NSUF 19-1634: Bubble formation of in-situ He-implanted 14YWT and CNA advanced nanostructured ferritic alloys
Helium in irradiated materials can cause low-temperature hardening, void swelling, and high-temperature grain boundary embrittlement. These effects can degrade the mechanical performance of structural materials and impact the economics and safety of current or future fission power plants. Recent studies have proposed that these effects could be mitigated by increasing the number of He trapping sites to control the bubble size or to shield He from the grain boundaries. [1][2] This concept have led to the development of high sink strength materials with nanoclusters, such as Oxide dispersion strengthened (ODS) alloys. Cavity size and density of different irradiated nanostructure materials were investigated under ex-situ TEM. [2][3] However, there is no systematic irradiation data showing how the density of nanoclusters in 14TWT and CAN materials affect the helium bubble density and size at elevated temperatures. Therefore, In-situ irradiation experiments are needed to investigate the radiation performance of this material design. In-situ He implantation of samples utilizing the IVEM facility will provide a better understanding of the mechanism of the formation of bubbles in the nanostructured materials and a clearer guideline for applying these materials at specific temperatures. In this proposal, we will conduct in-situ helium implantation on ~70nm TEM foils of 14YWT and CNA3 nanostructured alloys. The 10 KeV He ions with a flux up to 1012 ions/cm2/sec are selected to irradiate the thin TEM foils. Based on our SRIM calculation results, the peak radiation damage and He concentration (at depth 30nm) were estimated to reach 0.3dpa and 5400appm, respectively. Therefore, the total fluence for each implantation experiment will be approximately 5×1015 ions/cm2, which takes around 83 minutes (5000 sec). In total, four samples will be investigated. Using the same He implantation condition, FIB samples of both 14YWT and CNA3 are prepared to be implanted at 500°C, 600°C, and 700°C. For the 500°C experiments, when the peak dose reaches 6000appm, we will stop the implantation and start to increase the temperature to 700°C. These annealing results can be used to compare with the 600°C and 700°C directly hot implanted experiments. Therefore, we require 10 days of facility times of IVEM facility to complete the irradiation and characterization of the proposed experimental conditions. In our previous ex-situ bulk He implantation results, no bubbles were observed in both alloys at 700°C. At high temperature, one possible explanation of this phenomenon may due to the increment of nanocluster surface energy, which could reduce the He trapping ability of these nanoclusters. Utilizing the IVEM Facility, we could study the interaction between helium bubbles and nanoclusters at elevated temperatures. In addition, annealing the He-implanted samples from 500-700°C under in-situ TEM, we could verify the effective temperature of these nanoclusters. Moreover, our previous EELS results showed that bubbles in CNA are attached on the nanoclusters, whereas bubbles seemed to be enclosed in the 14YWT ODS clusters. The IVEM facility could provide videos showing the dynamic evolution of bubble formation and their interaction with nanoclusters in 14YWT and CNA3 will provide direct observation to explain the morphological difference in the bubble-nanocluster complex between the two materials. References[1] S.J. Zinkle, Advanced irradiation-resistant materials for Generation IV nuclear reactors. P. Yvon (Ed.), Structural Materials for Generation IV Nuclear Reactors, Woodhead Publishing Series in Energy (2016), ch.16, pp. 569-594 [2] C.M. Parish et al., Journal of Nuclear Materials 483 (2017) 21-34[3] Y.R. Lin et al., “Bubble formation in helium-implanted nanostructured 14YWT and CNA ferritic alloys at elevated temperatures”, NuMat, 2018, Seattle, USA
추가 정보
| 필드 | 값 |
|---|---|
| Abstract | Helium in irradiated materials can cause low-temperature hardening, void swelling, and high-temperature grain boundary embrittlement. These effects can degrade the mechanical performance of structural materials and impact the economics and safety of current or future fission power plants. Recent studies have proposed that these effects could be mitigated by increasing the number of He trapping sites to control the bubble size or to shield He from the grain boundaries. [1][2] This concept have led to the development of high sink strength materials with nanoclusters, such as Oxide dispersion strengthened (ODS) alloys. Cavity size and density of different irradiated nanostructure materials were investigated under ex-situ TEM. [2][3] However, there is no systematic irradiation data showing how the density of nanoclusters in 14TWT and CAN materials affect the helium bubble density and size at elevated temperatures. Therefore, In-situ irradiation experiments are needed to investigate the radiation performance of this material design. In-situ He implantation of samples utilizing the IVEM facility will provide a better understanding of the mechanism of the formation of bubbles in the nanostructured materials and a clearer guideline for applying these materials at specific temperatures. In this proposal, we will conduct in-situ helium implantation on ~70nm TEM foils of 14YWT and CNA3 nanostructured alloys. The 10 KeV He ions with a flux up to 1012 ions/cm2/sec are selected to irradiate the thin TEM foils. Based on our SRIM calculation results, the peak radiation damage and He concentration (at depth 30nm) were estimated to reach 0.3dpa and 5400appm, respectively. Therefore, the total fluence for each implantation experiment will be approximately 5×1015 ions/cm2, which takes around 83 minutes (5000 sec). In total, four samples will be investigated. Using the same He implantation condition, FIB samples of both 14YWT and CNA3 are prepared to be implanted at 500°C, 600°C, and 700°C. For the 500°C experiments, when the peak dose reaches 6000appm, we will stop the implantation and start to increase the temperature to 700°C. These annealing results can be used to compare with the 600°C and 700°C directly hot implanted experiments. Therefore, we require 10 days of facility times of IVEM facility to complete the irradiation and characterization of the proposed experimental conditions. In our previous ex-situ bulk He implantation results, no bubbles were observed in both alloys at 700°C. At high temperature, one possible explanation of this phenomenon may due to the increment of nanocluster surface energy, which could reduce the He trapping ability of these nanoclusters. Utilizing the IVEM Facility, we could study the interaction between helium bubbles and nanoclusters at elevated temperatures. In addition, annealing the He-implanted samples from 500-700°C under in-situ TEM, we could verify the effective temperature of these nanoclusters. Moreover, our previous EELS results showed that bubbles in CNA are attached on the nanoclusters, whereas bubbles seemed to be enclosed in the 14YWT ODS clusters. The IVEM facility could provide videos showing the dynamic evolution of bubble formation and their interaction with nanoclusters in 14YWT and CNA3 will provide direct observation to explain the morphological difference in the bubble-nanocluster complex between the two materials. References[1] S.J. Zinkle, Advanced irradiation-resistant materials for Generation IV nuclear reactors. P. Yvon (Ed.), Structural Materials for Generation IV Nuclear Reactors, Woodhead Publishing Series in Energy (2016), ch.16, pp. 569-594 [2] C.M. Parish et al., Journal of Nuclear Materials 483 (2017) 21-34[3] Y.R. Lin et al., “Bubble formation in helium-implanted nanostructured 14YWT and CNA ferritic alloys at elevated temperatures”, NuMat, 2018, Seattle, USA |
| Award Announced Date | 2019-02-08T00:00:00 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Wei-Ying Chen |
| Irradiation Facility | None |
| PI | Yan-Ru Lin |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 1634 |