Mechanical Testing of Nuclear Materials in Small Length Scales

Dear Colleagues,

The ever-increasing global demand for energy and the urgency of reducing greenhouse gases to prevent global warming has catalyzed a renewed search for clean, viable, safe and sustainable energy sources. Nuclear reactors provide an attractive alternative to fossil fuels in meeting these challenges.  New reactors are being designed to increase efficiency, reduce radioactive wastes, and improve safety of operation. However, such nuclear applications usually entail a combination of different extreme conditions, such as high temperatures, high radiation doses, and corrosive environments. The combination of these multiple harsh environments poses a challenge in some cases, and they require the use of materials which can withstand such extreme environments.

As such, the newly designed materials, as well as the currently used ones, need to be tested for changes in their mechanical properties under these harsh conditions. In recent years, small-scale mechanical testing techniques, such as nanoindentation, micro compression testing, micro-tensile testing and others have become increasingly popular in the nuclear materials community for several reasons. Firstly, ion irradiation is being increasingly used as an alternative method of simulating radiation damage in materials, reducing the duration of the radiation experiments by many orders of magnitude. Small-scale testing allows one to assess the mechanical properties of ion-irradiated materials which otherwise would not be accessible due to limited beam penetration.  Secondly, in the case of neutron irradiation, it reduces the amount of active material that one must handle due to reduced sample size. Thirdly, it allows one to target specific microstructural regions of interest, be they individual grain boundaries, oxide layers or phases and orientations.

In recent years, the development of newer technologies has prompted a wave of devices which can perform various types of tests, such as nanoindentation, compression, tension, bending, etc., at the sub-micron to sub-millimetre scale. However, there are many outstanding issues—such as grain and sample size, strain rate, temperature, etc.—which affect the results and demand proper analysis, in order for the application of these methods to engineer problems to be possible.

The subjects relevant to these and related questions, which the present issue aims to cover, are suggested in (but not limited to) the following list:

• Technique development for nanoindentation, micromechanical testing, in situ imaging, etc.
• Results of nanoindentation or other micromechanical testing on irradiated or unirradiated materials relevant to nuclear or space applications
• Numerical (finite element, crystal plasticity, dislocation dynamics, molecular dynamics or other methods) and analytical (plasticity-based models, etc.) modelling of small-scale testing
• Characterization of nuclear/space relevant materials tested at the small scale
• Expanding small-scale mechanical testing to non-ambient condition.

The editors solicit papers with original research or review papers in these and related topics for publication in this Special Issue on “Mechanical Testing of Nuclear Materials in Small Length Scales”.

Dr. Dhriti Bhattacharyya
Prof. Dr. Peter Hosemann
Guest Editors

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• micromechanical testing
• nanoindentation
• nuclear materials
• radiation damage
• mechanical properties
• in situ testing
• characterization
• modelling