Projects / Programmes
Effect of deuterium on lattice defect saturation in tungsten
| Code |
Science |
Field |
Subfield |
| 1.02.00 |
Natural sciences and mathematics |
Physics |
|
| Code |
Science |
Field |
| P002 |
Natural sciences and mathematics |
Physics |
| Code |
Science |
Field |
| 1.03 |
Natural Sciences |
Physical sciences |
deuterium retention, damaged tungsten, damage saturation in tungsten
Researchers (1)
| no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
| 1. |
35487 |
PhD Anže Založnik |
Physics |
Head |
2018 |
47 |
Organisations (1)
| no. |
Code |
Research organisation |
City |
Registration number |
No. of publicationsNo. of publications |
| 1. |
0106 |
Jožef Stefan Institute |
Ljubljana |
5051606000 |
90,664 |
Abstract
On our way to exploiting nuclear fusion as an almost unlimited source of green energy, some barriers still have to be overcome. One of these barriers is fusion fuel retention in the walls of a fusion device, which represents an economical and safety issue. We have to be able to estimate fuel retention in the walls with a high precision in order to efficiently develop and perform fuel recovery protocols.
Fuel retention in the bulk of the wall material is enhanced by neutron irradiation defects. According to previous studies these defects saturate at certain saturation level in pristine tungsten. However, a presence of deuterium in the bulk during the damaging procedure resulted in defect concentrations larger than the saturation limit for the pristine sample. Since deuterium will be present at all times during the operation of a fusion device, a deep understanding of this phenomenon is necessary in order to improve our prediction accuracy for fuel retention.
The proposed study will focus on the dynamics of defect evolution in damaged tungsten and its dependency on the presence of deuterium in the bulk. Pre-damaged tungsten samples will be exposed to various flux densities of deuterium, resulting in different deuterium concentrations in the bulk. After that the samples will be additionally damaged and loaded with low energy deuterium atoms to populate the additionally created defects. Deuterium concentration and total amount in the samples will be measured by two techniques: nuclear reaction analysis and thermal desorption spectroscopy. Since deuterium concentration can be a measure of defect concentration, new damage saturation limits will be obtained as a function of initial deuterium concentration in the bulk. Moreover, since thermal desorption spectroscopy allows us to distinguish between different defect types in the crystal lattice, we can determine the saturation limit for each defect type separately. Most of the experimental procedure will be conducted in-situ, without taking the samples out of vacuum conditions, avoiding exposure to air and other impurities. Experimental results will be implemented in the new, improved model, which will be used for estimating deuterium retention in tungsten.
Significance for science
The proposed study will provide an in-depth understanding on the influence of D concentration in the material on W lattice defect dynamics. The obtained results will explain the phenomena observed in the study by Markelj et al., Nucl. Mater. Energy 12 (2017) which was the first study of simultaneous W damaging and D atom exposure. The results of the proposed study will provide data on W lattice defect saturation dependence on D concentration in the material which has never been measured before. Moreover, the obtained data will enable us to distinguish and separate the dynamics of different defect types, following the influence of D concentration on individual defect types and determining the differences in their dynamics.
The results of this study will be of great importance for the estimation of the fusion fuel retention in the wall of a fusion device. Hydrogen isotope retention has been extensively studied in pre-damaged W material, however such studies do not resemble the real condition inside a working fusion device. During the operation the wall material will be simultaneously damaged and exposed to hydrogen isotopes which will change the lattice defect creation and annihilation dynamics. Therefore, this study will provide important data on the lattice defect saturation dependence on D concentration in the bulk of the material. These results will be implemented in the new and improved models which will simulate the real conditions inside an operating fusion device and accurately estimate the damage level of the PFC and fusion fuel retention in the wall of the device.
Significance for the country
The proposed study will provide an in-depth understanding on the influence of D concentration in the material on W lattice defect dynamics. The obtained results will explain the phenomena observed in the study by Markelj et al., Nucl. Mater. Energy 12 (2017) which was the first study of simultaneous W damaging and D atom exposure. The results of the proposed study will provide data on W lattice defect saturation dependence on D concentration in the material which has never been measured before. Moreover, the obtained data will enable us to distinguish and separate the dynamics of different defect types, following the influence of D concentration on individual defect types and determining the differences in their dynamics.
The results of this study will be of great importance for the estimation of the fusion fuel retention in the wall of a fusion device. Hydrogen isotope retention has been extensively studied in pre-damaged W material, however such studies do not resemble the real condition inside a working fusion device. During the operation the wall material will be simultaneously damaged and exposed to hydrogen isotopes which will change the lattice defect creation and annihilation dynamics. Therefore, this study will provide important data on the lattice defect saturation dependence on D concentration in the bulk of the material. These results will be implemented in the new and improved models which will simulate the real conditions inside an operating fusion device and accurately estimate the damage level of the PFC and fusion fuel retention in the wall of the device.
