Abstract
Materials exposed to plasmas in magnetic confinement nuclear reactors will accumulate radiation-induced defects and energetically implanted gas atoms (from the plasma and transmutations), of which insoluble helium (He) is likely to be the most problematic. The large surface-area-to-volume ratio exhibited by nanoporous materials provides an unsaturable sink with the potential to continuously remove both point defects and He. This property enhances the possibilities for these materials to be tailored for high radiation-damage resistance. In order to explore the potential effect of this on the individual ligaments of nanoporous materials, we present results on the response of tungsten (W) nanoparticles (NPs) to 15 keV He ion irradiation. Tungsten foils and various sizes of NPs were ion irradiated concurrently and imaged in-situ via transmission electron microscopy at 750 °C. Helium bubbles were not observed in NPs with diameters less than 20 nm but did form in larger NPs and the foils. No dislocation loops or black spot damage were observed in any NPs up to 100 nm in diameter but were found to accumulate in the W foils. These results indicate that a nanoporous material, particularly one made up of ligaments with characteristic dimensions of 30 nm or less, is likely to exhibit significant resistance to He accumulation and structural damage and, therefore, be highly tolerant to radiation.
Highlights
The prospect of using nuclear fusion for energy production has motivated a large research effort with the aim of finding suitable materials to be used for fusion reactors [1]
ITER, currently under construction, is a thermonuclear project that will demonstrate the use of magnetic confinement to sustain a plasma of sufficiently high temperature to induce the fusion of deuterium and tritium for significantly longer periods and on a larger scale than in previous reactors such as the Joint European Torus (JET) and Toroidal Fusion Test Reactors (TFTR) [1,2]
During ion irradiation as a means to simulate reactor conditions, the incident particles interact with the atoms of the target material creating displaced atoms which can aggregate in the form of point defect clusters that can grow to form extended defects such as dislocation loops [10,11]
Summary
The prospect of using nuclear fusion for energy production has motivated a large research effort with the aim of finding suitable materials to be used for fusion reactors [1]. ITER, currently under construction, is a thermonuclear project that will demonstrate the use of magnetic confinement to sustain a plasma of sufficiently high temperature to induce the fusion of deuterium and tritium for significantly longer periods and on a larger scale than in previous reactors such as the Joint European Torus (JET) and Toroidal Fusion Test Reactors (TFTR) [1,2] Such reactors will be designed to contain the plasma as much as possible, the surrounding materials are still expected to encounter extreme conditions of high irradiation fluxes and large heat loads in the range of 8–10 MW·m−2 [3,4]. Misra et al [17] induced ultra-high strengths and enhanced radiation tolerance by decreasing the diffusion length to the nearest sink via tailoring the layer thickness in nanolayered Cu-Nb composites
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