Radiation Damage Accumulation Research Articles

STUDY OF STRUCTURAL DAMAGE MECHANISMS IN STABILIZED CERAMICS BASED ON ZIRCONATES UNDER HIGH-TEMPERATURE IRRADIATION WITH HEAVY IONS

The paper presents a comprehensive description of the results of experimental work related to the study of the mechanisms of radiation damage accumulation during the irradiation with heavy Xe+ ions of the studied samples of Nd2Zr2O7 ceramics in the unstabilized state, and stabilized with 0.15 M MgO and Y2O3, the adding of which according to the data of X-ray phase analysis leads to the formation of impurity inclusions in the structure in the form of MgO and Y2Zr2O7 grains, which create a buffer protective layer in the intergranular space, the presence of which leads to an increase in resistance to radiation-induced processes of unstrengthening and reduction of thermophysical parameters. In the course of determining the dependences of changes in strain distortion resulting from the accumulation of structural stresses in the crystal structure and amorphization, which was determined on the basis of changes in the intensity of diffraction maxima, the equally probable influence of both processes at high-dose irradiation on the degradation of the near-surface damaged layer was determined, as well as the positive influence of stabilizing components on the inhibition of amorphization and strain distortion at high-dose irradiation. The analysis of changes in strength and thermophysical parameters of Nd2Zr2O7 ceramics subjected to irradiation by heavy ions has shown that the addition of stabilizing additives in the form of MgO and Y2O3 to ceramics composition leads to increased resistance to radiation-induced processes of de-strengthening and thermal conductivity degradation caused by the accumulation of structural deformation distortions and metastable inclusions in the damaged layer.

Effects of high temperature annealing and low temperature metamictization on Archean zircon: constraints from U–Pb isotopes, trace elements and Raman dating

Abstract Zircon is a common accessory mineral that can survive extreme temperature conditions in the crust, although U-Th series radioactive decay is responsible for its self-destruction over long time scales. Upon exhumation at lower temperatures, metamict zircon grains are then more susceptible to isotopic and trace element disturbance. In this work, we investigated the isotopic and trace element behavior of zircon through LA-ICP-MS, coupled with Raman spectroscopy, from two Archean mylonitic samples within the São José do Campestre Massif, northeastern Brazil. U–Pb in zircon dating indicates Paleoarchean (3.3 Ga) sedimentation followed by Mesoarchean (3.0–2.9 Ga) high temperature metamorphism in the mylonitic paragneiss sample, while the mylonitic amphibolite was emplaced during the late Neoarchean (2521 ± 22 Ma) and reached high-temperature conditions during shear zone development and deformation during the Paleoproterozoic (2.0 Ga). Inherited zircon grains in the amphibolite are consistent in morphology and ages with zircon grains from the host paragneiss. However, high temperature annealing and structure recovery upon entrainment of inherited zircon grains in the hot mafic magma led to homogenization of trace elements and preservation of internal textures. On the other hand, zircon grains from the host paragneiss accumulated radiation damage for a longer time, leading to self-destruction of the crystalline structure. Upon later low temperature fluid influx, non-formula elements were incorporated in metamict grains, as evidenced by the positive correlation between trace elements and radiation damage. Raman zircon dating indicates Cambrian to Late Paleozoic exhumation for these rocks, which agrees with U–Pb in zircon lower intercept ages. Although often avoided in geochronological studies, metamict zircon can provide important constraints on low temperature events. Collectively, these observations show a complex trans-crustal history of zircon recycling and exhumation from the Paleoarchean to the Paleozoic and the rock-dependent behavior of zircon upon fluid flow and deformation. The results have implications for the interpretation of trace 36 elements in naturally annealed zircon grains, especially those inherited in mafic rocks.

Atomistic simulation of chemical short-range order on the irradiation resistance of HfNbTaTiZr high entropy alloy

High entropy alloys (HEAs) have been considered as one of the potential structural material candidates for fourth-generation nuclear reactors and fusion reactors due to their excellent irradiation resistance. Current studies have shown that the chemical short-range order (CSRO) usually exists in HEAs, which has a significant effect on the mechanical properties and irradiation resistance of HEAs. Refractory high entropy alloys (RHEAs), as a new class of HEAs have better mechanical properties at high temperatures than face-centered cubic (FCC) HEAs, and therefore have better prospects of application in the nuclear field. In this study, CSRO and its effect on the irradiation resistance of HfNbTaTiZr are analyzed via molecular dynamics (MD) and Monte Carlo (MC). The primary cascade simulations, multi-cascade simulations and surface bombardment simulations are carried out to simulate the generation and accumulation of irradiation damage. The results of the primary cascade simulations and surface bombardment simulations of CSRO models show that the presence of CSRO induces cascade splitting into subcascades. The presence of subcascades reduces the thermal peak enhancement effect and thus lowers the recombination rate of Frenkel pairs (FPs) in the damage zone when FPs concentrations are low. However, the creation of subcascades increases the size of the damage zone caused by the cascade. Thus, when the concentrations of FPs are high, the larger area of damage zone allows more of the already existing FPs to be included, thus promoting their recombination, i.e., impedes their accumulation when concentrations are high. These subcascades lower the recombination of FPs at low FPs concentrations but inhibit their accumulation at high FPs concentrations. The presence of CSRO is also beneficial in inhibiting the growth of point defect clusters, which further improves the resistance of HfNbTaTiZr to dislocation generation. Furthermore, the presence of CSRO facilitates the irradiation-induced phase transition. But it is found that HfNbTaTiZr shows suppression of hexagonal close-packed (HCP) cluster growth. And the tendency to break down large HCP clusters into smaller ones is demonstrated in the CSRO model. From our calculations we also find that the irradiation-induced HCP atoms have a higher potential energy relative to the matrix. The potential energy difference between those energetic HCP atoms and the matrix can lead to generating a great number of insurmountable barriers pervading the matrix and largely suppressing the long-term mobility of FPs, thus limiting their aggregation and growth into clusters.

The connection between the accumulation of structural defects caused by proton irradiation and the destruction of the near-surface layer of Li4SiO4 – Li2TiO3 ceramics

The key problem of using lithium-containing ceramics as materials of breeders for the propagation of tritium in thermonuclear reactors is phase stability, as well as the preservation of strength and thermophysical parameters of ceramics during their operation, which is accompanied by the accumulation of fission products in the near-surface layers, alongside mechanical influences from the outside. Moreover, in contrast to other types of ceramics, the presence of lithium in the composition of the samples under study leads to limitations in the use of classical analysis methods (scanning electron microscopy, energy dispersive analysis or optical spectroscopy) of structural changes caused by the accumulation of radiation damage, which requires the use of more complex methods for the assessment of the defect concentration in the structure, as well as establishing their relationship with the deterioration of strength and thermophysical parameters, playing a key role in determining the stability mechanisms and further exploitation of ceramics for tritium production. In this regard, the aim of the study is to determine the kinetics of changes in the near-surface layer of two-phase Li4SiO4 – Li2TiO3 ceramics associated with the accumulation of structural distortions caused by irradiation, as well as their relationship with strain embrittlement and disorder. During the studies, it was found that the accumulation of implanted hydrogen in the near-surface layer under high-dose irradiation initiates deformation distortion processes, the intensity of which depends on the ratio of components in the ceramics, according to which the optimal compositions of two-phase ceramics are ratios of components from 0.3 to 0.6. Determination of the type of defects in the composition of the damaged layer, as well as their concentration, was carried out using the electron spin resonance (ESP) method. During the studies, it was found that at low irradiation fluences, the dominant role in the accumulation of structural defects is played by vacancy defects associated with E′-centers, the formation of which is associated with structural distortions, while as the fluence grows, the structure is dominated by deformation disordering caused by the accumulation of Ti3+ defects and HC2 centers (SiO43-), the concentrations of which have a clear dependence on the phase composition of the ceramics.

Thermally activated damage recovery in ion‐irradiated Gd2Ti2‐yZryO7 pyrochlore

AbstractIonizing events having a wide variety of radiation‐induced effects can radically affect the kinetics of defect production or structural transformation in the pyrochlore structured oxides (A2B2O7). Therefore, a thorough understanding of the kinetics associated with cation ordering and disordering is required for various technological applications. The structural responses of Gd2Ti2‐yZryO7 (y = 0.4, 1.2, 1.6) pyrochlore series irradiated by 120 MeV Au9+ ions were investigated using in situ synchrotron x‐ray diffraction (SR‐XRD), micro‐Raman spectroscopy, and scanning electron microscopy (SEM). Each pyrochlore composition irradiated at the highest fluence, where structural modifications occur, was subsequently isochronally annealed from room temperature to 1000°C. The SR‐XRD results indicate that Ti‐rich composition (y = 0.4) retains its pre‐irradiated pyrochlore structure (Fdm) at 1000°C. In contrast, Zr‐rich compositions exhibit recrystallization to an intermediate defect‐fluorite phase (Fmm) above 500°C, and the pre‐irradiated pyrochlore superstructure does not recover even on annealing at 1000°C. These results reveal that recrystallization temperature strongly depends on the accumulated radiation damage, generally described with the cationic radius ratio (rA/rB). Thus, investigation of the thermal annealing behavior of irradiated pyrochlores helps better understanding the general mechanisms of radiation damage and recovery of pyrochlores, which is important for their use in nuclear applications.

Simulations of radiation damage accumulation in Fe-9Cr under pulsed irradiation conditions representative of inertial fusion energy

Structural materials for laser-based inertial fusion energy (IFE) reactor concepts are expected to operate under pulsed irradiation conditions, with cycles consisting of microsecond-long neutron bursts followed by inter-pulse periods of up to one second in duration. During each laser shot, irradiation damage is introduced at dose rates that are up to six orders of magnitude higher than those in their magnetic fusion energy (MFE) counterparts. Under certain conditions, the inter-pulse periods may last an amount of time sufficient to anneal much of the damage introduced during each shot. This phenomenon is highly temperature dependent, with pulsed heating directly linked to the pulsed damage, large surface temperature spikes may also occur. As such, this intermittent mode of operation has the potential to lead to fundamental differences in how irradiation damage accumulates in structural reactor materials. However, damage to structural materials under IFE conditions has received comparatively much less attention than in MFE, as pulsed conditions add yet an extra dimension to the already extremely challenging problem of microstructural evolution under fusion neutron irradiation in structural materials. In this work we use the stochastic cluster dynamics (SCD) method to simulate the evolution with time of defect cluster concentrations under IFE conditions. We consider the Laser Inertial Fusion Energy (LIFE) reactor concept as the representative IFE design for our study, for which detailed spectral information is available, including gas transmutant production. We simulate several pulse frequencies and three different temperatures, and compare the results with continuous irradiation cases under identical average dose rates. The simulations are run in Fe-9Cr system as a model alloy for reduced-activation ferritic/martensitic (RAFM) steels, which are the leading structural material candidates for first-wall structures in MFE and IFE devices. We find that, in practically all scenarios, pulsed irradiation restricts the formation of helium-vacancy clusters relative to the levels seen under equivalent steady irradiation conditions. As well, although self-interstitial atom clusters do accumulate under pulsed operation, their number densities remain up to an order of magnitude lower than in continuous irradiation conditions. Based on the SCD results, we provide a temperature-pulse rate map to identify regions where pulsed irradiation may lead to larger defect accumulation than under continuous irradiation.

Unusual nanoscale amorphization of metallic chromium interfacing with SiC under high energy irradiation

Layered metal/silicon carbide (SiC) materials systems are becoming increasingly relevant to solve materials challenges in advanced fission and fusion nuclear energy systems, necessitating a deeper understanding of how interfaces between dissimilar materials behave under high energy irradiation. In this work, we use a Cr-SiC bilayer system as a model to study the behavior of such interfaces under high energy ion irradiation (80 MeV Xe26+ ions) at elevated temperatures (∼350 °C). Through high resolution characterization of the interface, we observed the formation of a nanoscale Cr-rich amorphous layer adjacent to crystalline SiC. We explain this phenomenon through a multi-scale computational approach incorporating ballistic mixing simulations, density functional theory calculations, and CALPHAD-based non-equilibrium modeling that shows the localized amorphization of Cr to be driven by the synergistic action of irradiation-induced point defects within Cr and transport of Si and C atoms across the interface. In particular, the accumulation of radiation damage results in the thermodynamic destabilization of the point-defect containing, metastable Cr-Si-C solid solution with respect to an amorphous phase of identical composition. This study advances the understanding of how metal/SiC interfaces behave under irradiation and establishes a modeling framework that can be applied to interfacial systems to understand irradiation-induced amorphization.

Determination of gamma radiation shielding efficiency by radiation-resistant composite ZrO2–Al2O3 – TiO2–WO3 – Nb2O5 ceramics

This work examines the prospects of using composite ZrO2–Al2O3 – TiO2–WO3 – Nb2O5 ceramics as shielding and radiation-resistant materials as structural materials in conditions of heightened radiation background, including gamma radiation and exposure to heavy ions. The key objective of the study is to determine the impact of the variation in composite ceramic composition on resistance to radiation damage caused by exposure to heavy ions comparable to nuclear fuel fission fragments, and to establish the effect of the radiation damage accumulation on the shielding characteristics of these ceramics, the maintenance of which determines the stability of the operation of nuclear materials by eliminating the ionization factor caused by the interaction of gamma quanta. During the studies, it was found that alterations in the phase composition of composite ceramics associated with the formation of ZrTiO4, AlWO3 and Nb2W3O14 phases in the structure lead not only to strengthening of the ceramics, but also to a rise in resistance to radiation damage, and associated changes in the damaged layer degradation, having an adverse impact on the shielding characteristics.

Revealing the critical role of vanadium in radiation damage of tungsten-based alloys

Refractory tungsten-based medium- and high-entropy alloys form a promising class of strong, heat- and radiation-resistant materials for nuclear applications. Here, we systematically explore the radiation tolerance of Mo–Nb–Ta–V–W alloys using molecular dynamics simulations and a machine-learned interatomic potential. Going from pure W to W-based equiatomic binaries, ternaries, quaternary, and the quinary high-entropy alloy, we simulate the radiation damage accumulation up to 0.4–0.8 dpa through cumulative collision cascades. We find that the radiation damage and evolution are controlled by a combination of cascade-induced clustering, the balance in migration of vacancies and interstitials, and defect cluster binding energies. These mechanisms are strongly influenced by atom size, among which vanadium as the smallest atom is decisive. In pure W and alloys without V, the microstructure is characterised by large and growing interstitial dislocation loops. In stark contrast, in alloys containing V, vacancy dislocation loops are formed directly in collision cascades and the balanced migration rate of vacancies and interstitials promotes recombination and prevents growth of interstitial loops. The atom size differences also lead to clear segregation, with small atoms (V) in interstitial clusters and larger atoms (Ta, Nb) segregating around vacancy clusters. Furthermore, the small cluster sizes, formation of vacancy loops, segregation, and balanced migration in V-containing alloys lead to low swelling and an exceptionally efficient defect annealing compared to pure W and V-free alloys. Our results highlight WTaV as a promising low-activation material, where almost 90% of defects are annealed at 2000 K during 5 ns compared to <20% in pure W.

Study of the Surface-Layer Softening Effects in xLi2ZrO3–(1−x)Li4SiO4 Ceramics under Irradiation with He2+ Ions

The study investigates alterations in the mechanical and thermophysical properties of ceramics composed of xLi2ZrO3–(1−x)Li4SiO4 as radiation damage accumulates, mainly linked to helium agglomeration in the surface layer. This research is motivated by the potential to develop lithium-containing ceramics characterized by exceptional strength properties and a resistance to the accumulation of radiation damage and ensuing deformation distortions in the near-surface layer. The study of the radiation damage accumulation processes in the near-surface layer was conducted through intense irradiation of ceramics using He2+ ions at a temperature of 700 °C, simulating conditions closely resembling operation conditions. Following this, a correlation between the accumulation of structural modifications (value of atomic displacements) and variations in strength and thermophysical characteristics was established. During the research, it was observed that two-component ceramics exhibit significantly greater resistance to external influences and damage accumulation related to radiation exposure compared to their single-component counterparts. Furthermore, the composition that provides the highest resistance to softening in two-component ceramics is an equal ratio of the components of 0.5Li2ZrO3–0.5Li4SiO4 ceramics.

Connecting visual metamictization to radiation damage to expand applications of zircon (U-Th)/He thermochronometry

Zircon (U-Th)/He (ZHe) thermochronometry quantifies the timing and tempo of low-temperature processes and is used to deconvolve tectonic and erosional histories. Accumulation and annealing of radiation damage impacts He diffusion in zircon and resulting ZHe dates. Resolving complex histories requires building relationships between ZHe date, effective U (eU), and radiation damage in grains sharing a common thermal history. Prior work demonstrated that purposefully selecting grains with a spectrum of visual metamictization yields a broad range of intrasample eU values (Ault et al., 2018), but it remained unclear if visual metamictization tracks effective radiation damage. Here we evaluate relationships between visual metamictization, effective damage calculated from Raman spectroscopy, and ZHe dates from a new suite of grains from some of the same Precambrian samples investigated in Ault et al. (2018) and Phanerozoic detrital grains from Armstrong et al. (2022). New ZHe analyses (n = 21) confirm increasing visual metamictization corresponds with increasing eU concentration and dates fall along previously reported ZHe date-eU trends for each sample, despite grain selection by different analysts in different sessions. Raman-based alpha dose calculations from multiple spot analyses from transects across the surface and interior of each grain (n = 480 total analyses) range from 3.19 × 1016 to 1.52 × 1019 α/g across the whole dataset. Alpha dose increases in samples characterized by a clear increase in visual metamictization from different types of ZHe date-eU patterns, supporting that visual metamictization reflects effective radiation damage in these samples. Complexities in visual metamictization-damage trends are due to damage zonation observed in cathodoluminescence, comparative internal and external spot analyses, and 2-D Raman maps, as well as limited spread in intrasample visual metamictization and user grain selection bias. Overall, visual metamictization provides a qualitative estimate of effective damage and should be leveraged when selecting grains for traditional ZHe analyses to build ZHe date-eU-damage patterns.

Effects of radiation damage on the yielding and fracture of nanowires.

Since free surfaces act as perfect sinks for radiation-induced defects, nanowires, owing to their high surface-to-volume ratio, are considered to be radiation tolerant. But the question remains on how this tolerance translates to their yielding and fracture behavior. Atomistic simulations of irradiated gold nanowires reported here show the existence of a size regime where the yield stress is affected by the accumulation of radiation damage. Our analysis also shows that, regardless of the diameter of the nanowire, early on during tensile loading, much of the radiation-induced defect content initially present in the wire is rapidly cleaned by the motion of pre-existing dislocations as well as dislocations emitted from the surface of the wire. This defect removal process resets the crystallographic configuration of the wire which subsequently deforms and fractures via the same mechanisms that occur in pristine, un-irradiated nanowires. We conclude that the fracture behavior of nanowires in the size and dose regimes tested is unaffected by radiation damage.

Calculation of radiation damage of key components of China Spallation Neutron Source II target station

China Spallation Neutron Source (CSNS) I project passed the national acceptance in 2018, and current beam power has reached 140 kW. In order to further improve the output neutron strength of the target station moderator, a 500 kW power upgrade plan has been proposed for CSNS II. The target station is an important part of the spallation neutron source. In the target station, a large number of neutrons are produced by the spallation reaction between high energy protons and the target, these neutrons are moderated by the moderator and become neutrons for neutron scattering experiments. During operation, the target and other key components such as the target container, the moderator reflector container, and the proton beam window are irradiated by high-flux and high-energy particles for a long time, which will result in serious radiation damage. It is important to assess the accumulated radiation damage during operation to determine the service life of each component. At present, the physical quantities used to evaluate the radiation damage degree of materials include displacement per atom (DPA), H and He production. In this work, the displacement damage cross sections of protons and neutrons and the H, He production cross sections for W, SS316 and Al-6061 materials are obtained by using PHITS. The effects of the Norgett-Robinson-Torrens (NRT) model and athermal recombination corrected (ARC) model on the calculation of displacement damage are analyzed. The results show that the cross section calculated based on ARC model is lower than that based on NRT model, because the NRT model does not take into account the resetting of the atoms before reaching thermodynamic equilibrium. On this basis, DPA, H and He production of the key components of the target station operating for 5000 h at a power of 500 kW are calculated by combining the baseline model of the second phase target station of the spallation neutron source in China. The results show that the yields of NRT-dpa, ARC-dpa, H and He produced by irradiation are 8.01 dpa/y (in this paper, 1 y = 2500 MW·h), 2.39 dpa/y, 5110 appm/y and 884 appm/y, respectively. The radiation damage values of the target vessel are 5.34 dpa/y, 1.92 dpa/y, 2180 appm/y and 334 appm/y, respectively. The radiation damage values of the moderators and reflectors are 3.78 dpa/y, 1.77 dpa/y, 124 appm/y, and 36.7 appm/y. The radiation damage values of the proton beam window are 0.35 dpa/y, 0.19 dpa/y, 962 appm/y, and 216 appm/y. Subsequently, the life of each component is estimated by analyzing the radiation damage. These results are very important for analyzing the radiation damage of these parts, and constructing reasonable maintenance programs.

Radiation Damage Accumulation in α-Ga2O3 under P and PF4 Ion Bombardment

Radiation Damage Accumulation in α-Ga2O3 under P and PF4 Ion Bombardment

A refined numerical simulation approach to assess the neutron irradiation effect on the mechanical behavior of wurtzite GaN

Neutron irradiation often produces distinct types of damage or defects in gallium nitride (GaN) materials, which could alter the mechanical properties of GaN. This work develops a numerical approach utilizing molecular dynamics (MD) simulation to capture the structural changes and defect evolution characteristics of wurtzite GaN under long-term low-dose neutron irradiation, and to evaluate the variations in fundamental mechanical properties. By comparing different types of potential functions available for describing GaN materials, the Tersoff/ZBL potential energy function is found to be more suitable for describing the irradiation effects of GaN. A method of using multiple recoil atoms to trigger cascade collision together with a three-stage irradiation process description is proposed to achieve an effective distribution of irradiation defects, as well as to improve computational efficiency. To simulate the irradiation damage accumulation due to successive cascade collisions, it is applicable to apply an iterative process for the simulation model. Using these approaches, uniaxial tension simulations for irradiated wurtzite GaN are performed to analyze the variations in its fundamental mechanical properties along [1 0 1¯ 0] crystalline direction. The results indicate that low-dose irradiation tends to decrease the Young's modulus and tensile strength of wurtzite GaN material, and could alter its deformation mechanisms to some extent.

MD simulation of primary radiation damage in fcc multi-principal element alloys: Effect of compositional undulation

Fcc single phase alloys with highly concentrated solid solution are competitive candidates for the next-generate radiation-tolerant materials. The present study uses molecular dynamics simulations to study the displacement cascades of NiCoFeCr fcc single-phase concentrated solid-solution alloys (SP-CSAs). The effects of compositional undulation on the generation and evolution of the defects, produced by primary knock-on atoms, are quantitatively analysed. Our simulation results show that the undulation renders considerable compositionally graded interfaces (CGIs) with high threshold energy for displacement, and these CGIs can act as pre-existing defect sinks and confine interstitial defects motion. This increases the recombination rate of residual defects, thus leading to the suppression of Frenkel pairs and large-sized interstitial clusters. In addition, such effect of compositional undulation is correlated with the specific chemical elements, i.e., the Ni-Fe and Co-Fe undulated SP-CSA yield slower radiation damage accumulation. Our findings suggest a new degree of freedom to tailor radiation-tolerance for concentrated solid-solution alloys.

Hydrothermal alteration, not metamictization, is the main trigger for modifying zircon in highly evolved granites

The question of whether the high U and Th concentrations in zircon are primary or secondary is often difficult to resolve, and a clear understanding of the modification processes of secondary U- and Th-rich zircon is lacking. Zircon crystals from two well-studied, highly evolved granites, the Jiangjunshan muscovite granite in the Chinese Altai Mountains and the Cuonadong leucogranite in the Eastern Tethyan Himalaya, have been investigated and classified into two types. Type I exhibits typical igneous growth zoning, and type II has “diffuse” or “spongy” internal structures. These textures, along with compositional data, indicate that the type II zircon crystals formed through hydrothermal modification of magmatic zircon (type I) by infiltrating hydrothermal fluids. During hydrothermal modification, the U and Th concentrations increase from type I to type II in the Jiangjunshan muscovite granite but decrease from type I to type II in the Cuonadong leucogranite. The Raman spectra of type II zircon crystals from Jiangjunshan muscovite granite have broader peaks (i.e., measured as the full width at half maximum, FWHM) with decreased intensities than their type I counterparts, which indicates that the former are affected by significant accumulated radiation damage. However, the preserved radiation damage in both the type I and II zircon measured by Raman spectroscopy is less than that expected from the total dose of alpha particles calculated from the U and Th contents, which indicates variable degrees of annealing. We propose that late magmatic-hydrothermal alteration was responsible for the modification of magmatic zircon grains in highly evolved granites and resulted in the enrichment or redistribution of U and Th. The calculated radiation dose of the Cuonadong leucogranite zircon is far below that required for metamictization, which indicates that metamictization is not always responsible for diffuse and spongy textures.

Study of the Kinetics of Radiation Damage in CeO2 Ceramics upon Irradiation with Heavy Ions

In this work, the effect of irradiation with heavy Kr15+ and Xe22+ ions on the change in the structural and strength properties of CeO2 microstructural ceramics, which is one of the candidates for inert matrix materials for dispersed nuclear fuel, is considered. Irradiation with heavy Kr15+ and Xe22+ ions was chosen to determine the possibility of simulation of radiation damage comparable to the action of fission fragments, as well as neutron radiation, considering damage accumulation at a given depth of the near-surface layer. During the research, it was found that the main changes in the structural properties with an increase in the irradiation fluence are associated with the crystal lattice deformation distortions and the consequent radiation damage accumulation in the surface layer, and its swelling. Evaluation of the effect of gaseous swelling caused by the radiation damage accumulation showed that a variation in the ion type during irradiation results in a growth in the value of swelling and destruction of the near-surface layer with the accumulation of deformation distortions. Results of the strength variation demonstrated that the most intense decrease in the near-surface layer hardness is observed when the fluence reaches more than 1013–1014 ion/cm2, which is typical for the effect of overlapping radiation damage in the material.

Molecular dynamics study of the irradiation damage accumulation in beryllium oxide at different temperatures

Beryllium oxide as a nuclear material has received renewed attention in recent years, and it is critical to investigate the irradiation behavior. The irradiation damage accumulation in beryllium oxide is investigated by molecular dynamics method. The evolution of defects and the degree of amorphization have been revealed as a function of dose at different irradiation temperatures. The dislocation induced by irradiation is obvious only when the irradiation temperature is above 873 K. A new cubic diamond structure appears at higher irradiation temperatures. Simulated XRD results are closely related to the degree of amorphization. In addition, the influence of irradiation damage on the compressive strength of beryllium oxide under different irradiation conditions is also studied.

Helium bubble formation in additive manufactured L-PBF AlSi10Mg

Laser powder bed fusion additive manufacturing shows great promise for the nuclear industry due to unique and novel metallurgical phenomena and superior properties compared to cast or wrought products. The correlation between the unique microstructure of additively manufactured AlSi10Mg alloy, the radiation damage accumulation and its effect on the mechanical properties is examined. Laser powder bed fusion AlSi10Mg alloy was subjected to He+ ions implantation over an energy range that produced a 2 μm uniform layer within the bulk material to yield a local dose of 2000 appm at the depth of the material. It is shown that for each microstructural component the Helium bubble size, distribution and density depends on its stopping range. Furthermore, the overall increase in nanohardness in the irradiated region is in correlation with the measured defect density. In this unique microstructure interfaces play a diminished role at accumulating Helium bubbles compared to dislocations and dislocation structures indicating their relative sink strength.