Advanced Characterization and Testing of Nuclear Materials

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: 31 December 2024 | Viewed by 4963

Special Issue Editors


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Guest Editor
Senior Scientist, Institute of Materials Engineering, Australian Nuclear Science and Technology Organization, New Illawarra Road, Lucas Heights, NSW, 2234, Australia
Interests: radiation effects on materials; mechanical behaviour of materials; phase transformations in metallic materials; materials characterization including TEM, SEM, EBSD; in situ nano- and micro- mechanical testing
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Guest Editor
Department of Nuclear Engineering, University of California, Berkeley, 4169 Etcheverry Hall, Berkeley, CA 94720, USA
Interests: materials in extreme environments; structure property relationship; mechanical properties; corrosion
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The ever-increasing global demand for energy and the urgency of reducing greenhouse gases to prevent global warming has catalysed 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 waste, and improve the 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 harsh environments poses considerable challenges, and it requires the use of materials that can withstand such extreme conditions.

As such, the newly designed materials, as well as the currently used ones, need to be tested for changes in their microstructure and mechanical properties after exposure to these harsh conditions. The special nature of the effects of irradiation by energetic particles, including both neutrons and ions, demands the use of advanced characterization and testing techniques to understand the complex changes effected by these processes.

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

Apart from micromechanical testing, it is also imperative to test the materials at a larger scale, as some materials have large grains, which lend themselves better to meso- or mini-scale testing. Such tests can also be used to validate models used to extrapolate test results from the micron scale to the bulk scale. Moreover, when neutron-irradiated materials are tested with the proper safety precautions, they allow full-scale testing, which provides a definitive way to check the engineering properties of irradiated metals and alloys.

In terms of microstructural characterization, a range of advanced techniques are available that facilitate the understanding of the damage phenomena and their underlying processes spanning different length scales. For instance, transmission electron microscopy (TEM) and atom-probe tomography (APT) can be used at the angstrom to ~100 nm scale for obtaining insights into the chemical redistribution of atomic species (through energy dispersive spectroscopy or EDS) and radiation-induced defect structures, voids, bubbles, etc. (through diffraction imaging). At the sub-micron to sub-mm scale, TEM and scanning electron microscopy (SEM), including electron backscatter diffraction (EBSD), can be used to understand the deformation structures and fracture characteristics. In order to obtain statistical information on void or precipitate distributions, diffraction techniques such as small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) techniques are found to be extremely useful.

In light of all these advanced techniques available for the characterization and testing of nuclear materials, authors are invited to send original research papers on subjects including, but not limited to, those suggested in the following list:

  • Technique development for mechanical testing including nanoindentation, micromechanical testing, mini- and meso-scale testing, etc.;
  • Novel methods of characterization of irradiated and un-irradiated nuclear materials at all scales,involving APT, TEM, SEM, EBSD, EDS, SANS, SAXS, confocal microscopy, etc.;
  • New research findings in characterization and testing of nuclear materials in both unirradiated and irradiated conditions at all scales;
  • Numerical (finite element, crystal plasticity, dislocation dynamics, molecular dynamics or other methods) and analytical (plasticity-based models, etc.) modelling of small-scale testing or deformation mechanisms.

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

Dr. Dhriti Bhattacharyya
Dr. Peter Hosemann
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • characterization
  • mechanical properties
  • mechanical testing
  • micromechanical testing
  • nanoindentation
  • nuclear materials
  • modelling
  • small-scale testing
  • larger-scale testing
  • deformation mechanisms
  • radiation damage

Published Papers (3 papers)

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Research

17 pages, 16325 KiB  
Article
Effect of He Plasma Exposure on Recrystallization Behaviour and Mechanical Properties of Exposed W Surfaces—An EBSD and Nanoindentation Study
by Dhriti Bhattacharyya, Matt Thompson, Calvin Hoang, Pramod Koshy and Cormac Corr
Metals 2023, 13(9), 1582; https://doi.org/10.3390/met13091582 - 11 Sep 2023
Cited by 1 | Viewed by 945
Abstract
Fusion reactors are designed to operate at extremely high temperatures, which causes the plasma-facing materials to be heated to 500 °C to 1000 °C. Tungsten is one of the target design materials for the plasma-facing diverter components in Tokamak designs, such as ITER, [...] Read more.
Fusion reactors are designed to operate at extremely high temperatures, which causes the plasma-facing materials to be heated to 500 °C to 1000 °C. Tungsten is one of the target design materials for the plasma-facing diverter components in Tokamak designs, such as ITER, because of its excellent high-temperature strength and creep properties. However, recrystallization due to high temperatures may be detrimental to these superior mechanical properties, while exposure to He plasma has been reported to influence the recrystallization behaviour. This influence is most likely due to the Zener effect caused by He bubbles formed near the surface, which retard the migration of grain boundaries, while at the same time modifying the surface microstructure. This paper reports a study of the effect of plasma exposure at different sample temperatures on the recrystallization behaviour of W at different annealing temperatures. The characterization after plasma exposure and annealing is pursued through a series of post-exposure annealing, followed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) characterization and nanoindentation to determine the mechanical properties. Here, it is shown that the hardness is closely related to the recrystallization fraction, and that the plasma exposure at a sample temperature of 300 °C slows down the recrystallization more than at higher sample temperatures of 500 °C and 800 °C. Atomic force microscopy (AFM) was subsequently used to determine any changes in pile-up height around the nanoindents, to probe any indication of changes in hardenability. However, these measurements failed to provide any clear evidence regarding this aspect of mechanical behaviour. Full article
(This article belongs to the Special Issue Advanced Characterization and Testing of Nuclear Materials)
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14 pages, 5584 KiB  
Article
Nanoindentation Investigation of Chloride-Induced Stress Corrosion Crack Propagation in an Austenitic Stainless Steel Weld
by Haozheng J. Qu and Janelle P. Wharry
Metals 2022, 12(8), 1243; https://doi.org/10.3390/met12081243 - 23 Jul 2022
Cited by 2 | Viewed by 1920
Abstract
Transgranular chloride-induced stress corrosion cracking (TGCISCC) is a mounting concern for the safety and longevity of arc welds on austenitic stainless steel (AuSS) nuclear waste storage canisters. Recent studies have shown the key role of crystallography in the susceptibility and propagation of TGCISCC [...] Read more.
Transgranular chloride-induced stress corrosion cracking (TGCISCC) is a mounting concern for the safety and longevity of arc welds on austenitic stainless steel (AuSS) nuclear waste storage canisters. Recent studies have shown the key role of crystallography in the susceptibility and propagation of TGCISCC in SS weldments. Given that crystallography underlies mechanical heterogeneities, the mechanical-crystallographic relationship during TGCISCC growth must be understood. In this study, welded SS 304L coupons are loaded in four-point bend fixtures and then boiled in magnesium chloride to initiate TGCISCC. Nanoindentation mapping is paired with scanning electron microscopy (SEM) electron backscatter diffraction (EBSD) to understand the correlation between grain orientation, grain boundaries, and hardening from TGCISCC propagation. The nanoindentation hardness of individual grains is found to not be a controlling factor for TGCISCC propagation. However, intragranular hardness is generally highest immediately around the crack due to localized strain hardening at the crack tip. This work shows that nanoindentation techniques can be useful in understanding CISCC behaviors when paired with electron microscopy. Full article
(This article belongs to the Special Issue Advanced Characterization and Testing of Nuclear Materials)
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8 pages, 1780 KiB  
Article
Hydrogen Degassing of Zirconium under High-Vacuum Conditions
by Francesco Fagnoni and Piotr Konarski
Metals 2022, 12(5), 868; https://doi.org/10.3390/met12050868 - 19 May 2022
Cited by 2 | Viewed by 1887
Abstract
Micromechanics techniques, such as nano-indentation and micro-pillar compression, can be applied to study hydrogen-charged zirconium alloys at elevated temperatures, which is highly relevant for the nuclear industry. Such experiments are often conducted inside a scanning electron microscope (SEM) under high-vacuum conditions (10−5 [...] Read more.
Micromechanics techniques, such as nano-indentation and micro-pillar compression, can be applied to study hydrogen-charged zirconium alloys at elevated temperatures, which is highly relevant for the nuclear industry. Such experiments are often conducted inside a scanning electron microscope (SEM) under high-vacuum conditions (10−5 mbar). The combination of a high-temperature and high-vacuum environment causes some hydrogen to escape from the sample into the chamber. Although this effect is evident at temperatures above 600 °C, the extent of hydrogen desorption at lower temperatures is still unclear. In the presented study, the desorption of hydrogen was assessed in zirconium cladding tube material under temperature and hydrogen content conditions comparable to those faced by used nuclear fuel during dry storage. The measured hydrogen loss due to the high vacuum was compared to the simulations obtained using an extended version of a hydrogen behavior tool developed at PSI. Full article
(This article belongs to the Special Issue Advanced Characterization and Testing of Nuclear Materials)
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