The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
S L Dudarev - One of the best experts on this subject based on the ideXlab platform.
-
neutron induced dpa transmutations gas production and helium embrittlement of Fusion materials
Journal of Nuclear Materials, 2013Co-Authors: M R Gilbert, S L Dudarev, S Zheng, L W Packer, Duc Nguyenmanh, -ch. J. SubletAbstract:In a Fusion reactor materials will be subjected to significant fluxes of high-energy neutrons. As well as causing radiation damage, the neutrons also initiate nuclear reactions leading to changes in the chemical composition of materials (transmutation). Many of these reactions produce gases, particularly helium, which cause additional swelling and embrittlement of materials. This paper investigates, using a combination of neutron-transport and inventory calculations, the variation in displacements per atom (dpa) and helium production levels as a function of position within the high flux regions of a recent conceptual model for the ‘next-step’ Fusion device DEMO. Subsequently, the gas production rates are used to provide revised estimates, based on new density-functional-theory results, for the critical component lifetimes associated with the helium-induced grain-boundary embrittlement of materials. The revised estimates give more optimistic projections for the lifetimes of materials in a Fusion Power Plant compared to a previous study, while at the same time indicating that helium embrittlement remains one of the most significant factors controlling the structural integrity of Fusion Power Plant components.
-
an integrated model for materials in a Fusion Power Plant transmutation gas production and helium embrittlement under neutron irradiation
Nuclear Fusion, 2012Co-Authors: M R Gilbert, S L Dudarev, S Zheng, L W Packer, -ch. J. SubletAbstract:The high-energy, high-intensity neutron fluxes produced by the Fusion plasma will have a significant life-limiting impact on reactor components in both experimental and commercial Fusion devices. As well as producing defects, the neutrons bombarding the materials initiate nuclear reactions, leading to transmutation of the elemental atoms. Products of many of these reactions are gases, particularly helium, which can cause swelling and embrittlement of materials.This paper integrates several different computational techniques to produce a comprehensive picture of the response of materials to neutron irradiation, enabling the assessment of structural integrity of components in a Fusion Power Plant. Neutron-transport calculations for a model of the next-step Fusion device DEMO reveal the variation in exposure conditions in different components of the vessel, while inventory calculations quantify the associated implications for transmutation and gas production. The helium production rates are then used, in conjunction with a simple model for He-induced grain-boundary embrittlement based on electronic-structure density functional theory calculations, to estimate the timescales for susceptibility to grain-boundary failure in different Fusion-relevant materials. There is wide variation in the predicted grain-boundary-failure lifetimes as a function of both microstructure and chemical composition, with some conservative predictions indicating much less than the required lifetime for components in a Fusion Power Plant.
-
first principles modeling of tungsten based alloys for Fusion Power Plant applications
Key Engineering Materials, 2011Co-Authors: Duc Nguyen Manh, M. Muzyk, K J Kurzydlowski, N Baluc, M Rieth, S L DudarevAbstract:We describe a comprehensive ab initio investigation of phase stability and mechanical properties of W-Ta and W-V alloys, which are candidate materials for Fusion Power Plant applications. The ab initio density functional calculations compare enthalpies of mixing for alternative ordered atomic structures of the alloys, corresponding to the same chemical composition. Combining the ab initio data with large-scale lattice Monte-Carlo simulations, we predict several low-energy intermetallic compounds that are expected to dominate alloy microstructures, and hence the low-temperature phase diagrams, for both alloys. Using the predicted ground-state atomic alloy configurations, we investigate the short-range order, point defect (vacancy and self-interstitial atoms) energies, and thermodynamic and mechanical properties of W alloys as functions of their chemical composition. In particular, we evaluate the anisotropic Young modulus for W-Ta and W-V alloys from ab initio elastic constant calculations, with the objective of comparing the predicted values with experimental micro-cantilever measurements. Also, using the calculated Poisson ratios for binary W alloys, which combine tungsten with more than 40 different alloying elements, we investigate if alloying improves the ductility of tungsten-based materials.
-
cluster expansion models for fe cr alloys the prototype materials for a Fusion Power Plant
Computational Materials Science, 2010Co-Authors: Yu M Lavrentiev, D Nguyenmanh, S L DudarevAbstract:Abstract We compare two approaches to modelling the phase stability of iron and Fe–Cr binary alloys: Cluster expansion and magnetic cluster expansion. The first, based on a cluster expansion Hamiltonian, describes the effects of configurational disorder in an alloy on its thermodynamic properties. Cluster expansion can be used for studying alloys by both equilibrium and kinetic Monte Carlo methods. The second, recently proposed, “magnetic” cluster expansion (MCE) method extends cluster expansion treatment to magnetic degrees of freedom by including magnetic moments of individual atoms as variables. MCE has a unique capability for modelling the properties of a magnetic alloy in a broad range of compositions ranging from pure ferromagnetic Fe to antiferromagnetic Cr. We describe applications of both methods to modelling various properties of candidate Fusion materials.
-
implications of Fusion Power Plant studies for materials requirements
Plasma Physics and Controlled Fusion, 2002Co-Authors: I Cook, D J Ward, S L DudarevAbstract:This paper addresses the key requirements for Fusion materials, as these have emerged from studies of commercial Fusion Power Plants. The objective of the international Fusion programme is the creation of Power stations that will have very attractive safety and environmental features and viable economics. Fusion Power Plant studies have shown that these objectives may be achieved without requiring extreme advances in materials. But it is required that existing candidate materials perform at least as well as envisaged in the environment of Fusion neutrons, heat fluxes and particle fluxes. The development of advanced materials would bring further benefits. The work required entails the investigation of many intellectually exciting physics issues of great scientific interest, and of wider application than Fusion. In addition to giving an overview, selected aspects of the science, of particular physics interest, are illustrated.
A Litnovsky - One of the best experts on this subject based on the ideXlab platform.
-
smart first wall materials for intrinsic safety of a Fusion Power Plant
Fusion Engineering and Design, 2018Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, Arkadi Kreter, M Rasinski, J Schmitz, Thomas Wegener, M R Gilbert, X TanAbstract:Abstract The first wall armor of a DEMOnstration Fusion Power Plant (DEMO) is planned to be built from tungsten. However, in case of loss-of-coolant accident with air ingress, the temperature of the first wall may exceed 1000 °C due to nuclear decay heat. At such temperatures, tungsten forms volatile radioactive oxides, which may be mobilized into the environment at a rate of 10–600 kg per hour. Advanced “smart” tungsten alloys adjust their properties to the environment: during the plasma operation, preferential sputtering will form almost pure tungsten surface facing the plasma. In case of an accident, the remaining alloying elements form a protective layer, preventing tungsten mobilization. The new smart alloys contain tungsten (W), chromium (Cr) and yttrium (Y). The first bulk smart alloys produced using field-assisted sintering technique, revealed excellent oxidation resistance for a timescale of 10–20 hours. W-Cr-Y systems underwent combined plasma and oxidation test. During plasma exposure, smart alloys demonstrated nearly the same mass loss as the reference pure tungsten samples. Subsequent oxidation confirmed superior oxidation resistance of new alloys compared to the former W-Cr-Ti systems. Experiments attaining oxidation times and plasma fluence required for DEMO, are started. First results show necessity in further improvement of W-Cr-Y alloys.
-
smart alloys for a future Fusion Power Plant first studies under stationary plasma load and in accidental conditions
Nuclear materials and energy, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, B. Unterberg, Arkadi Kreter, M Rasinski, Thomas Wegener, M Vogel, S Kraus, U BreuerAbstract:Abstract In case of an accident in the future Fusion Power Plant like DEMO, the loss-of-coolant may happen simultaneously with air ingress into the vacuum vessel. The radioactive tungsten and its isotopes from the first wall may become oxidized and vaporized into the environment. The so-called “smart” alloys are under development to suppress the mobilization of oxidized tungsten. Smart alloys are aimed at adjusting their properties to environment. During regular operation, the preferential sputtering of alloying elements by plasma ions should leave almost pure tungsten surface facing the plasma. Under accidental conditions, the alloying elements in the bulk will form an oxide layer protecting tungsten from mobilization. The first direct comparative test of pure tungsten and smart alloys under identical plasma conditions was performed. Tungsten–chromium–titanium alloys were exposed simultaneously with tungsten samples to stationary deuterium plasma in linear plasma device PSI-2. The ion energy and the temperature of samples corresponded well the conditions at the first wall in DEMO. The accumulated fluence was 1.3 × 1026 ion/m2. The weight loss of pure tungsten samples after exposure was ΔmW = 1000–1150 µg. The measured weight loss of sputtered smart alloy sample ΔmSA = 1240µg corresponds very well to that of pure tungsten providing experimental evidence of good resistance of smart alloys to plasma sputtering. Plasma exposure was followed by the oxidation of alloys at 1000 °C accomplishing the first test of these new materials both in a plasma environment and under accidental conditions. Compared to pure tungsten, smart alloys featured the 3-fold suppression of oxidation. Plasma exposure did not affect the oxidation resistance of smart alloys. At the same time, the self-passivation of the protective layer did not occur, calling for further optimization of alloys.
-
advanced smart tungsten alloys for a future Fusion Power Plant
Plasma Physics and Controlled Fusion, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, Arkadi Kreter, J. W. E. Coenen, M Rasinski, J Schmitz, Martin Bram, Thomas Wegener, Jesus GonzalezjulianAbstract:The severe particle, radiation and neutron environment in a future Fusion Power Plant requires the development of advanced plasma-facing materials. At the same time, the highest level of safety needs to be ensured. The so-called loss-of-coolant accident combined with air ingress in the vacuum vessel represents a severe safety challenge. In the absence of a coolant the temperature of the tungsten first wall may reach 1200 °C. At such a temperature, the neutron-activated radioactive tungsten forms volatile oxide which can be mobilized into atmosphere. Smart tungsten alloys are being developed to address this safety issue. Smart alloys should combine an acceptable plasma performance with the suppressed oxidation during an accident. New thin film tungsten–chromium–yttrium smart alloys feature an impressive 105 fold suppression of oxidation compared to that of pure tungsten at temperatures of up to 1000 °C. Oxidation behavior at temperatures up to 1200 °C, and reactivity of alloys in humid atmosphere along with a manufacturing of reactor-relevant bulk samples, impose an additional challenge in smart alloy development. First exposures of smart alloys in steady-state deuterium plasma were made. Smart tungsten–chroimium–titanium alloys demonstrated a sputtering resistance which is similar to that of pure tungsten. Expected preferential sputtering of alloying elements by plasma ions was confirmed experimentally. The subsequent isothermal oxidation of exposed samples did not reveal any influence of plasma exposure on the passivation of alloys.
-
Smart tungsten alloys as a material for the first wall of a future Fusion Power Plant
Nuclear Fusion, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, B. Unterberg, Arkadi Kreter, J. W. E. Coenen, M Rasinski, H Du, Thomas Wegener, J. MayerAbstract:Tungsten is currently deemed as a promising plasma-facing material (PFM) for the future Power Plant DEMO. In the case of an accident, air can get into contact with PFMs during the air ingress. The temperature of PFMs can rise up to 1200 °C due to nuclear decay heat in the case of damaged coolant supply. Heated neutron-activated tungsten forms a volatile radioactive oxide which can be mobilized into the atmosphere. New self-passivating ‘smart’ alloys can adjust their properties to the environment. During plasma operation the preferential sputtering of lighter alloying elements will leave an almost pure tungsten surface facing the plasma. During an accident the alloying elements in the bulk are forming oxides thus protecting tungsten from mobilization. Good plasma performance and the suppression of oxidation are required for smart alloys. Bulk tungsten (W)–chroimum (Cr)–titanium (Ti) alloys were exposed together with pure tungsten (W) samples to the steady-state deuterium plasma under identical conditions in the linear plasma device PSI 2. The temperature of the samples was ~576 °C–715 °C, the energy of impinging ions was 210 eV matching well the conditions expected at the first wall of DEMO. Weight loss measurements demonstrated similar mass decrease of smart alloys and pure tungsten samples. The oxidation of exposed samples has proven no effect of plasma exposure on the oxidation resistance. The W–Cr–Ti alloy demonstrated advantageous 3-fold lower mass gain due to oxidation than that of pure tungsten. New yttrium (Y)-containing thin film systems are demonstrating superior performance in comparison to that of W–Cr–Ti systems and of pure W. The oxidation rate constant of W–Cr–Y thin film is 10 5 times less than that of pure tungsten. However, the detected reactivity of the bulk smart alloy in humid atmosphere is calling for a further improvement.
Ch Linsmeier - One of the best experts on this subject based on the ideXlab platform.
-
smart first wall materials for intrinsic safety of a Fusion Power Plant
Fusion Engineering and Design, 2018Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, Arkadi Kreter, M Rasinski, J Schmitz, Thomas Wegener, M R Gilbert, X TanAbstract:Abstract The first wall armor of a DEMOnstration Fusion Power Plant (DEMO) is planned to be built from tungsten. However, in case of loss-of-coolant accident with air ingress, the temperature of the first wall may exceed 1000 °C due to nuclear decay heat. At such temperatures, tungsten forms volatile radioactive oxides, which may be mobilized into the environment at a rate of 10–600 kg per hour. Advanced “smart” tungsten alloys adjust their properties to the environment: during the plasma operation, preferential sputtering will form almost pure tungsten surface facing the plasma. In case of an accident, the remaining alloying elements form a protective layer, preventing tungsten mobilization. The new smart alloys contain tungsten (W), chromium (Cr) and yttrium (Y). The first bulk smart alloys produced using field-assisted sintering technique, revealed excellent oxidation resistance for a timescale of 10–20 hours. W-Cr-Y systems underwent combined plasma and oxidation test. During plasma exposure, smart alloys demonstrated nearly the same mass loss as the reference pure tungsten samples. Subsequent oxidation confirmed superior oxidation resistance of new alloys compared to the former W-Cr-Ti systems. Experiments attaining oxidation times and plasma fluence required for DEMO, are started. First results show necessity in further improvement of W-Cr-Y alloys.
-
smart alloys for a future Fusion Power Plant first studies under stationary plasma load and in accidental conditions
Nuclear materials and energy, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, B. Unterberg, Arkadi Kreter, M Rasinski, Thomas Wegener, M Vogel, S Kraus, U BreuerAbstract:Abstract In case of an accident in the future Fusion Power Plant like DEMO, the loss-of-coolant may happen simultaneously with air ingress into the vacuum vessel. The radioactive tungsten and its isotopes from the first wall may become oxidized and vaporized into the environment. The so-called “smart” alloys are under development to suppress the mobilization of oxidized tungsten. Smart alloys are aimed at adjusting their properties to environment. During regular operation, the preferential sputtering of alloying elements by plasma ions should leave almost pure tungsten surface facing the plasma. Under accidental conditions, the alloying elements in the bulk will form an oxide layer protecting tungsten from mobilization. The first direct comparative test of pure tungsten and smart alloys under identical plasma conditions was performed. Tungsten–chromium–titanium alloys were exposed simultaneously with tungsten samples to stationary deuterium plasma in linear plasma device PSI-2. The ion energy and the temperature of samples corresponded well the conditions at the first wall in DEMO. The accumulated fluence was 1.3 × 1026 ion/m2. The weight loss of pure tungsten samples after exposure was ΔmW = 1000–1150 µg. The measured weight loss of sputtered smart alloy sample ΔmSA = 1240µg corresponds very well to that of pure tungsten providing experimental evidence of good resistance of smart alloys to plasma sputtering. Plasma exposure was followed by the oxidation of alloys at 1000 °C accomplishing the first test of these new materials both in a plasma environment and under accidental conditions. Compared to pure tungsten, smart alloys featured the 3-fold suppression of oxidation. Plasma exposure did not affect the oxidation resistance of smart alloys. At the same time, the self-passivation of the protective layer did not occur, calling for further optimization of alloys.
-
advanced smart tungsten alloys for a future Fusion Power Plant
Plasma Physics and Controlled Fusion, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, Arkadi Kreter, J. W. E. Coenen, M Rasinski, J Schmitz, Martin Bram, Thomas Wegener, Jesus GonzalezjulianAbstract:The severe particle, radiation and neutron environment in a future Fusion Power Plant requires the development of advanced plasma-facing materials. At the same time, the highest level of safety needs to be ensured. The so-called loss-of-coolant accident combined with air ingress in the vacuum vessel represents a severe safety challenge. In the absence of a coolant the temperature of the tungsten first wall may reach 1200 °C. At such a temperature, the neutron-activated radioactive tungsten forms volatile oxide which can be mobilized into atmosphere. Smart tungsten alloys are being developed to address this safety issue. Smart alloys should combine an acceptable plasma performance with the suppressed oxidation during an accident. New thin film tungsten–chromium–yttrium smart alloys feature an impressive 105 fold suppression of oxidation compared to that of pure tungsten at temperatures of up to 1000 °C. Oxidation behavior at temperatures up to 1200 °C, and reactivity of alloys in humid atmosphere along with a manufacturing of reactor-relevant bulk samples, impose an additional challenge in smart alloy development. First exposures of smart alloys in steady-state deuterium plasma were made. Smart tungsten–chroimium–titanium alloys demonstrated a sputtering resistance which is similar to that of pure tungsten. Expected preferential sputtering of alloying elements by plasma ions was confirmed experimentally. The subsequent isothermal oxidation of exposed samples did not reveal any influence of plasma exposure on the passivation of alloys.
-
Smart tungsten alloys as a material for the first wall of a future Fusion Power Plant
Nuclear Fusion, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, B. Unterberg, Arkadi Kreter, J. W. E. Coenen, M Rasinski, H Du, Thomas Wegener, J. MayerAbstract:Tungsten is currently deemed as a promising plasma-facing material (PFM) for the future Power Plant DEMO. In the case of an accident, air can get into contact with PFMs during the air ingress. The temperature of PFMs can rise up to 1200 °C due to nuclear decay heat in the case of damaged coolant supply. Heated neutron-activated tungsten forms a volatile radioactive oxide which can be mobilized into the atmosphere. New self-passivating ‘smart’ alloys can adjust their properties to the environment. During plasma operation the preferential sputtering of lighter alloying elements will leave an almost pure tungsten surface facing the plasma. During an accident the alloying elements in the bulk are forming oxides thus protecting tungsten from mobilization. Good plasma performance and the suppression of oxidation are required for smart alloys. Bulk tungsten (W)–chroimum (Cr)–titanium (Ti) alloys were exposed together with pure tungsten (W) samples to the steady-state deuterium plasma under identical conditions in the linear plasma device PSI 2. The temperature of the samples was ~576 °C–715 °C, the energy of impinging ions was 210 eV matching well the conditions expected at the first wall of DEMO. Weight loss measurements demonstrated similar mass decrease of smart alloys and pure tungsten samples. The oxidation of exposed samples has proven no effect of plasma exposure on the oxidation resistance. The W–Cr–Ti alloy demonstrated advantageous 3-fold lower mass gain due to oxidation than that of pure tungsten. New yttrium (Y)-containing thin film systems are demonstrating superior performance in comparison to that of W–Cr–Ti systems and of pure W. The oxidation rate constant of W–Cr–Y thin film is 10 5 times less than that of pure tungsten. However, the detected reactivity of the bulk smart alloy in humid atmosphere is calling for a further improvement.
Franziska Klein - One of the best experts on this subject based on the ideXlab platform.
-
smart first wall materials for intrinsic safety of a Fusion Power Plant
Fusion Engineering and Design, 2018Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, Arkadi Kreter, M Rasinski, J Schmitz, Thomas Wegener, M R Gilbert, X TanAbstract:Abstract The first wall armor of a DEMOnstration Fusion Power Plant (DEMO) is planned to be built from tungsten. However, in case of loss-of-coolant accident with air ingress, the temperature of the first wall may exceed 1000 °C due to nuclear decay heat. At such temperatures, tungsten forms volatile radioactive oxides, which may be mobilized into the environment at a rate of 10–600 kg per hour. Advanced “smart” tungsten alloys adjust their properties to the environment: during the plasma operation, preferential sputtering will form almost pure tungsten surface facing the plasma. In case of an accident, the remaining alloying elements form a protective layer, preventing tungsten mobilization. The new smart alloys contain tungsten (W), chromium (Cr) and yttrium (Y). The first bulk smart alloys produced using field-assisted sintering technique, revealed excellent oxidation resistance for a timescale of 10–20 hours. W-Cr-Y systems underwent combined plasma and oxidation test. During plasma exposure, smart alloys demonstrated nearly the same mass loss as the reference pure tungsten samples. Subsequent oxidation confirmed superior oxidation resistance of new alloys compared to the former W-Cr-Ti systems. Experiments attaining oxidation times and plasma fluence required for DEMO, are started. First results show necessity in further improvement of W-Cr-Y alloys.
-
smart alloys for a future Fusion Power Plant first studies under stationary plasma load and in accidental conditions
Nuclear materials and energy, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, B. Unterberg, Arkadi Kreter, M Rasinski, Thomas Wegener, M Vogel, S Kraus, U BreuerAbstract:Abstract In case of an accident in the future Fusion Power Plant like DEMO, the loss-of-coolant may happen simultaneously with air ingress into the vacuum vessel. The radioactive tungsten and its isotopes from the first wall may become oxidized and vaporized into the environment. The so-called “smart” alloys are under development to suppress the mobilization of oxidized tungsten. Smart alloys are aimed at adjusting their properties to environment. During regular operation, the preferential sputtering of alloying elements by plasma ions should leave almost pure tungsten surface facing the plasma. Under accidental conditions, the alloying elements in the bulk will form an oxide layer protecting tungsten from mobilization. The first direct comparative test of pure tungsten and smart alloys under identical plasma conditions was performed. Tungsten–chromium–titanium alloys were exposed simultaneously with tungsten samples to stationary deuterium plasma in linear plasma device PSI-2. The ion energy and the temperature of samples corresponded well the conditions at the first wall in DEMO. The accumulated fluence was 1.3 × 1026 ion/m2. The weight loss of pure tungsten samples after exposure was ΔmW = 1000–1150 µg. The measured weight loss of sputtered smart alloy sample ΔmSA = 1240µg corresponds very well to that of pure tungsten providing experimental evidence of good resistance of smart alloys to plasma sputtering. Plasma exposure was followed by the oxidation of alloys at 1000 °C accomplishing the first test of these new materials both in a plasma environment and under accidental conditions. Compared to pure tungsten, smart alloys featured the 3-fold suppression of oxidation. Plasma exposure did not affect the oxidation resistance of smart alloys. At the same time, the self-passivation of the protective layer did not occur, calling for further optimization of alloys.
-
advanced smart tungsten alloys for a future Fusion Power Plant
Plasma Physics and Controlled Fusion, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, Arkadi Kreter, J. W. E. Coenen, M Rasinski, J Schmitz, Martin Bram, Thomas Wegener, Jesus GonzalezjulianAbstract:The severe particle, radiation and neutron environment in a future Fusion Power Plant requires the development of advanced plasma-facing materials. At the same time, the highest level of safety needs to be ensured. The so-called loss-of-coolant accident combined with air ingress in the vacuum vessel represents a severe safety challenge. In the absence of a coolant the temperature of the tungsten first wall may reach 1200 °C. At such a temperature, the neutron-activated radioactive tungsten forms volatile oxide which can be mobilized into atmosphere. Smart tungsten alloys are being developed to address this safety issue. Smart alloys should combine an acceptable plasma performance with the suppressed oxidation during an accident. New thin film tungsten–chromium–yttrium smart alloys feature an impressive 105 fold suppression of oxidation compared to that of pure tungsten at temperatures of up to 1000 °C. Oxidation behavior at temperatures up to 1200 °C, and reactivity of alloys in humid atmosphere along with a manufacturing of reactor-relevant bulk samples, impose an additional challenge in smart alloy development. First exposures of smart alloys in steady-state deuterium plasma were made. Smart tungsten–chroimium–titanium alloys demonstrated a sputtering resistance which is similar to that of pure tungsten. Expected preferential sputtering of alloying elements by plasma ions was confirmed experimentally. The subsequent isothermal oxidation of exposed samples did not reveal any influence of plasma exposure on the passivation of alloys.
-
Smart tungsten alloys as a material for the first wall of a future Fusion Power Plant
Nuclear Fusion, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, B. Unterberg, Arkadi Kreter, J. W. E. Coenen, M Rasinski, H Du, Thomas Wegener, J. MayerAbstract:Tungsten is currently deemed as a promising plasma-facing material (PFM) for the future Power Plant DEMO. In the case of an accident, air can get into contact with PFMs during the air ingress. The temperature of PFMs can rise up to 1200 °C due to nuclear decay heat in the case of damaged coolant supply. Heated neutron-activated tungsten forms a volatile radioactive oxide which can be mobilized into the atmosphere. New self-passivating ‘smart’ alloys can adjust their properties to the environment. During plasma operation the preferential sputtering of lighter alloying elements will leave an almost pure tungsten surface facing the plasma. During an accident the alloying elements in the bulk are forming oxides thus protecting tungsten from mobilization. Good plasma performance and the suppression of oxidation are required for smart alloys. Bulk tungsten (W)–chroimum (Cr)–titanium (Ti) alloys were exposed together with pure tungsten (W) samples to the steady-state deuterium plasma under identical conditions in the linear plasma device PSI 2. The temperature of the samples was ~576 °C–715 °C, the energy of impinging ions was 210 eV matching well the conditions expected at the first wall of DEMO. Weight loss measurements demonstrated similar mass decrease of smart alloys and pure tungsten samples. The oxidation of exposed samples has proven no effect of plasma exposure on the oxidation resistance. The W–Cr–Ti alloy demonstrated advantageous 3-fold lower mass gain due to oxidation than that of pure tungsten. New yttrium (Y)-containing thin film systems are demonstrating superior performance in comparison to that of W–Cr–Ti systems and of pure W. The oxidation rate constant of W–Cr–Y thin film is 10 5 times less than that of pure tungsten. However, the detected reactivity of the bulk smart alloy in humid atmosphere is calling for a further improvement.
Arkadi Kreter - One of the best experts on this subject based on the ideXlab platform.
-
smart first wall materials for intrinsic safety of a Fusion Power Plant
Fusion Engineering and Design, 2018Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, Arkadi Kreter, M Rasinski, J Schmitz, Thomas Wegener, M R Gilbert, X TanAbstract:Abstract The first wall armor of a DEMOnstration Fusion Power Plant (DEMO) is planned to be built from tungsten. However, in case of loss-of-coolant accident with air ingress, the temperature of the first wall may exceed 1000 °C due to nuclear decay heat. At such temperatures, tungsten forms volatile radioactive oxides, which may be mobilized into the environment at a rate of 10–600 kg per hour. Advanced “smart” tungsten alloys adjust their properties to the environment: during the plasma operation, preferential sputtering will form almost pure tungsten surface facing the plasma. In case of an accident, the remaining alloying elements form a protective layer, preventing tungsten mobilization. The new smart alloys contain tungsten (W), chromium (Cr) and yttrium (Y). The first bulk smart alloys produced using field-assisted sintering technique, revealed excellent oxidation resistance for a timescale of 10–20 hours. W-Cr-Y systems underwent combined plasma and oxidation test. During plasma exposure, smart alloys demonstrated nearly the same mass loss as the reference pure tungsten samples. Subsequent oxidation confirmed superior oxidation resistance of new alloys compared to the former W-Cr-Ti systems. Experiments attaining oxidation times and plasma fluence required for DEMO, are started. First results show necessity in further improvement of W-Cr-Y alloys.
-
smart alloys for a future Fusion Power Plant first studies under stationary plasma load and in accidental conditions
Nuclear materials and energy, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, B. Unterberg, Arkadi Kreter, M Rasinski, Thomas Wegener, M Vogel, S Kraus, U BreuerAbstract:Abstract In case of an accident in the future Fusion Power Plant like DEMO, the loss-of-coolant may happen simultaneously with air ingress into the vacuum vessel. The radioactive tungsten and its isotopes from the first wall may become oxidized and vaporized into the environment. The so-called “smart” alloys are under development to suppress the mobilization of oxidized tungsten. Smart alloys are aimed at adjusting their properties to environment. During regular operation, the preferential sputtering of alloying elements by plasma ions should leave almost pure tungsten surface facing the plasma. Under accidental conditions, the alloying elements in the bulk will form an oxide layer protecting tungsten from mobilization. The first direct comparative test of pure tungsten and smart alloys under identical plasma conditions was performed. Tungsten–chromium–titanium alloys were exposed simultaneously with tungsten samples to stationary deuterium plasma in linear plasma device PSI-2. The ion energy and the temperature of samples corresponded well the conditions at the first wall in DEMO. The accumulated fluence was 1.3 × 1026 ion/m2. The weight loss of pure tungsten samples after exposure was ΔmW = 1000–1150 µg. The measured weight loss of sputtered smart alloy sample ΔmSA = 1240µg corresponds very well to that of pure tungsten providing experimental evidence of good resistance of smart alloys to plasma sputtering. Plasma exposure was followed by the oxidation of alloys at 1000 °C accomplishing the first test of these new materials both in a plasma environment and under accidental conditions. Compared to pure tungsten, smart alloys featured the 3-fold suppression of oxidation. Plasma exposure did not affect the oxidation resistance of smart alloys. At the same time, the self-passivation of the protective layer did not occur, calling for further optimization of alloys.
-
advanced smart tungsten alloys for a future Fusion Power Plant
Plasma Physics and Controlled Fusion, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, Arkadi Kreter, J. W. E. Coenen, M Rasinski, J Schmitz, Martin Bram, Thomas Wegener, Jesus GonzalezjulianAbstract:The severe particle, radiation and neutron environment in a future Fusion Power Plant requires the development of advanced plasma-facing materials. At the same time, the highest level of safety needs to be ensured. The so-called loss-of-coolant accident combined with air ingress in the vacuum vessel represents a severe safety challenge. In the absence of a coolant the temperature of the tungsten first wall may reach 1200 °C. At such a temperature, the neutron-activated radioactive tungsten forms volatile oxide which can be mobilized into atmosphere. Smart tungsten alloys are being developed to address this safety issue. Smart alloys should combine an acceptable plasma performance with the suppressed oxidation during an accident. New thin film tungsten–chromium–yttrium smart alloys feature an impressive 105 fold suppression of oxidation compared to that of pure tungsten at temperatures of up to 1000 °C. Oxidation behavior at temperatures up to 1200 °C, and reactivity of alloys in humid atmosphere along with a manufacturing of reactor-relevant bulk samples, impose an additional challenge in smart alloy development. First exposures of smart alloys in steady-state deuterium plasma were made. Smart tungsten–chroimium–titanium alloys demonstrated a sputtering resistance which is similar to that of pure tungsten. Expected preferential sputtering of alloying elements by plasma ions was confirmed experimentally. The subsequent isothermal oxidation of exposed samples did not reveal any influence of plasma exposure on the passivation of alloys.
-
Smart tungsten alloys as a material for the first wall of a future Fusion Power Plant
Nuclear Fusion, 2017Co-Authors: A Litnovsky, Ch Linsmeier, Franziska Klein, B. Unterberg, Arkadi Kreter, J. W. E. Coenen, M Rasinski, H Du, Thomas Wegener, J. MayerAbstract:Tungsten is currently deemed as a promising plasma-facing material (PFM) for the future Power Plant DEMO. In the case of an accident, air can get into contact with PFMs during the air ingress. The temperature of PFMs can rise up to 1200 °C due to nuclear decay heat in the case of damaged coolant supply. Heated neutron-activated tungsten forms a volatile radioactive oxide which can be mobilized into the atmosphere. New self-passivating ‘smart’ alloys can adjust their properties to the environment. During plasma operation the preferential sputtering of lighter alloying elements will leave an almost pure tungsten surface facing the plasma. During an accident the alloying elements in the bulk are forming oxides thus protecting tungsten from mobilization. Good plasma performance and the suppression of oxidation are required for smart alloys. Bulk tungsten (W)–chroimum (Cr)–titanium (Ti) alloys were exposed together with pure tungsten (W) samples to the steady-state deuterium plasma under identical conditions in the linear plasma device PSI 2. The temperature of the samples was ~576 °C–715 °C, the energy of impinging ions was 210 eV matching well the conditions expected at the first wall of DEMO. Weight loss measurements demonstrated similar mass decrease of smart alloys and pure tungsten samples. The oxidation of exposed samples has proven no effect of plasma exposure on the oxidation resistance. The W–Cr–Ti alloy demonstrated advantageous 3-fold lower mass gain due to oxidation than that of pure tungsten. New yttrium (Y)-containing thin film systems are demonstrating superior performance in comparison to that of W–Cr–Ti systems and of pure W. The oxidation rate constant of W–Cr–Y thin film is 10 5 times less than that of pure tungsten. However, the detected reactivity of the bulk smart alloy in humid atmosphere is calling for a further improvement.
