Pub Date : 2024-11-01DOI: 10.1016/j.nme.2024.101800
Shuyi Chen, Shengli Chen
Radiation damage is a critical concern for materials employed in radiation environments such as space, radiotherapy centers, and nuclear energy systems. Numerous models have been developed to estimate the primary radiation damage. The slightly modified Athermal Recombination-Corrected (mARC)-Displacement per Atom (DPA) model proposes a simple function to describe the atomic displacement near the Threshold Displacement Energy (TDE). The present work systematically investigates the global minimum TDE and the near-TDE mARC-DPA model against experimental electron irradiation damage data for 26 materials. The determined high-accuracy global minimum TDE values are generally consistent with previous studies. The corresponding theoretical calculations agree well with experimental measurements, implying the applicability of the mARC model. Renormalization of certain experimental data is required due to the potential issues related to experimental measurements, the value of resistivity change per Frenkel pair (), or average TDE (). Nevertheless, while some experimental data are supposed to be adjusted, the analysis shows that the ratio of can be definitively determined if assuming the experimental data for the remainders.
{"title":"Systematic study of displacement threshold and the near-threshold primary radiation damage model","authors":"Shuyi Chen, Shengli Chen","doi":"10.1016/j.nme.2024.101800","DOIUrl":"10.1016/j.nme.2024.101800","url":null,"abstract":"<div><div>Radiation damage is a critical concern for materials employed in radiation environments such as space, radiotherapy centers, and nuclear energy systems. Numerous models have been developed to estimate the primary radiation damage. The slightly modified Athermal Recombination-Corrected (mARC)-Displacement per Atom (DPA) model proposes a simple function to describe the atomic displacement near the Threshold Displacement Energy (TDE). The present work systematically investigates the global minimum TDE and the near-TDE mARC-DPA model against experimental electron irradiation damage data for 26 materials. The determined high-accuracy global minimum TDE values are generally consistent with previous studies. The corresponding theoretical calculations agree well with experimental measurements, implying the applicability of the mARC model. Renormalization of certain experimental data is required due to the potential issues related to experimental measurements, the value of resistivity change per Frenkel pair (<span><math><mrow><msub><mi>ρ</mi><mrow><mi>F</mi><mi>P</mi></mrow></msub></mrow></math></span>), or average TDE (<span><math><mrow><msub><mi>E</mi><mi>d</mi></msub></mrow></math></span>). Nevertheless, while some experimental data are supposed to be adjusted, the analysis shows that the ratio of <span><math><mrow><msub><mi>ρ</mi><mrow><mi>F</mi><mi>P</mi></mrow></msub><mo>/</mo><msub><mi>E</mi><mi>d</mi></msub></mrow></math></span> can be definitively determined if assuming the experimental data for the remainders.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101800"},"PeriodicalIF":2.3,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.nme.2024.101801
Hongzhou Yan , Huayan Chen , Wenyan Zhang , Maobing Shuai , Bin Huang
Failure typically occurs during sintering due to high thermal stress and poor strength of LiH ceramics. The short sintering time has shown to be beneficial in preventing excessive grain growth and improving ceramic performance. In this study, we built a genetic algorithm back propagation artificial neural network (GA-BP-ANN) model to predict the strength margins under different work conditions. Sensitivity analysis showed that the thickness and end control time were the most relevant parameters for strength margins, and the GA-BP-ANN model demonstrated the most efficient sintering work condition for a given thickness. Through statistical analysis of the strength margin predicted by the GA-BP-ANN model, we found that the bilinear temperature control method expanded the range of safe sintering conditions by 30% compared to the linear temperature control method. The research results of this study may serve as a reference for the safe and efficient sintering of LiH ceramics.
{"title":"Strength prediction and optimization for microwave sintering of large-dimension lithium hydride ceramics: GA-BP-ANN modeling","authors":"Hongzhou Yan , Huayan Chen , Wenyan Zhang , Maobing Shuai , Bin Huang","doi":"10.1016/j.nme.2024.101801","DOIUrl":"10.1016/j.nme.2024.101801","url":null,"abstract":"<div><div>Failure typically occurs during sintering due to high thermal stress and poor strength of LiH ceramics. The short sintering time has shown to be beneficial in preventing excessive grain growth and improving ceramic performance. In this study, we built a genetic algorithm back propagation artificial neural network (GA-BP-ANN) model to predict the strength margins under different work conditions. Sensitivity analysis showed that the thickness and end control time were the most relevant parameters for strength margins, and the GA-BP-ANN model demonstrated the most efficient sintering work condition for a given thickness. Through statistical analysis of the strength margin predicted by the GA-BP-ANN model, we found that the bilinear temperature control method expanded the range of safe sintering conditions by 30% compared to the linear temperature control method. The research results of this study may serve as a reference for the safe and efficient sintering of LiH ceramics.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101801"},"PeriodicalIF":2.3,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.nme.2024.101790
V.A. Soukhanovskii , S.L. Allen , M.E. Fenstermacher , C.J. Lasnier , A.G. McLean , F. Scotti , E. Kolemen , A. Diallo , S. Gerhardt , S. Kaye , B.P. LeBlanc , R. Maingi , J.E. Menard , R. Raman , A.W. Hyatt , A.W. Leonard , T.H. Osborne , The NSTX and DIII-D Teams
Experimental data from NSTX and DIII-D discharges with the snowflake (SF) divertor configurations are analyzed toward the development of the X-point radiator (XPR) concept. The XPR divertor regime was recently realized in standard divertor configurations in several tokamaks The SF divertor configuration, with an additional poloidal field null nearby the main X-point, could provide additional benefits for the XPR: a higher flux expansion inside the separatrix and an extended private flux region. This may lead to lower temperatures and higher neutral and electron densities, which are thought to be essential for XPR stability, initiation, and impurity containment. In this work, 4 MW NBI-heated H-mode NSTX discharges and 3–5 MW NBI-heated H-mode DIII-D discharges with SF-minus and SF-plus divertors, with the ion drift toward the lower divertor, with and without D and CD seeding, were analyzed. Many experimental XPR features were found, including good or slightly degraded H-mode confinement, significant ELM size reduction, nearly complete divertor power detachment and a significant divertor radiated power loss. However, evidence of the XPR extending into the confined region was inconclusive in the NSTX tokamak, while in DIII-D, a number of discharges demonstrated a stable MARFE-like structure inside the separatrix over a wide operating space. The present analysis supports the SF divertor as a good candidate for further XPR scenario development in DIII-D and NSTX-U.
对采用雪花（SF）分流器配置的 NSTX 和 DIII-D 放电的实验数据进行了分析，以发展 X 点辐射器（XPR）概念。在主X点附近有一个附加极性场空的SF岔流器配置，可以为XPR提供额外的好处：分离矩阵内部更高的通量扩展和更大的私人通量区域。这可能会导致更低的温度和更高的中性密度和电子密度，而这些被认为是 XPR 的稳定性、启动和杂质遏制所必需的。在这项工作中，分析了带有 SF-minus 和 SF-plus 分流器的 4 兆瓦 NBI 加热 H 模式 NSTX 放电和 3-5 兆瓦 NBI 加热 H 模式 DIII-D 放电，离子 B×∇B 漂向较低的分流器，有无 D2 和 CD4 播种。发现了许多 XPR 实验特征，包括良好或轻微退化的 H 模式约束、显著缩小的 ELM 尺寸、几乎完全脱离的分流器功率以及显著的分流器辐射功率损失。然而，在NSTX托卡马克中，XPR延伸到约束区域的证据并不确凿，而在DIII-D中，一些放电显示了分离矩阵内部在较宽的运行空间内存在稳定的类似MARFE的结构。目前的分析支持将 SF 分流器作为在 DIII-D 和 NSTX-U 中进一步开发 XPR 方案的良好候选者。
{"title":"In search of X-point radiator regime features in NSTX and DIII-D discharges with the snowflake divertor","authors":"V.A. Soukhanovskii , S.L. Allen , M.E. Fenstermacher , C.J. Lasnier , A.G. McLean , F. Scotti , E. Kolemen , A. Diallo , S. Gerhardt , S. Kaye , B.P. LeBlanc , R. Maingi , J.E. Menard , R. Raman , A.W. Hyatt , A.W. Leonard , T.H. Osborne , The NSTX and DIII-D Teams","doi":"10.1016/j.nme.2024.101790","DOIUrl":"10.1016/j.nme.2024.101790","url":null,"abstract":"<div><div>Experimental data from NSTX and DIII-D discharges with the snowflake (SF) divertor configurations are analyzed toward the development of the X-point radiator (XPR) concept. The XPR divertor regime was recently realized in standard divertor configurations in several tokamaks The SF divertor configuration, with an additional poloidal field null nearby the main X-point, could provide additional benefits for the XPR: a higher flux expansion inside the separatrix and an extended private flux region. This may lead to lower temperatures and higher neutral and electron densities, which are thought to be essential for XPR stability, initiation, and impurity containment. In this work, 4 MW NBI-heated H-mode NSTX discharges and 3–5 MW NBI-heated H-mode DIII-D discharges with SF-minus and SF-plus divertors, with the ion <span><math><mrow><mi>B</mi><mo>×</mo><mo>∇</mo><mi>B</mi></mrow></math></span> drift toward the lower divertor, with and without D<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> and CD<span><math><msub><mrow></mrow><mrow><mn>4</mn></mrow></msub></math></span> seeding, were analyzed. Many experimental XPR features were found, including good or slightly degraded H-mode confinement, significant ELM size reduction, nearly complete divertor power detachment and a significant divertor radiated power loss. However, evidence of the XPR extending into the confined region was inconclusive in the NSTX tokamak, while in DIII-D, a number of discharges demonstrated a stable MARFE-like structure inside the separatrix over a wide operating space. The present analysis supports the SF divertor as a good candidate for further XPR scenario development in DIII-D and NSTX-U.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101790"},"PeriodicalIF":2.3,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.nme.2024.101798
Tao Wang , Jie Li , Pan Dong , Qi Zhu , Jiao Jiao Zhou , Y.W. You , Xiang-Shan Kong
Titanium (Ti) hydrides are frequently utilized as neutron moderators and structural components in environments where neutrons are present. However, the presence of vacancies, which are created by neutron irradiation, has a considerable impact on the service performance of these materials. In order to gain insight into the underlying micro-mechanisms, a systematic ab initio study was conducted with the aim of understanding the dissolution and diffusion of hydrogen in δ-TiH2. The findings indicate that interstitial hydrogen atoms are energetically favorable to occupy the sites surrounded by four lattice-point hydrogen atoms, with a dissolution energy of 0.55 eV. It is energetically unfavorable for hydrogen atoms to accumulate at interstitial sites in δ-TiH2. It has been demonstrated that vacancies can provide favorable spaces for the dissolution of hydrogen. Single Ti vacancy can trap up to 6 H atoms, and the cumulative binding energy of 6 H atoms with a Ti vacancy reaches 1.31 eV. The chemical potential of hydrogen has considerable influence on the interactions among interstitial H atoms and that between vacancies and hydrogen atoms. Ultimately, the density of states and difference charge density were employed to elucidate the underlying mechanisms that govern the interactions between hydrogen and vacancies.
在存在中子的环境中，钛（Ti）氢化物经常被用作中子慢化剂和结构组件。然而，中子辐照产生的空位对这些材料的使用性能有相当大的影响。为了深入了解潜在的微观机制，我们进行了一项系统的 ab initio 研究，目的是了解氢在δ-TiH2 中的溶解和扩散。研究结果表明，间隙氢原子在能量上有利于占据由四个晶格点氢原子包围的位点，其溶解能为 0.55 eV。从能量上讲，氢原子不利于在 δ-TiH2 的间隙位点聚集。事实证明，空位可以为氢的溶解提供有利的空间。单个钛空位可捕获多达 6 个氢原子，6 个氢原子与一个钛空位的累积结合能达到 1.31 eV。氢的化学势对间隙氢原子之间以及空位与氢原子之间的相互作用有很大影响。最终，利用状态密度和差电荷密度阐明了氢与空位之间相互作用的内在机制。
{"title":"The energetics and kinetics of H in δ-TiH2: Ab initio study","authors":"Tao Wang , Jie Li , Pan Dong , Qi Zhu , Jiao Jiao Zhou , Y.W. You , Xiang-Shan Kong","doi":"10.1016/j.nme.2024.101798","DOIUrl":"10.1016/j.nme.2024.101798","url":null,"abstract":"<div><div>Titanium (Ti) hydrides are frequently utilized as neutron moderators and structural components in environments where neutrons are present. However, the presence of vacancies, which are created by neutron irradiation, has a considerable impact on the service performance of these materials. In order to gain insight into the underlying micro-mechanisms, a systematic <em>ab initio</em> study was conducted with the aim of understanding the dissolution and diffusion of hydrogen in δ-TiH<sub>2</sub>. The findings indicate that interstitial hydrogen atoms are energetically favorable to occupy the sites surrounded by four lattice-point hydrogen atoms, with a dissolution energy of 0.55 eV. It is energetically unfavorable for hydrogen atoms to accumulate at interstitial sites in δ-TiH<sub>2</sub>. It has been demonstrated that vacancies can provide favorable spaces for the dissolution of hydrogen. Single Ti vacancy can trap up to 6 H atoms, and the cumulative binding energy of 6 H atoms with a Ti vacancy reaches 1.31 eV. The chemical potential of hydrogen has considerable influence on the interactions among interstitial H atoms and that between vacancies and hydrogen atoms. Ultimately, the density of states and difference charge density were employed to elucidate the underlying mechanisms that govern the interactions between hydrogen and vacancies.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101798"},"PeriodicalIF":2.3,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-31DOI: 10.1016/j.nme.2024.101799
Jong-Dae Hong , Hongryul Oh , Daehyeok Ahn , Dongchan Jang , Hyun-Gil Kim , JaeYong Kim , Hyochan Kim , Martin Ševeček
The development of accident tolerant fuel (ATF) cladding has been encouraged to satisfy increased nuclear safety demands under accident conditions since Fukushima accident. Coating techniques using oxidation-resistant materials, such as Cr and Al, on existing Zr-alloy claddings have been widely applied as short-term solutions. However, coating delamination due to poor adhesion may reduce its benefits, such as low waterside corrosion/oxidation rates and fretting resistance, which necessitates accurate evaluation of coating adhesion suitability. In this study, micro-mechanical tests, micro-cantilever bending test and surface and interfacial cutting analysis system test, were conducted to qualitatively and quantitatively evaluate adhesion properties on a coated ATF cladding. In situ scanning electron microscopy-based micro-cantilever bending tests were performed using a pico-indenter equipped with a diamond flat tip. We present the results for magnetron-sputtered Cr-coated ATF claddings in detail. Micro-cantilever tests on the Cr-Zr interface revealed that deformation and failure primarily occurred in the Zr substrate, rather than at the interface. And the Cr-coated cladding showed highly adherent mechanical bonds, as evidenced by the interfacial strength and elastic modulus. SAICAS tests confirmed that peeling of the coating layer occurred only when the applied force exceeded the cutting force of the coating layer. The experimental results suggest that the Cr-coated cladding exhibited a sufficiently adherent mechanical bond to prevent delamination of the coating.
{"title":"Micro-mechanical evaluations of adhesion properties for Cr-coated accident tolerant fuel cladding","authors":"Jong-Dae Hong , Hongryul Oh , Daehyeok Ahn , Dongchan Jang , Hyun-Gil Kim , JaeYong Kim , Hyochan Kim , Martin Ševeček","doi":"10.1016/j.nme.2024.101799","DOIUrl":"10.1016/j.nme.2024.101799","url":null,"abstract":"<div><div>The development of accident tolerant fuel (ATF) cladding has been encouraged to satisfy increased nuclear safety demands under accident conditions since Fukushima accident. Coating techniques using oxidation-resistant materials, such as Cr and Al, on existing Zr-alloy claddings have been widely applied as short-term solutions. However, coating delamination due to poor adhesion may reduce its benefits, such as low waterside corrosion/oxidation rates and fretting resistance, which necessitates accurate evaluation of coating adhesion suitability. In this study, micro-mechanical tests, micro-cantilever bending test and surface and interfacial cutting analysis system test, were conducted to qualitatively and quantitatively evaluate adhesion properties on a coated ATF cladding. <em>In situ</em> scanning electron microscopy-based micro-cantilever bending tests were performed using a pico-indenter equipped with a diamond flat tip. We present the results for magnetron-sputtered Cr-coated ATF claddings in detail. Micro-cantilever tests on the Cr-Zr interface revealed that deformation and failure primarily occurred in the Zr substrate, rather than at the interface. And the Cr-coated cladding showed highly adherent mechanical bonds, as evidenced by the interfacial strength and elastic modulus. SAICAS tests confirmed that peeling of the coating layer occurred only when the applied force exceeded the cutting force of the coating layer. The experimental results suggest that the Cr-coated cladding exhibited a sufficiently adherent mechanical bond to prevent delamination of the coating.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101799"},"PeriodicalIF":2.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-31DOI: 10.1016/j.nme.2024.101789
K. Schmid , T. Wauters
Substituting Beryllium (Be) with Tungsten (W) as material for the first wall gives rise to new challenges for the ITER project. The additional W at the main chamber could result in a significant influx of high-Z impurities into the plasma owing to the higher particle energies expected at the main chamber wall compared to the divertor. Removing the impurity gettering ability of Be, may require the use of boronization to reduce the partial pressure of low-Z impurities like water and Oxygen, however this potentially introduces the caveat of increased T-retention by co-deposition with Boron (B). Based on existing background plasma solutions with Ne as main radiating impurity the erosion and migration of W and B are modeled using the WallDYN approach. The results on W erosion are strongly affected by transport assumptions and the erosion rates are dominated by Ne- and W-self-sputtering by highly charged W and Ne ions whereas erosion by charge exchange D neutrals is negligible in comparison. The B migration calculations allow to estimate the lifetime of boronization layers which is very short in the heavily loaded plasma wetted regions but can be up to in remote areas where it is only limited by D-CX erosion. Test simulations of a B-dropper during diverted plasma operation suggest that it mainly deposits B in the heavily loaded areas and thus is not effective in replenishing boronization layers in remote areas which are meant for impurity gettering. In summary this work suggests that based on existing data, a transition to W does not hamper the ITER project from the PWI perspective. However, it also shows that large uncertainties remain with respect to the W-plasma transport, boronization layer sputter yields and T/B ratios for retention calculations.
用钨（W）代替铍（Be）作为第一壁的材料给热核实验堆项目带来了新的挑战。由于主室壁的粒子能量预期高于分流器，主室增加 W 可能会导致高 Z 杂质大量涌入等离子体。要消除铍的杂质吸附能力，可能需要使用硼化来降低低 Z 杂质（如水和氧）的分压，但这可能会带来与硼（B）共沉积而增加 T 保留的警告。根据以 Ne 为主要辐射杂质的现有背景等离子体解决方案，使用 WallDYN 方法对 W 和 B 的侵蚀和迁移进行了建模。W 的侵蚀结果受传输假设的影响很大，侵蚀率主要是由高电荷 W 和 Ne 离子的 Ne 和 W 自溅射引起的，而电荷交换 D 中性离子的侵蚀相比之下可以忽略不计。通过硼迁移计算，可以估算出硼化层的寿命，在高负荷等离子体润湿区域，硼化层的寿命非常短，但在偏远区域，硼化层的寿命可长达 104 秒，在这些区域，硼化层的寿命仅受 D-CX 侵蚀的限制。在分流等离子体运行期间对硼滴注器进行的测试模拟表明，它主要将硼沉积在高负荷区域，因此无法有效补充偏远区域的硼化层，而偏远区域的硼化层是用于杂质脱碳的。总之，这项工作表明，根据现有数据，从 PWI 的角度来看，向 W 的过渡不会妨碍热核实验堆项目。不过，它也表明，在 W 等离子体传输、硼化层溅射产量和用于保留计算的 T/B 比率方面，仍然存在很大的不确定性。
{"title":"Full W ITER: Assessment of expected W erosion and implications of boronization on fuel retention","authors":"K. Schmid , T. Wauters","doi":"10.1016/j.nme.2024.101789","DOIUrl":"10.1016/j.nme.2024.101789","url":null,"abstract":"<div><div>Substituting Beryllium (Be) with Tungsten (W) as material for the first wall gives rise to new challenges for the ITER project. The additional W at the main chamber could result in a significant influx of high-Z impurities into the plasma owing to the higher particle energies expected at the main chamber wall compared to the divertor. Removing the impurity gettering ability of Be, may require the use of boronization to reduce the partial pressure of low-Z impurities like water and Oxygen, however this potentially introduces the caveat of increased T-retention by co-deposition with Boron (B). Based on existing background plasma solutions with Ne as main radiating impurity the erosion and migration of W and B are modeled using the WallDYN approach. The results on W erosion are strongly affected by transport assumptions and the erosion rates are dominated by Ne- and W-self-sputtering by highly charged W and Ne ions whereas erosion by charge exchange D neutrals is negligible in comparison. The B migration calculations allow to estimate the lifetime of boronization layers which is very short in the heavily loaded plasma wetted regions but can be up to <span><math><mrow><mo>></mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup><mspace></mspace><mi>s</mi></mrow></math></span> in remote areas where it is only limited by D-CX erosion. Test simulations of a B-dropper during diverted plasma operation suggest that it mainly deposits B in the heavily loaded areas and thus is not effective in replenishing boronization layers in remote areas which are meant for impurity gettering. In summary this work suggests that based on existing data, a transition to W does not hamper the ITER project from the PWI perspective. However, it also shows that large uncertainties remain with respect to the W-plasma transport, boronization layer sputter yields and T/B ratios for retention calculations.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101789"},"PeriodicalIF":2.3,"publicationDate":"2024-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-30DOI: 10.1016/j.nme.2024.101797
K.R. Yang , J.Y. Chen , C.R. Zu , W.Y. Ni , D.P. Liu , S.G. Liu , B. Cui , S.Y. Dai
Extrinsic noble impurities seeding has been commonly used to reduce the heat flux on divertor target. However, the physical sputtering yield on the target could be obviously enhanced due to larger mass of noble impurities. On the other hand, it has been reported that tungsten fuzz can suppress the physical sputtering due to the trapping effect on sputtered particles. Hence, it is interesting to check the erosion behaviors of tungsten fuzz under the irradiation of noble impurities. Recently, experiments of He/Ar mixed plasma irradiation on W target were conducted on LP-MIES device. Dedicated simulations have been performed by SURO-FUZZ code to study the impact of Ar flux on fuzz growth and erosion, which can well reproduce the experimental measurements on LP-MIES. For the case of pure He incidence, the growth of porous nanostructure leads to an obvious reduction in the fraction of the implanted He particles, which stabilizes to 15 % when the fuzz layer thickness exceeds 1500 nm. For He/Ar mixed plasma irradiation, the dependence of the position of the net sputtering on the local porosity has been investigated in detail. It is found that the net physical sputtering mainly occurs in the regions with the local porosity larger than 0.6.
外来惰性杂质播种通常用于降低分流靶上的热通量。然而，由于惰性杂质的质量较大，靶上的物理溅射产率会明显提高。另一方面，据报道，钨毛细管由于对溅射粒子的捕获作用，可以抑制物理溅射。因此，研究钨毛细管在惰性杂质辐照下的侵蚀行为很有意义。最近，在 LP-MIES 设备上进行了 He/Ar 混合等离子体辐照 W 靶的实验。SURO-FUZZ代码进行了专门的模拟，研究了Ar通量对模糊生长和侵蚀的影响，很好地再现了LP-MIES上的实验测量结果。在纯 He 入射的情况下，多孔纳米结构的生长导致植入 He 粒子的比例明显下降，当模糊层厚度超过 1500 nm 时，这一比例稳定在 15%。对于 He/Ar 混合等离子体辐照，我们详细研究了净溅射位置与局部孔隙率的关系。研究发现，物理净溅射主要发生在局部孔隙率大于 0.6 的区域。
{"title":"Simulations of tungsten fuzz growth and erosion under He/Ar mixed plasma irradiation on LP-MIES","authors":"K.R. Yang , J.Y. Chen , C.R. Zu , W.Y. Ni , D.P. Liu , S.G. Liu , B. Cui , S.Y. Dai","doi":"10.1016/j.nme.2024.101797","DOIUrl":"10.1016/j.nme.2024.101797","url":null,"abstract":"<div><div>Extrinsic noble impurities seeding has been commonly used to reduce the heat flux on divertor target. However, the physical sputtering yield on the target could be obviously enhanced due to larger mass of noble impurities. On the other hand, it has been reported that tungsten fuzz can suppress the physical sputtering due to the trapping effect on sputtered particles. Hence, it is interesting to check the erosion behaviors of tungsten fuzz under the irradiation of noble impurities. Recently, experiments of He/Ar mixed plasma irradiation on W target were conducted on LP-MIES device. Dedicated simulations have been performed by SURO-FUZZ code to study the impact of Ar flux on fuzz growth and erosion, which can well reproduce the experimental measurements on LP-MIES. For the case of pure He incidence, the growth of porous nanostructure leads to an obvious reduction in the fraction of the implanted He particles, which stabilizes to 15 % when the fuzz layer thickness exceeds 1500 nm. For He/Ar mixed plasma irradiation, the dependence of the position of the net sputtering on the local porosity has been investigated in detail. It is found that the net physical sputtering mainly occurs in the region<del>s</del> with the local porosity larger than 0.6.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101797"},"PeriodicalIF":2.3,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-30DOI: 10.1016/j.nme.2024.101795
Q. Zhang , F. Ding , B.C. Qi , L.Y. Meng , L. Yu , C.Y. Zhang , Z.H. Hu , R. Ding , L. Wang , H.S. Zhou , G.N. Luo , Z.S. Yang , X. Yang , EAST Team
Tungsten (W) is one of the preferred plasma-facing materials for future fusion reactors because of the advantages of high melting point, low physical sputtering rate and low fuel retention. The lifetime and service performance of W materials are limited by erosion processes. In recent years, tungsten deuteride molecular (WD) sputtering has been discovered in tokamak. Studying WD sputtering helps to better understand the erosion of tungsten materials in tokamak. EAST adopts the method of injecting impurity gas in the divertor to alleviate the particle flux and heat flux bombarding the tungsten divertor, and CD4 is one of the impurities used. CD4 injection experiments on EAST show that after CD4 is injected from the upper outer (UO) divertor target, despite that the electron temperature (Te) around the strike point on the UO divertor target drops to about 8 eV, strong WD sputtering occurs in the far scrape-off layer (SOL) region. The divertor probe data shows that after CD4 injection, the particle flux from the upstream plasma onto the divertor split into two bands, creating a new particle flux strike point in the far SOL region. The energy of incident particles at the original strike point is significantly reduced, while the energy of incident particles at the far SOL region is enhanced. The edge electron density profile at mid-plane indicates that CD4 injection causes an increase of density in the SOL, which could improve the coupling of Lower-Hybrid Wave (LHW) with the edge plasma as evidenced by the decreasing reflected power of LHW. The increase in absorbed power of LHW could change the particle and energy transport in the edge plasma, thus plays an important role in the enhanced WD sputtering in the far SOL region after CD4 injection.
钨（W）具有高熔点、低物理溅射率和低燃料滞留等优点，是未来聚变反应堆的首选等离子体面材料之一。W 材料的使用寿命和使用性能受到侵蚀过程的限制。近年来，在托卡马克中发现了氘化钨分子（WD）溅射。研究 WD 溅射有助于更好地了解托卡马克中钨材料的侵蚀过程。EAST采用在分流器中注入杂质气体的方法，以减轻轰击钨分流器的粒子流和热流，CD4就是其中一种杂质。在 EAST 上进行的 CD4 注入实验表明，从上外层（UO）分流靶注入 CD4 后，尽管 UO 分流靶上打击点周围的电子温度（Te）降至约 8 eV，但在远刮除层（SOL）区域仍发生了强烈的 WD 溅射。分流器探测数据显示，在注入 CD4 之后，从上游等离子体到分流器的粒子流分成了两个波段，在远 SOL 区域形成了一个新的粒子流撞击点。原撞击点的入射粒子能量显著降低，而远 SOL 区域的入射粒子能量则有所提高。中平面的边缘电子密度曲线表明，CD4 注入会导致 SOL 密度增加，从而改善下杂波（LHW）与边缘等离子体的耦合，这一点从 LHW 反射功率的下降可以得到证明。LHW 吸收功率的增加会改变边缘等离子体中的粒子和能量传输，从而在 CD4 注入后增强远 SOL 区域的 WD 溅射中发挥重要作用。
{"title":"The effect of CD4 injection on WD molecule sputtering at the divertor target in EAST","authors":"Q. Zhang , F. Ding , B.C. Qi , L.Y. Meng , L. Yu , C.Y. Zhang , Z.H. Hu , R. Ding , L. Wang , H.S. Zhou , G.N. Luo , Z.S. Yang , X. Yang , EAST Team","doi":"10.1016/j.nme.2024.101795","DOIUrl":"10.1016/j.nme.2024.101795","url":null,"abstract":"<div><div>Tungsten (W) is one of the preferred plasma-facing materials for future fusion reactors because of the advantages of high melting point, low physical sputtering rate and low fuel retention. The lifetime and service performance of W materials are limited by erosion processes. In recent years, tungsten deuteride molecular (WD) sputtering has been discovered in tokamak. Studying WD sputtering helps to better understand the erosion of tungsten materials in tokamak. EAST adopts the method of injecting impurity gas in the divertor to alleviate the particle flux and heat flux bombarding the tungsten divertor, and CD<sub>4</sub> is one of the impurities used. CD<sub>4</sub> injection experiments on EAST show that after CD<sub>4</sub> is injected from the upper outer (UO) divertor target, despite that the electron temperature (<em>T</em><sub>e</sub>) around the strike point on the UO divertor target drops to about 8 eV, strong WD sputtering occurs in the far scrape-off layer (SOL) region. The divertor probe data shows that after CD<sub>4</sub> injection, the particle flux from the upstream plasma onto the divertor split into two bands, creating a new particle flux strike point in the far SOL region. The energy of incident particles at the original strike point is significantly reduced, while the energy of incident particles at the far SOL region is enhanced. The edge electron density profile at mid-plane indicates that CD<sub>4</sub> injection causes an increase of density in the SOL, which could improve the coupling of Lower-Hybrid Wave (LHW) with the edge plasma as evidenced by the decreasing reflected power of LHW. The increase in absorbed power of LHW could change the particle and energy transport in the edge plasma, thus plays an important role in the enhanced WD sputtering in the far SOL region after CD<sub>4</sub> injection.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101795"},"PeriodicalIF":2.3,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573368","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-29DOI: 10.1016/j.nme.2024.101793
M. Oya , K. Hoshino , N. Asakura , Y. Sakamoto , N. Ohno , K. Hanada
We developed and performed a 3D Monte-Carlo simulation on local erosion and deposition in outer divertor target of JA-DEMO. The local erosion and deposition were evaluated considering the divertor plasma parameters and the roof shape of W-monoblocks. First, for local erosion simulation, the trajectories of D ions and impurity (He and Ar) ions were traced before irradiating the monoblock surface. The physical sputtering was calculated by these ions irradiation, considering their charge states, incident-energies and -angles. The highest sputtering flux was produced by multiply-charged Ar ions (Ar3+–Ar5+). The sputtering flux strongly depended on the poloidal positions along the divertor target. Although almost no erosion (sputtering) was obtained in low-temperature zone (∼1 eV), the erosion occurred in mid- (∼10 eV) and high-temperature (>10 eV) zone. Second, for local deposition simulation, the trajectories of W atoms emitted from the monoblock surface were traced. After transport (including ionization and recombination) in the plasma, W atoms and ions were deposited on the monoblock surface. The deposition occurred even on the area where plasmas did not irradiate (shadow). This was due to perpendicular diffusion to magnetic field lines, gyro-orbit effects for W ions and straight-line motion for neutral W atoms. The poloidal distribution of the deposition fluxes was similar to that of the sputtering fluxes. In low-temperature zone, no deposition flux occurred due to very low sputtering flux. The deposition flux in mid-temperature zone increased significantly and that in high-temperature zone remained high.
我们开发并进行了 JA-DEMO 外岔道靶局部侵蚀和沉积的三维蒙特卡洛模拟。考虑到辐照器等离子体参数和 W 单块的顶盖形状，我们对局部侵蚀和沉积进行了评估。首先，为了进行局部侵蚀模拟，在辐照单块表面之前跟踪了 D 离子和杂质（He 和 Ar）离子的轨迹。考虑到这些离子的电荷状态、入射能量和角度，通过这些离子的辐照计算出物理溅射。多电荷氩离子（Ar3+-Ar5+）产生的溅射通量最高。溅射通量在很大程度上取决于沿分流靶的极性位置。虽然在低温区（∼1 eV）几乎没有侵蚀（溅射），但在中温（∼10 eV）和高温（>10 eV）区出现了侵蚀。其次，为了进行局部沉积模拟，对从单块表面发射的 W 原子的轨迹进行了追踪。在等离子体中传输（包括电离和重组）后，W 原子和离子沉积在单体表面。沉积甚至发生在等离子体未照射的区域（阴影）。这是由于垂直于磁场线的扩散、W 离子的陀螺轨道效应和中性 W 原子的直线运动。沉积通量的极性分布与溅射通量相似。在低温区，由于溅射通量非常低，因此没有沉积通量。中温区的沉积通量显著增加，而高温区的沉积通量仍然很高。
{"title":"Evaluation of local erosion and deposition on the W-monoblock of JA-DEMO divertor","authors":"M. Oya , K. Hoshino , N. Asakura , Y. Sakamoto , N. Ohno , K. Hanada","doi":"10.1016/j.nme.2024.101793","DOIUrl":"10.1016/j.nme.2024.101793","url":null,"abstract":"<div><div>We developed and performed a 3D Monte-Carlo simulation on local erosion and deposition in outer divertor target of JA-DEMO. The local erosion and deposition were evaluated considering the divertor plasma parameters and the roof shape of W-monoblocks. First, for local erosion simulation, the trajectories of D ions and impurity (He and Ar) ions were traced before irradiating the monoblock surface. The physical sputtering was calculated by these ions irradiation, considering their charge states, incident-energies and -angles. The highest sputtering flux was produced by multiply-charged Ar ions (Ar<sup>3+</sup>–Ar<sup>5+</sup>). The sputtering flux strongly depended on the poloidal positions along the divertor target. Although almost no erosion (sputtering) was obtained in low-temperature zone (∼1 eV), the erosion occurred in mid- (∼10 eV) and high-temperature (>10 eV) zone. Second, for local deposition simulation, the trajectories of W atoms emitted from the monoblock surface were traced. After transport (including ionization and recombination) in the plasma, W atoms and ions were deposited on the monoblock surface. The deposition occurred even on the area where plasmas did not irradiate (shadow). This was due to perpendicular diffusion to magnetic field lines, gyro-orbit effects for W ions and straight-line motion for neutral W atoms. The poloidal distribution of the deposition fluxes was similar to that of the sputtering fluxes. In low-temperature zone, no deposition flux occurred due to very low sputtering flux. The deposition flux in mid-temperature zone increased significantly and that in high-temperature zone remained high.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101793"},"PeriodicalIF":2.3,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142573370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-29DOI: 10.1016/j.nme.2024.101792
Heng Li , Xin Zhang , Yuhong Xu , Guangjiu Lei , Sanqiu Liu , Katsuyoshi Tsumori , Haruhisa Nakano , Masaki Osakabe , Mitsutaka Isobe , Shoichi Okamura , Akihiro Shimizu , Kunihiro Ogawa , Hiromi Takahashi , Zilin Cui , Jun Hu , Yiqin Zhu , Xiaolong Li , Huaqing Zheng , Xiaoqiao Liu , Shaofei Geng , CFQS team
This study investigates the effect of oxygen and copper impurities on the work function of the Cs/H/Mo (001) surface based on the Density Functional Theory (DFT) method. First, the deposition of 2/16 θ impurities on the Cs0.5/H0.5/Mo (001) surface (the subscript 0.5 represents 8/16 θ coverage) is studied. It is found that the deposition of impurities beneath the cesium layer and oxygen impurities as atoms, and in a high-symmetry configuration, both lower the surface system energy. As the impurity coverage increases, it is observed that impurity deposition with a coverage of less than or equal to 8/16 θ effectively reduces the work function of the Cs0.5/H0.5/Mo (001) surface. However, as the cesium and hydrogen coverage increases, the impurities are no longer effective at reducing the work function. Moreover, when the cesium coverage reaches 16/16 θ, the surface work function approaches that of a cesium metal surface. Another important discovery is that when oxygen impurities are deposited above the cesium layer on the Cs0.5/H0.5/Mo (001) surface, a reduction in the surface work function is observed. This anomalous phenomenon is attributed to significant charge polarization caused by the deposition of oxygen impurities. The migration barriers of impurities traversing the dense cesium layer to the Mo (001) substrate are evaluated using the climbing image nudged elastic band (CI-NEB) method. Oxygen impurities tend to traverse the cesium layer in molecular form, facing a minimum barrier of 0.52 eV, while copper atoms encounter a lower barrier of 0.09 eV when traversing the cesium layer.
{"title":"Effect of oxygen or copper impurities on the work function of cesiated surfaces under co-existence with hydrogen: A study about negative hydrogen ion sources for neutral beam injection systems","authors":"Heng Li , Xin Zhang , Yuhong Xu , Guangjiu Lei , Sanqiu Liu , Katsuyoshi Tsumori , Haruhisa Nakano , Masaki Osakabe , Mitsutaka Isobe , Shoichi Okamura , Akihiro Shimizu , Kunihiro Ogawa , Hiromi Takahashi , Zilin Cui , Jun Hu , Yiqin Zhu , Xiaolong Li , Huaqing Zheng , Xiaoqiao Liu , Shaofei Geng , CFQS team","doi":"10.1016/j.nme.2024.101792","DOIUrl":"10.1016/j.nme.2024.101792","url":null,"abstract":"<div><div>This study investigates the effect of oxygen and copper impurities on the work function of the Cs/H/Mo (001) surface based on the Density Functional Theory (DFT) method. First, the deposition of 2/16 θ impurities on the Cs<sub>0.5</sub>/H<sub>0.5</sub>/Mo (001) surface (the subscript 0.5 represents 8/16 θ coverage) is studied. It is found that the deposition of impurities beneath the cesium layer and oxygen impurities as atoms, and in a high-symmetry configuration, both lower the surface system energy. As the impurity coverage increases, it is observed that impurity deposition with a coverage of less than or equal to 8/16 θ effectively reduces the work function of the Cs<sub>0.5</sub>/H<sub>0.5</sub>/Mo (001) surface. However, as the cesium and hydrogen coverage increases, the impurities are no longer effective at reducing the work function. Moreover, when the cesium coverage reaches 16/16 θ, the surface work function approaches that of a cesium metal surface. Another important discovery is that when oxygen impurities are deposited above the cesium layer on the Cs<sub>0.5</sub>/H<sub>0.5</sub>/Mo (001) surface, a reduction in the surface work function is observed. This anomalous phenomenon is attributed to significant charge polarization caused by the deposition of oxygen impurities. The migration barriers of impurities traversing the dense cesium layer to the Mo (001) substrate are evaluated using the climbing image nudged elastic band (CI-NEB) method. Oxygen impurities tend to traverse the cesium layer in molecular form, facing a minimum barrier of 0.52 eV, while copper atoms encounter a lower barrier of 0.09 eV when traversing the cesium layer.</div></div>","PeriodicalId":56004,"journal":{"name":"Nuclear Materials and Energy","volume":"41 ","pages":"Article 101792"},"PeriodicalIF":2.3,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142653449","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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