG (ITER grade) as heat sink material, which is also subject to thermo-mechanical loads during operation. Hence, in addition to thermal properties requirements, there is certain level of mechanical properties required from the material, The precipitation-hardening CuCrZr-IG alloy requires a solution annealing heat treatment with rapid cooling followed by ageing treatment to achieve the desired mechanical properties. In the past, a minimum cooling rate of 60 °C/min after solution annealing was demonstrated to ensure the proper precipitation hardening. Due to the large FWP size and dimension accuracy, gas cooling was chosen to avoid the large deformations and oxidation that quenching in water or oil would cause. The effectiveness of the treatment depends mostly on the part’s mass, type of gas used and furnace characteristics. A cooling rate of 60 °C/min proved difficult to achieve using nitrogen because of FWP mass (around 1.5 tons), while the use of other gases (e.g. helium) is not economically viable for large-scale FWP series manufacturing.</div><div>The cooling rate study is performed on samples of CuCrZr-IG to simulate the conditions the material will experience when incorporated into a full-scale panel. After solution annealing, different cooling rates (20 °C/min, 30 °C/min, 40 °C/min, 50 °C/min, 60 °C/min) were tested to study mechanical and physical properties of CuCrZr-IG alloy, to see whether the slower cooling rate could be applied on full scale FWPs. The experimental results have shown that cooling rates, slower than 60 °C/min, do not have a substantial detrimental effect on material strength, when all heat cycles that correspond to FWP manufacturing route are applied. Material subject to slower cooling rates have shown compliance with HIP manufacturing process requirements, in most cases.</div><div>The test results include yield strength, ultimate strength, elongation, grain size and hardness. Although there are no specific requirements regarding the hardness of the material, this property may serve as a future resource to assess material properties without the need for destructive testing on full-scale FWPs.</div><div>CuCrZr-IG from two suppliers was tested. The effect of different cooling rates has proven to be similar on the two suppliers’ materials, even though one supplier shows values consistently above the other, in absolute terms.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101993"},"PeriodicalIF":2.7,"publicationDate":"2025-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-02DOI: 10.1016/j.nme.2025.101998
A. Hakola , J. Likonen , T. Vuoriheimo , E. Grigore , I. Jõgi , P. Paris , A. Lagoyannis , K. Mergia , P. Tsavalas , E. Fortuna-Zaleśna , M. Balden , E. Bernard , M. Diez , E. Tsitrone , the WEST team
We discuss detailed elemental, compositional, and structural properties of co-deposited layers formed on the special marker tiles at the divertor region of the WEST tokamak during its Phase 1 (2016–2021) plasma operations. The main new aspects are applying high depth and mass resolution, provided by a combination of state-of-the-art local analysis techniques, throughout the entire surface deposit and cross correlating the obtained results with published ones. We also show that proper comparison of the different data sets requires deconvoluting them with several experimental parameters, most importantly the lateral and depth resolutions as well as the analysis volume. The analyses reveal that the thickest deposits are formed towards the end of Phase 1, and the change is particularly noticeable after the C4 campaign with the longest exposure time and the largest number of boronizations carried out. Thin deposits (thickness up to 1–2 μm) are found on several poloidal regions of the analysed tiles, and they exhibit a clear sandwich-type of structure consisting of distinct B, C, O, and/or W-rich sublayers together with metallic impurities. Close to the inner strike point, thick deposits are measured (thickness several tens of micrometres) and they show complex, stratified structures, however, the same sublayer structure as for the thin deposits can still be recognized. On the thin deposits, the very surface is rich in B while for the thick deposits W dominates the topmost surface layers in the latter stages of Phase 1. For all the analysed samples, the superficial B and W concentrations are on average 10–30 at.% in addition to which high oxygen levels up to 15–40 at.% are measured. In the erosion-dominated regions, deposits can be observed but only in the microscopic scale inside recessed valleys, up to thicknesses of several micrometres. A dynamical erosion–deposition picture for the surface layers is confirmed, further contributing to their structure and composition.
{"title":"Evolution of elemental depth profiles on co-deposited layers at the divertor region of the WEST tokamak during its Phase 1 operations","authors":"A. Hakola , J. Likonen , T. Vuoriheimo , E. Grigore , I. Jõgi , P. Paris , A. Lagoyannis , K. Mergia , P. Tsavalas , E. Fortuna-Zaleśna , M. Balden , E. Bernard , M. Diez , E. Tsitrone , the WEST team","doi":"10.1016/j.nme.2025.101998","DOIUrl":"10.1016/j.nme.2025.101998","url":null,"abstract":"<div><div>We discuss detailed elemental, compositional, and structural properties of co-deposited layers formed on the special marker tiles at the divertor region of the WEST tokamak during its Phase 1 (2016–2021) plasma operations. The main new aspects are applying high depth and mass resolution, provided by a combination of state-of-the-art local analysis techniques, throughout the entire surface deposit and cross correlating the obtained results with published ones. We also show that proper comparison of the different data sets requires deconvoluting them with several experimental parameters, most importantly the lateral and depth resolutions as well as the analysis volume. The analyses reveal that the thickest deposits are formed towards the end of Phase 1, and the change is particularly noticeable after the C4 campaign with the longest exposure time and the largest number of boronizations carried out. Thin deposits (thickness up to 1–2 μm) are found on several poloidal regions of the analysed tiles, and they exhibit a clear sandwich-type of structure consisting of distinct B, C, O, and/or W-rich sublayers together with metallic impurities. Close to the inner strike point, thick deposits are measured (thickness several tens of micrometres) and they show complex, stratified structures, however, the same sublayer structure as for the thin deposits can still be recognized. On the thin deposits, the very surface is rich in B while for the thick deposits W dominates the topmost surface layers in the latter stages of Phase 1. For all the analysed samples, the superficial B and W concentrations are on average 10–30 at.% in addition to which high oxygen levels up to 15–40 at.% are measured. In the erosion-dominated regions, deposits can be observed but only in the microscopic scale inside recessed valleys, up to thicknesses of several micrometres. A dynamical erosion–deposition picture for the surface layers is confirmed, further contributing to their structure and composition.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101998"},"PeriodicalIF":2.7,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-30DOI: 10.1016/j.nme.2025.101995
Jiaguan Peng , Jiayin Li , Mengqi Zhang , Fengning Liu , Xiuli Zhu , Shin Kajita , Qiannan Yu , Tiangang Zhang , Long Cheng , Sijie Hao , Yue Yuan , Guang-Hong Lu
Helium has been shown to effectively retard recrystallization and grain growth in tungsten for fusion application. However, it is unclear how hydrogen isotopes affect recrystallization, as their desorption temperature is far lower than the recrystallization temperature in tungsten, preventing them from remaining in the material and taking effect. Using rolled copper, this study investigated the effects of deuterium and helium plasma on recrystallization by leveraging the high deuterium desorption temperature in copper. Rolled copper samples exposed to deuterium or helium plasma were annealed at temperatures from 300 to 800℃. It was found that deuterium plasma exposure led to a slight retardation of the recrystallization but no impact on the grain growth. Helium plasma exposure promoted recrystallization but significantly inhibited grain growth, which is different from the effect in tungsten. This work offers preliminary insights into understanding the degradation of mechanical properties in copper-based materials with hydrogen isotopes and helium under high-temperature conditions for fusion applications.
{"title":"Effect of deuterium and helium plasma exposure on recrystallization in copper","authors":"Jiaguan Peng , Jiayin Li , Mengqi Zhang , Fengning Liu , Xiuli Zhu , Shin Kajita , Qiannan Yu , Tiangang Zhang , Long Cheng , Sijie Hao , Yue Yuan , Guang-Hong Lu","doi":"10.1016/j.nme.2025.101995","DOIUrl":"10.1016/j.nme.2025.101995","url":null,"abstract":"<div><div>Helium has been shown to effectively retard recrystallization and grain growth in tungsten for fusion application. However, it is unclear how hydrogen isotopes affect recrystallization, as their desorption temperature is far lower than the recrystallization temperature in tungsten, preventing them from remaining in the material and taking effect. Using rolled copper, this study investigated the effects of deuterium and helium plasma on recrystallization by leveraging the high deuterium desorption temperature in copper. Rolled copper samples exposed to deuterium or helium plasma were annealed at temperatures from 300 to 800℃. It was found that deuterium plasma exposure led to a slight retardation of the recrystallization but no impact on the grain growth. Helium plasma exposure promoted recrystallization but significantly inhibited grain growth, which is different from the effect in tungsten. This work offers preliminary insights into understanding the degradation of mechanical properties in copper-based materials with hydrogen isotopes and helium under high-temperature conditions for fusion applications.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101995"},"PeriodicalIF":2.7,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145268928","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-29DOI: 10.1016/j.nme.2025.101997
Baoping Gong, Hao Cheng, Juemin Yan, Long Wang, Qixiang Cao, Long Zhang, Jiming Chen, Yongjin Feng
Packing density of the tritium breeder pebble beds are closely related to the effective density of the lithium atom in the breeding cavities. And the higher the density of lithium atoms the higher the tritium breeding ratio. Therefore, in this work, the effect of vibration parameters on the densification behavior of tritium breeder pebble beds were investigated by Discrete element method (DEM) simulation. The findings indicate that vertical vibration can substantially enhance the densification of the mono-sized pebble bed. The average packing factor of the vibrated bed attains it’s maximum when the periodic boundary is employed. As the vibration frequency and amplitude increase, the average packing factor of the pebble bed experiences an initial rise, followed by a subsequent decrease. The effect of vibration intensity displays a similar pattern. Furthermore, as the vibration time is extended, the average packing factor of the pebble bed undergoes a gradual increase, ultimately reaching 0.6409 when the vibration time extends 200 s. The state is distinguished by the random close packing of mono-sized pebble beds. The findings presented in this paper contribute to the optimization of the fabrication and assembly process of solid blanket for fusion reactors.
{"title":"Densification behavior of ceramic tritium breeder pebble beds under vertical vibration: Effect of vibration parameters","authors":"Baoping Gong, Hao Cheng, Juemin Yan, Long Wang, Qixiang Cao, Long Zhang, Jiming Chen, Yongjin Feng","doi":"10.1016/j.nme.2025.101997","DOIUrl":"10.1016/j.nme.2025.101997","url":null,"abstract":"<div><div>Packing density of the tritium breeder pebble beds are closely related to the effective density of the lithium atom in the breeding cavities. And the higher the density of lithium atoms the higher the tritium breeding ratio. Therefore, in this work, the effect of vibration parameters on the densification behavior of tritium breeder pebble beds were investigated by Discrete element method (DEM) simulation. The findings indicate that vertical vibration can substantially enhance the densification of the mono-sized pebble bed. The average packing factor of the vibrated bed attains it’s maximum when the periodic boundary is employed. As the vibration frequency and amplitude increase, the average packing factor of the pebble bed experiences an initial rise, followed by a subsequent decrease. The effect of vibration intensity displays a similar pattern. Furthermore, as the vibration time is extended, the average packing factor of the pebble bed undergoes a gradual increase, ultimately reaching 0.6409 when the vibration time extends 200 s. The state is distinguished by the random close packing of mono-sized pebble beds. The findings presented in this paper contribute to the optimization of the fabrication and assembly process of solid blanket for fusion reactors.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101997"},"PeriodicalIF":2.7,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-28DOI: 10.1016/j.nme.2025.101996
E. Pitthan , M. Fellinger , B.Burazor Domazet , P.M. Wolf , J. Shams-Latifi , F. Aumayr , D. Primetzhofer
This work investigates how corrections to fundamental parameters describing ion–solid interaction affect sputtering yield simulations based on the binary collision approximation. We review recent experimental assessments of electronic stopping power and short-range repulsive interatomic potentials for light plasma species (H, D, He) in plasma-facing material candidates (W, Fe, EUROFER97), and compare them to widely used semi-empirical and theoretical models. At low energies, discrepancies of up to 60% relative to SRIM-2013 and up to 210% relative to SRIM-1997 are identified for the specific energy loss, highlighting the need for improved input parameters. We assess the sensitivity of sputtering yields to these corrections using SDTrimSP simulations, and compare the results to new experimental sputter yield data obtained for re-deposited thin W, Fe, and EUROFER97 films on a high-sensitivity quartz crystal microbalance. Incorporating derived stopping powers and interatomic potentials into the simulation significantly reduces the discrepancies between experimental and simulated sputtering yields. Remaining uncertainties and model limitations, such as crystal structure effects and ion implantation, are discussed.
{"title":"Interaction of light ions with plasma-facing materials: Improved experimental accuracy and its impact on sputter yield simulations","authors":"E. Pitthan , M. Fellinger , B.Burazor Domazet , P.M. Wolf , J. Shams-Latifi , F. Aumayr , D. Primetzhofer","doi":"10.1016/j.nme.2025.101996","DOIUrl":"10.1016/j.nme.2025.101996","url":null,"abstract":"<div><div>This work investigates how corrections to fundamental parameters describing ion–solid interaction affect sputtering yield simulations based on the binary collision approximation. We review recent experimental assessments of electronic stopping power and short-range repulsive interatomic potentials for light plasma species (H, D, He) in plasma-facing material candidates (W, Fe, EUROFER97), and compare them to widely used semi-empirical and theoretical models. At low energies, discrepancies of up to 60% relative to SRIM-2013 and up to 210% relative to SRIM-1997 are identified for the specific energy loss, highlighting the need for improved input parameters. We assess the sensitivity of sputtering yields to these corrections using SDTrimSP simulations, and compare the results to new experimental sputter yield data obtained for re-deposited thin W, Fe, and EUROFER97 films on a high-sensitivity quartz crystal microbalance. Incorporating derived stopping powers and interatomic potentials into the simulation significantly reduces the discrepancies between experimental and simulated sputtering yields. Remaining uncertainties and model limitations, such as crystal structure effects and ion implantation, are discussed.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101996"},"PeriodicalIF":2.7,"publicationDate":"2025-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-27DOI: 10.1016/j.nme.2025.101994
S.J. Shetty , M. Veis , D. Sokulski , P. Gąsior , P. Veis
Laser Induced Breakdown Spectroscopy (LIBS) is often referred to as an in-situ and rapid analysis technique. Although the experimental setup is relatively simple, the quantification of elements in a sample containing multiple elements poses challenges for faster and reliable quantification. The application of machine learning (ML) techniques is one of the optimal solutions to achieve the quantified result in real-time. This study investigates the performance of Deep Neural Network (DNN), Gated Recurrent Unit (GRU), and Bidirectional Long Short-Term Memory (Bi-LSTM) models in analyzing the composition of first wall materials of thermonuclear reactors. The dataset was modelled based on 7400 simulated spectra at a resolution of 4000, each row comprising 41,730 data points. Initial evaluations revealed that GRU and Bi-LSTM models outperformed DNN in capturing spectral data relationships, as indicated by higher R2 scores and lower Mean Squared Error (MSE). To mitigate computational complexity and eliminate redundant data, a bottleneck approach was used, which reduced the feature space to 1024 while enhancing predictive performance. Further enhancements were achieved through hyperparameter tuning using Polar Bear Optimizer (PBO), leading to significant improvements in the overall model accuracy. The integration of dimensionality reduction and hyperparameter optimization techniques demonstrated significant enhancement in the predictive capabilities of Recurrent Neural Network (RNN) models. This study emphasizes the potential of machine learning techniques in addressing the challenges associated with the rapid quantification of elements in complex fusion related samples.
{"title":"Evaluation of DNN and RNN for the determination of the chemical composition of dimensionality-reduced LIBS spectra of fusion-based materials","authors":"S.J. Shetty , M. Veis , D. Sokulski , P. Gąsior , P. Veis","doi":"10.1016/j.nme.2025.101994","DOIUrl":"10.1016/j.nme.2025.101994","url":null,"abstract":"<div><div>Laser Induced Breakdown Spectroscopy (LIBS) is often referred to as an in-situ and rapid analysis technique. Although the experimental setup is relatively simple, the quantification of elements in a sample containing multiple elements poses challenges for faster and reliable quantification. The application of machine learning (ML) techniques is one of the optimal solutions to achieve the quantified result in real-time. This study investigates the performance of Deep Neural Network (DNN), Gated Recurrent Unit (GRU), and Bidirectional Long Short-Term Memory (Bi-LSTM) models in analyzing the composition of first wall materials of thermonuclear reactors. The dataset was modelled based on 7400 simulated spectra at a resolution of 4000, each row comprising 41,730 data points. Initial evaluations revealed that GRU and Bi-LSTM models outperformed DNN in capturing spectral data relationships, as indicated by higher R<sup>2</sup> scores and lower Mean Squared Error (MSE). To mitigate computational complexity and eliminate redundant data, a bottleneck approach was used, which reduced the feature space to 1024 while enhancing predictive performance. Further enhancements were achieved through hyperparameter tuning using Polar Bear Optimizer (PBO), leading to significant improvements in the overall model accuracy. The integration of dimensionality reduction and hyperparameter optimization techniques demonstrated significant enhancement in the predictive capabilities of Recurrent Neural Network (RNN) models. This study emphasizes the potential of machine learning techniques in addressing the challenges associated with the rapid quantification of elements in complex fusion related samples.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101994"},"PeriodicalIF":2.7,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145221714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-24DOI: 10.1016/j.nme.2025.101992
Yong Wang , Lina Zhou , Cong Li , Chunlei Feng , Hongbin Ding
High-density cascaded arc plasma has been widely applied in linear plasma devices (LPDs), in which the laser Thomson scattering (LTS) and optical emission spectroscopy (OES) are two popular diagnostic methods for the fundamental parameters, electron density (ne) and electron temperature (Te). However, the complicated LTS setup lacks spatial flexibility, while the accuracy of simple OES is limited. To address this, this study develops a machine learning model based on Support Vector Machine (SVM) with a grid search optimization. This model combines the high accuracy of LTS with the spatial flexibility of OES to predict ne and Te in cascaded arc plasma in DUT-PSI. The model utilizes four pairs of “double-peak” spectral lines, bypassing the complicated calibration for plasma emission spectrum. The results show that when discharged conditions are included as input (Case 1), the model achieves R2 values around 0.97 for ne and about 0.92 for Te. When excluding discharge conditions and using only line intensity ratios (LIRs) as input (Case 2), the R2 values for ne and Te remain approximately 0.90 and 0.80, respectively. The other index, root mean square error (RMSE), follows a similar tendency to R2. These findings demonstrate that the predicted ne and Te in both cases are highly consistent with LTS measurements. Meanwhile, sensitivity analysis reveals that the model’s prediction accuracy is robust to the specific combination of spectral lines selected in both cases. Thus, by integrating the strengths of LTS and OES, this model features calibration-free for plasma spectroscopy and flexible spectral line selection, enabling comprehensive diagnosis of cascaded arc plasma and showing potential for application in other similar LPDs.
{"title":"Machine learning assisted optical emission spectroscopy to determine electron density and electron temperature in a cascaded arc plasma","authors":"Yong Wang , Lina Zhou , Cong Li , Chunlei Feng , Hongbin Ding","doi":"10.1016/j.nme.2025.101992","DOIUrl":"10.1016/j.nme.2025.101992","url":null,"abstract":"<div><div>High-density cascaded arc plasma has been widely applied in linear plasma devices (LPDs), in which the laser Thomson scattering (LTS) and optical emission spectroscopy (OES) are two popular diagnostic methods for the fundamental parameters, electron density (<em>n<sub>e</sub></em>) and electron temperature (<em>T<sub>e</sub></em>). However, the complicated LTS setup lacks spatial flexibility, while the accuracy of simple OES is limited. To address this, this study develops a machine learning model based on Support Vector Machine (SVM) with a grid search optimization. This model combines the high accuracy of LTS with the spatial flexibility of OES to predict <em>n<sub>e</sub></em> and <em>T<sub>e</sub></em> in cascaded arc plasma in DUT-PSI. The model utilizes four pairs of “double-peak” spectral lines, bypassing the complicated calibration for plasma emission spectrum. The results show that when discharged conditions are included as input (Case 1), the model achieves R<sup>2</sup> values around 0.97 for <em>n<sub>e</sub></em> and about 0.92 for <em>T<sub>e</sub></em>. When excluding discharge conditions and using only line intensity ratios (LIRs) as input (Case 2), the R<sup>2</sup> values for <em>n<sub>e</sub></em> and <em>T<sub>e</sub></em> remain approximately 0.90 and 0.80, respectively. The other index, root mean square error (RMSE), follows a similar tendency to R<sup>2</sup>. These findings demonstrate that the predicted <em>n<sub>e</sub></em> and <em>T<sub>e</sub></em> in both cases are highly consistent with LTS measurements. Meanwhile, sensitivity analysis reveals that the model’s prediction accuracy is robust to the specific combination of spectral lines selected in both cases. Thus, by integrating the strengths of LTS and OES, this model features calibration-free for plasma spectroscopy and flexible spectral line selection, enabling comprehensive diagnosis of cascaded arc plasma and showing potential for application in other similar LPDs.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101992"},"PeriodicalIF":2.7,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-20DOI: 10.1016/j.nme.2025.101990
Martina Fellinger , Eduardo Pitthan , Daniel Gautam , Daniel Primetzhofer , Friedrich Aumayr
Retention of hydrogen isotopes in plasma-facing materials is a key challenge for safety and fuel efficiency of nuclear fusion reactors. In realistic reactor environments, simultaneous processes, such as erosion, redeposition, implantation and outgassing, can alter surface compositions and may affect hydrogen isotope retention. In this study, we investigate how thin redeposited layers of tungsten and EUROFER97 influence retention and release of previously implanted deuterium. Using a combination of Elastic Recoil Detection Analysis and Rutherford Backscattering Spectrometry, we quantify deuterium retention during in-situ annealing up to 600 °C. Comparisons between coated and uncoated samples show that redeposited tungsten can act as partial diffusion barrier, preventing deuterium from outgassing. In contrast, redeposited EUROFER97 layers show no such effect and appear virtually transparent to deuterium diffusion. These findings emphasize the critical role of redeposited layers on fuel retention and have implications for wall lifetime estimates and fuel inventory control in fusion devices.
{"title":"Influence of redeposited tungsten and EUROFER97 layers on deuterium retention in plasma-facing materials","authors":"Martina Fellinger , Eduardo Pitthan , Daniel Gautam , Daniel Primetzhofer , Friedrich Aumayr","doi":"10.1016/j.nme.2025.101990","DOIUrl":"10.1016/j.nme.2025.101990","url":null,"abstract":"<div><div>Retention of hydrogen isotopes in plasma-facing materials is a key challenge for safety and fuel efficiency of nuclear fusion reactors. In realistic reactor environments, simultaneous processes, such as erosion, redeposition, implantation and outgassing, can alter surface compositions and may affect hydrogen isotope retention. In this study, we investigate how thin redeposited layers of tungsten and EUROFER97 influence retention and release of previously implanted deuterium. Using a combination of Elastic Recoil Detection Analysis and Rutherford Backscattering Spectrometry, we quantify deuterium retention during in-situ annealing up to 600<!--> <!-->°C. Comparisons between coated and uncoated samples show that redeposited tungsten can act as partial diffusion barrier, preventing deuterium from outgassing. In contrast, redeposited EUROFER97 layers show no such effect and appear virtually transparent to deuterium diffusion. These findings emphasize the critical role of redeposited layers on fuel retention and have implications for wall lifetime estimates and fuel inventory control in fusion devices.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101990"},"PeriodicalIF":2.7,"publicationDate":"2025-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145159327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-20DOI: 10.1016/j.nme.2025.101991
M. Roldán, T. Hernández, F.J. Sánchez
This study investigates the susceptibility of EUROFER reduced-activation ferritic-martensitic (RAFM) steel to stress corrosion cracking (SCC) when exposed to lithium ceramic breeder materials (HCPB environment) at 550 °C. A standardized experimental methodology based on the U-bend configuration was employed to apply well-defined stresses while preserving microstructural integrity. Specimens were subjected to prolonged exposure (up to 4300 h) in direct contact with lithium ceramics, and the resulting damage was characterized using scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Complementary finite element simulations were performed to ensure the applied load remained within the elastic regime, evaluate the stress distribution, and identify the region experiencing maximum stress.
The results reveal that SCC is promoted by the formation of a thin, brittle, chromium-depleted surface layer, resulting from high-temperature oxidation. Cracks nucleate within this chemically and structurally degraded zone and propagate transgranularly under residual stress. A quantitative analysis of crack density and size demonstrates a clear correlation with exposure time and stress level, confirming the critical role of mechanical load in accelerating crack initiation and growth. These findings identify a significant degradation mechanism affecting EUROFER in breeder blanket operating conditions, underscoring the need to control both surface chemistry and residual stresses to ensure long-term structural reliability.
{"title":"Stress corrosion cracking (SCC) in EUROFER RAFM steel subjected to Li-ceramics at 550 °C","authors":"M. Roldán, T. Hernández, F.J. Sánchez","doi":"10.1016/j.nme.2025.101991","DOIUrl":"10.1016/j.nme.2025.101991","url":null,"abstract":"<div><div>This study investigates the susceptibility of EUROFER reduced-activation ferritic-martensitic (RAFM) steel to stress corrosion cracking (SCC) when exposed to lithium ceramic breeder materials (HCPB environment) at 550 °C. A standardized experimental methodology based on the U-bend configuration was employed to apply well-defined stresses while preserving microstructural integrity. Specimens were subjected to prolonged exposure (up to 4300 h) in direct contact with lithium ceramics, and the resulting damage was characterized using scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). Complementary finite element simulations were performed to ensure the applied load remained within the elastic regime, evaluate the stress distribution, and identify the region experiencing maximum stress.</div><div>The results reveal that SCC is promoted by the formation of a thin, brittle, chromium-depleted surface layer, resulting from high-temperature oxidation. Cracks nucleate within this chemically and structurally degraded zone and propagate transgranularly under residual stress. A quantitative analysis of crack density and size demonstrates a clear correlation with exposure time and stress level, confirming the critical role of mechanical load in accelerating crack initiation and growth. These findings identify a significant degradation mechanism affecting EUROFER in breeder blanket operating conditions, underscoring the need to control both surface chemistry and residual stresses to ensure long-term structural reliability.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"45 ","pages":"Article 101991"},"PeriodicalIF":2.7,"publicationDate":"2025-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145120880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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