NSUF 23-1854: Ion Irradiation tolerance of Gadolinium titanates / zirconates as candidates for waste form matrices
NSUF RTE Argonne National Labs IVEM – Tandem facility. October 2022 Investigators: Nestor Zaluzec (PI) Robert D. Aughterson
Technical Abstract:
Objectives Gadolinium titanates / zirconates with pyrochlore and fluorite structures have been synthesised and characterised with a focus on creating materials suitable for use as wasteform matrices. The aim of this study is to develop ceramic fabrication techniques and test the radiation tolerance of these matrices. The objective of monitoring the test materials’ response to irradiating ions is to attain a quantifiable characteristic; the critical fluence of irradiating ions required to facilitate a transition from a crystalline to amorphous state, Fc. This provides a means of quantitatively comparing the radiation response between the materials of interest. Also by measuring the Fc at various temperatures and plotting the response we attain a second quantity; the critical temperature of crystallinity, Tc, (the temperature above which the rate of crystalline structure recovery is greater than the rate of defect accumulation). This gives us another means of comparing material response to ion-irradiation along with testing at temperatures applicable to nuclear-based application environments.
Methods A systematic series of gadolinium titanate/zirconate compounds are exposed to high energy ions (Kr 1 MeV) whilst being monitored in situ using the transmission electron microscope (TEM) (IVEM-tandem facility). Collection of bright field images (BF) and electron diffraction patterns (SADP) are used to monitor the crystalline to amorphous phase transition. The TEM specimens consist of either mechanically thinned and ion beam polished specimens or finely ground ceramic crystalline fragments dispersed on holey carbon film supported on TEM specimen grids. TEM characterisation involves monitoring a minimum of 5 electron transparent crystal fragments via the collection of BF and SADPs. After collection of images the sample is irradiated to a certain fluence. Selected ion fluence steps followed by BF and SADP collection are continued until there are no observable Bragg diffraction maxima left in the SADP. This approach is used to quantify the irradiating ion fluence required to cause amorphisation. The critical fluence of amorphisation gives a quantitative approach for comparing radiation response between different test materials. This same experimental approach is repeated for the test material whilst holding it at a range of temperatures. The duration of each critical fluence measurement is dependent on both the fluence of ions required to render the sample amorphous and the time it takes to cool or heat the sample.
Potential Impact to state-of-the Knowledge The proposed test materials have not been previously described in the literature. They have pyrochlore / fluorite structure types, structures associated with flexibility in radionuclide incorporation along with radiation tolerance. The proposed test materials consist of novel compounds that may lend to improvement in these properties. The proposed radiation response study will have considerable impact on the decision making process of the best candidates for further development as wasteform matrices.
Period of performance
On average 1 critical fluence measurement takes approximately 2 hours. 3 to 5 specimens are tested per day. There are 8 samples, each requiring multiple runs. The proposed experiments will require approximately 1 day per sample. This proposal is requesting the maximum 10 days.
Scientific Outcome
Peer reviewed publications, conference presentations.
Additional Info
| Field | Value |
|---|---|
| Abstract | NSUF RTE Argonne National Labs IVEM – Tandem facility. October 2022 Investigators: Nestor Zaluzec (PI) Robert D. Aughterson Technical Abstract: Objectives Gadolinium titanates / zirconates with pyrochlore and fluorite structures have been synthesised and characterised with a focus on creating materials suitable for use as wasteform matrices. The aim of this study is to develop ceramic fabrication techniques and test the radiation tolerance of these matrices. The objective of monitoring the test materials’ response to irradiating ions is to attain a quantifiable characteristic; the critical fluence of irradiating ions required to facilitate a transition from a crystalline to amorphous state, Fc. This provides a means of quantitatively comparing the radiation response between the materials of interest. Also by measuring the Fc at various temperatures and plotting the response we attain a second quantity; the critical temperature of crystallinity, Tc, (the temperature above which the rate of crystalline structure recovery is greater than the rate of defect accumulation). This gives us another means of comparing material response to ion-irradiation along with testing at temperatures applicable to nuclear-based application environments. Methods A systematic series of gadolinium titanate/zirconate compounds are exposed to high energy ions (Kr 1 MeV) whilst being monitored in situ using the transmission electron microscope (TEM) (IVEM-tandem facility). Collection of bright field images (BF) and electron diffraction patterns (SADP) are used to monitor the crystalline to amorphous phase transition. The TEM specimens consist of either mechanically thinned and ion beam polished specimens or finely ground ceramic crystalline fragments dispersed on holey carbon film supported on TEM specimen grids. TEM characterisation involves monitoring a minimum of 5 electron transparent crystal fragments via the collection of BF and SADPs. After collection of images the sample is irradiated to a certain fluence. Selected ion fluence steps followed by BF and SADP collection are continued until there are no observable Bragg diffraction maxima left in the SADP. This approach is used to quantify the irradiating ion fluence required to cause amorphisation. The critical fluence of amorphisation gives a quantitative approach for comparing radiation response between different test materials. This same experimental approach is repeated for the test material whilst holding it at a range of temperatures. The duration of each critical fluence measurement is dependent on both the fluence of ions required to render the sample amorphous and the time it takes to cool or heat the sample. Potential Impact to state-of-the Knowledge The proposed test materials have not been previously described in the literature. They have pyrochlore / fluorite structure types, structures associated with flexibility in radionuclide incorporation along with radiation tolerance. The proposed test materials consist of novel compounds that may lend to improvement in these properties. The proposed radiation response study will have considerable impact on the decision making process of the best candidates for further development as wasteform matrices. Period of performance On average 1 critical fluence measurement takes approximately 2 hours. 3 to 5 specimens are tested per day. There are 8 samples, each requiring multiple runs. The proposed experiments will require approximately 1 day per sample. This proposal is requesting the maximum 10 days. Scientific Outcome Peer reviewed publications, conference presentations. |
| Award Announced Date | 2023-02-08T10:51:06.193 |
| Awarded Institution | None |
| Facility | None |
| Facility Tech Lead | Wei-Ying Chen |
| Irradiation Facility | None |
| PI | Nestor Zaluzec |
| PI Email | [email protected] |
| Project Type | RTE |
| RTE Number | 4529 |