Radiation-induced Defects Research Articles

Defects analysis in low displacement damage neutron-irradiated austenitic stainless steels

Analysis of neutron irradiation-induced defects is carried out using Transmission Electron Microscope (TEM) on three variants of austenitic stainless steels, SS 304 L(N), SS 316 L(N), and SS 316 grid plate material irradiated in the Indian Fast Breeder Test Reactor at Kalpakkam to low displacement damage levels of 1.76–6.75 dpa at an irradiation temperature of 380 °C-400 °C and dpa rate in the order of 10−7dpa/s. There is a significant variation in the faulted dislocation loop size distribution and number density as a function of irradiation dose among these stainless steels due to their different stacking fault energies which is evident from the quantified defects data presented. At ∼5.08 dpa, SS 304 L(N), SS 316 L(N) and SS 316 exhibited faulted dislocation loop number densities of 2.3 × 1022/m3, 4.8 × 1021/m3, and 1.2 × 1022/m3 with mean loop sizes of 15.5 ± 6.3 nm, 35.4 ± 13.7 nm, and 16.1 ± 5.6 nm respectively. Thus, at an identical dpa level, SS 304 L(N) and SS 316 L(N) have the highest and the lowest faulted loop number densities respectively. The general size-distribution behaviour, the increment in the loop size with enhanced size distribution as a function of dpa is observed only for SS 316 L(N). The dislocation density data previously determined using X-ray diffraction analysis is correlated to the number density of dislocation loops along with their size distribution determined using TEM analysis. Finally, the change in the yield strength due to the increment in the faulted dislocation loop number density is determined.

Response of 11B enriched ZrB2 ultra-high temperature ceramic to neutron irradiation at elevated temperatures

ZrB2, an ultra-high temperature ceramic (UHTC) is being considered for use in fusion reactor first-wall structures, yet its response to irradiation remains poorly understood. This study employed scanning/transmission electron microscopy (S/TEM), synchrotron X-ray diffraction (XRD), finite element calculations, and thermal property measurements to thoroughly investigate the neutron-irradiation effects on 11B-enriched ZrB2. Neutron irradiations were conducted at 220 °C and 620 °C, with a neutron fluence of 2.2 × 1025 neutron/m2 (energy > 0.1 MeV), resulting in 3.9 dpa and 4200 appm He. The study revealed the unusual prevalence of prism loops and a > c anisotropic lattice swelling, likely linked to the low c/a ratio of ZrB2, leading to grain boundary microcracking. Reducing the grain sizes was effective in reducing intergranular cracking and macroscopic swelling. The observation of cavities in ZrB2 irradiated at 620 °C, as opposed to 220 °C, prompts questions about the temperature at which vacancies in ZrB2 become mobile, and the role of neutron absorption by 10B in elevating irradiation temperatures. Isotopic enrichment in 11B proves to be a viable strategy for mitigating helium production in transition-metal diborides, which is a critical consideration for nuclear applications. Irradiation-induced defects reduce the thermal diffusivity and conductivity of ZrB2 by a factor of 4–9, which has important implications for its role as a plasma-facing material in fusion reactors that drive high heat fluxes through first-wall materials. This comprehensive study lays the foundation for understanding ZrB2 behavior under neutron irradiation and highlights important phenomena to consider for various material applications.

In-situ TEM investigation of recovery mechanisms in ion-irradiated ITER-grade tungsten

The annealing of irradiation defects in tungsten was investigated under in-situ observations conducted using transmission electron microscopy (TEM). ITER-specification tungsten was exposed to heavy-ion irradiation by 10 MeV Au+ ions to 0.5 and 1 dpa at room temperature to generate defects. Subsequently, the thermal stability and recovery mechanisms of the generated defects are investigated by in-situ TEM at 600 °C, 800 °C, 900 °C and 1000 °C. The obtained TEM data are used to visualize and quantify the defect characteristics such as loops and voids as well as for observing the evolution of the microstructure and defect diffusion/recovery mechanisms. Focus is made on specific spatial phenomena such as loop-loop interaction, loop-dislocation and loop-grain boundary decoration, loop pinning, entanglement, formation of raft and transformation of loops into a dislocation network. The obtained results are in line with earlier obtained data for pure recrystallized tungsten, still, present results provide important information such as radiation-induced defect characteristics and recovery mechanisms under high temperature for the ITER-specification tungsten.

Role of defects in increasing the critical current density of reel-to-reel PLD (Eu,Er)Ba2Cu3Oy+BaHfO3-coated conductors

Given their excellent superconducting properties, REBa2Cu3Oy (REBCO)-coated conductors (CCs) are anticipated to be utilized in a variety of magnet applications. To further increase the critical current density J c of these materials to levels needed for commercial applications, this study employs reel-to-reel (RTR) pulsed laser deposition (PLD) to fabricate REBCO+BaHfO3 (BHO) CCs. PLD creates BHO nanorods, which serve as flux-pinning defects. The material is subjected to O2+ irradiation to introduce more defects. The irradiation-induced defects serve as flux-pinning centers to the REBCO+BHO-nanorod CCs, increasing J c along the c axis and over a wide range of magnetic-field angles compared with conventional REBCO+BHO-nanorod CCs. Both nanorods and irradiation-induced defects are demonstrated to be effective pinning centers in this material.

Extension of the scope of the photoluminescence method after electron irradiation for quantifying low-level carbon in silicon

We have extended the applicability of the photoluminescence method after electron irradiation for quantifying low-level C impurities in Si crystals. The intensity ratio of the G-line to the intrinsic emission normalized by the ratio of the reference sample is used as an index of the C concentration. The calibration curves have already been established for Czochralski-grown crystals with resistivity higher than 50 Ω·cm (n-type) and higher than 5 kΩ·cm (p-type). We showed that the method was extendable to the resistivity range down to 30 Ω·cm in n-type samples with the O concentration in the range 1–6 × 1017 cm−3. The extension to float-zone (FZ) crystals was realized by using the theoretical relationship between the C concentration and the G-line intensity ratio normalized by the ratio of the FZ reference sample. Regarding the extension to conductive p-type B-doped samples, the formation of B-related radiation-induced defects was found to be an obstacle.

Effect of Fe addition and ion irradiation on surface hardness in zirconium alloys: Experiments and modeling

Exploring the effect of Fe addition and ion irradiation on surface hardness in Zr alloys not only elucidates the strengthening mechanisms of individual alloying elements but also facilitates the assessment of mechanical properties under varying damage levels. In this work, the microstructural variations and surface hardness of Zr and Zr-Fe alloys were examined through Ne+ and Au3+ irradiation experiments. Electron backscatter diffraction (EBSD) characterization suggested the potential of Fe addition in Zr-Fe alloys for grain refinement. Transmission Electron Microscopy (TEM) observations indicated the formation of dislocation loops in irradiated materials, accompanied by a transformation of Zr3Fe particles from a crystalline to an amorphous state. Furthermore, nano-indentation tests were employed to measure the depth-dependent hardness, revealing an augmentation in hardness with increasing Fe content and highlighting noticeable irradiation hardening in Zr alloys. A mechanical model was then developed to theoretically investigate the contribution of diverse hardening mechanisms in ion-irradiated Zr alloys, particularly addressing the impact of non-uniformly distributed defects. Theoretical analysis denoted that the irradiation-induced defects hardening at varying depths follows distinct laws, whereas the precipitation hardening in Zr-Fe alloys was attributed to high-density strengthening particles induced by Fe addition. Moreover, it was determined that the surface hardness is governed by geometrically necessary dislocations (GNDs) and irradiation-induced defects at shallow depths, whereas precipitates and statistically stored dislocations (SSDs) dominate at relatively larger depths.

Analysis of the variation in mechanical properties of α- and β-SiC under high-temperature Si-ion irradiation

The mechanical properties of silicon carbide (SiC) under high-temperature irradiation have been one of the focal issues for its application in nuclear systems, but the relevant mechanisms remain elusive. In this work, two SiC polytypes inducing α- and β-phase were irradiated by 1.35 MeV Si5+ with a fluence of 1.81 × 1016 ions/cm2 at 550 °C and 750 °C, respectively, to investigate the characteristics of irradiation-induced defects and structure and the variation of mechanical properties. Irradiation significantly affected the mechanical properties of both α- and β-SiC. The nanohardness and modulus of α-SiC increased with the increase of irradiation temperature, while for β-SiC they first increased and then decreased significantly. The results of GIXRD and Raman spectra indicated the irradiation-induced defects, lattice deformation, and the changes in the intensity of the Si-C bond region. It was found that the TEM characterization of irradiated SiC samples with numerous point defect clusters, extended defects and a legible defect band. Moreover, the nanohardness and modulus of both SiC types exhibited a critical temperature dependence and were affected by different dominant factors at high temperatures. The potential mechanisms governing the variation in mechanical properties at elevated temperatures of two irradiated SiC polytypes were explored.

A mechanistic study of grain boundary behaviour during irradiation-induced growth in zirconium

Grain boundaries play a significant role during deformation and can exhibit both beneficial and adverse effects on deformation behaviour during irradiation. For instance, macroscopic irradiation growth is increased by the presence of a high density of grain boundaries. Grain boundaries can act as sinks for point defects and barriers to dislocation motion. Thus, a mechanistic assessment of the impact of grain boundaries is essential for better understanding irradiation-induced deformation. The interplay between irradiation-induced microstructure and mechanical properties has been an area of research for many decades, but many uncertainties remain. In the present work, the deformation fields adjacent to grain boundaries in pure zirconium are investigated by using high angular resolution electron backscatter diffraction (HR-EBSD) after a period of irradiation growth. It is observed that the extent of grain boundary deformation is associated with the crystallographic orientation difference between adjacent grains. High-angle grain boundaries function as a deformation constraint, whereas a significant grain boundary migration occurs at some low-angle grain boundaries, which likely act as an active diffusion path for the irradiation-induced point defects. In addition, the change in residual strain fields associated with the irradiation damage is quantified with respect to a non-irradiated reference. A net change in the state of residual elastic strain in the order of ∼10−3 has been estimated for ∼8 dpa proton irradiation. Furthermore, the origin of residual elastic strain and lattice misorientation concentration along (0002) traces are discussed.

Radiation-Induced Defects in Uranyl Trinitrate Solids.

Actinides are inherently radioactive; thus, ionizing radiation is emitted by these elements can have profound effects on its surrounding chemical environment through the formation of free radical species. While previous work has noted that the presence of free radicals in the system impacts the redox state of the actinides, there is little atomistic understanding of how these metal cations interact with free radicals. Herein, we explore the effects of radiation (UV and γ) on three U(VI) trinitrate complexes, M[UO2(NO3)3] (where M=K+, Rb+, Cs+), and their respective nitrate salts in the solid state via electron paramagnetic resonance (EPR) and Raman spectroscopy paired with Density Functional Theory (DFT) methods. We find that the alkali salts form nitrate radicals under UV and γ irradiation, but also note the presence of additional degradation products. M[UO2(NO3)3] solids also form nitrate radicals and additional DFT calculations indicate the species corresponds to a change from the bidentate bound nitrate anion into a monodentate NO3 • radical. Computational studies also highlight the need to include the second sphere coordination environment around the [UO2(NO3)3]0,1 species to gain agreement between the experimental and predicted EPR signatures.

Nanoindentation study on early-stage radiation damage in single-phase concentrated solid solution alloys

Concentrated solid solution alloys (CSAs) comprising multiple components have unlocked novel pathways for materials design, particularly in enhancing radiation tolerance. It is imperative to detect early-stage radiation damage in CSAs to gain insights into damage initiation and accumulation mechanisms. In this study, nanoindentation is employed to assess the impact of irradiation on deformation mechanisms in single crystal CSAs, specifically NiCo, NiFe, and NiCoFeCr. It is discovered that pile-up behavior in CSAs significantly affected by irradiation: pile-up induces 10–20 % increase in the contact area before irradiation that is independent of the penetration depth but 20–30 % after irradiation, which substantially affects hardness analyses. Within the context of strain gradient plasticity theory, distinct radiation-induced hardening in three CSAs is interpreted by two components: one is from the radiation-induced defects, and the other is the increase in density of geometrically necessary dislocations (GNDs) associated with indentation size effect (ISE). Quantitative analysis shows that the radiation-induced defects produce obvious hardening in NiFe and NiCoFeCr sample, but not in the NiCo sample. Meanwhile, the irradiation induces a higher GND density in NiCo and NiFe, but not in NiCoFeCr, which is interpreted by the volume change of the plastic zone.

Properties of radiation-induced point defects in austenitic steels: a molecular dynamics study

Austenitic steels are recognized as excellent structural materials for pressurized water reactors due to their outstanding mechanical properties and radiation resistance. However, compared to the widely studied FeCrNi series of steels, little is known about the radiation resistance of FeCrNiMn steel. In this study, the generation and evolution of radiation-induced defects in FeCrNiMn steel were investigated by molecular dynamics simulations. The results showed that more defect atoms were produced in the thermal spike stage, but fewer defects survived at the end of the cascades in FeCrNiMn compared to pure Fe. Point defect properties were analyzed by molecular statics, and the formation energies of defects in FeCrNiMn were lower than those of pure Fe, while the migration energies were higher. Compared to FeCrNi, FeCrNiMn had smaller migration energies and a larger overlap of vacancy and interstitial migration energies. The low vacancy formation energies and widely overlapping migration energies suggested that the number of point defects in the thermal spike stage was higher, but the possibility of recombination was greater. Additionally, Mn exhibited the smallest interstitial formation energies and migration energies. The difference in defect migration energies revealed that vacancy and interstitial defects migrate through different alloy constituent elements. This study revealed the underlying mechanism for the excellent irradiation resistance of FeCrNiMn.

Probing thermodynamics of radiogenic helium and defects in δ-plutonium alloys and interactions with adsorbed environmental gases

Differential scanning calorimetry coupled with simultaneous evolved gas analysis (DSC-EGA) on aged δ-Pu samples shows that most radiogenic helium remains trapped within the Pu matrix at temperatures very close to, or slightly above, the melting temperature. Our results indicate that helium release from 50-year-old δ-Pu occurs as a burst just below the melting temperature (>0.994 Tm), with subsequent pressure oscillations as temperature increases. Subordinate quantities of H2 were also released along with helium. The helium emission tails off and ceases above ∼720 – 750°C. In a δ-Pu alloy aged 6 years, the initial helium burst occurs slightly above melting (∼1.015 – 1.042 Tm), with a discrete, larger helium spike occurring between 670 and 686°C. The proximity of helium release to the liquidus transition presented challenges in the deconvolution of overlapping process enthalpies, the liquidus endotherm, and the exotherm resulting from bubble collapse, annealing and gas expulsion. Helium’s strong affinity for vacancy binding in a 2He-vac configuration is predicted by Density Functional Theory (DFT) modeling. The measured stored energy associated with the He release events in a 50-year-old δ alloy is on the order of ∼10–11 J/g, which is significantly higher than stored energies measured in the sub-solidus regimes (∼2 J/g) that are related to the solid-state annealing of processing- and radiation-induced defects. This implies that aged δ Pu alloys have a remarkable resilience to accommodate the lattice strain produced by the internal pressure of the helium bubbles and provides further insight into the thermodynamic behavior of aged δ Pu.

Compositionally complex carbide ceramics: A perspective on irradiation damage

Extensive experimental and computational studies have demonstrated outstanding physical and chemical properties of the novel materials of compositionally complex carbides (CCCs), enabling their promising applications in advanced fission and fusion energy systems. This perspective provides a comprehensive overview of radiation damage behavior reported in the literature to understand the fundamental mechanisms related to the impact of multi-principal metal components on phase stability, irradiation-induced defect clusters, irradiation hardening, and thermal conductivity of compositionally complex carbides. Several future research directions are recommended to critically evaluate the feasibility of designing and developing new ceramic materials for extreme environments using the transformative “multi-principal component” concept. Compared to the existing materials for nuclear applications including stainless steels, nickel alloys, ZrC, SiC, and potentially high-entropy alloys, as well as certain other compositionally complex ceramic families. CCCs appear to be more resistant to amorphization, growth of irradiation defect clusters, and void swelling.

Radiation-induced defects in the InGaN/GaN superlattice structure

With the molecular dynamics method, this paper investigates radiation-induced defects in the In0.16Ga0.84N/GaN superlattice structure (SLS) and the In0.04Ga0.96N/GaN SLS. In the temporal evolution of cascades, most of vacancies recombine with interstitials. The Monte Carlo simulations about the proportions of PKAs induced by 3 MeV protons were also considered in this work for calculating the weighted averages of surviving defects. For the In0.16Ga0.84N/GaN SLS irradiated by protons, around 82.6 percent of surviving vacancies are Ga vacancies while around 88.9 percent of surviving interstitials are Ga interstitials. For the In0.04Ga0.96N/GaN SLS irradiated by protons, around 87.3 percent of surviving vacancies are Ga vacancies while around 88.6 percent of surviving interstitials are Ga interstitials. N vacancies, N interstitials, and In vacancies also exist in irradiated InGaN/GaN SLS. Details about different types of defects are presented in this paper, which helps explain the microscopic mechanism of irradiated InGaN/GaN SLS. Since different types of defects have different influences on electronic and optical properties, simulations about the proportions of various defects in irradiated InGaN/GaN SLS help experimentalists find the effective factors of radiation-related changes in electronic and optical properties.

Effects of single and simultaneous Fe, He ions irradiations on CoCrFeMnNi high entropy alloy

Simultaneous irradiation was performed on CoCrFeMnNi high entropy alloy (HEA) at room temperature using Fe ions and He ions, and single Fe ions irradiation and single He ions irradiation were used as comparisons. The synergistic effect of the two ions on irradiation-induced defects such as dislocation loops and He bubbles, as well as the effect of irradiation damage on the nano-hardness were investigated. As the irradiation dose increased, a distribution with small and dense dislocation loops was first formed in CoCrFeMnNi HEA, and then these dislocation loops merged and grew. However, compared to pure metal, CoCrFeMnNi HEA entered the dislocation loop merging stage at a higher threshold dose due to its higher defect recombination capacity and higher critical stress of initial dislocation motion. Compared with the single Fe ions irradiation, the addition of He in the simultaneous irradiation accelerated the merging and growth of dislocation loops and decreased the density of dislocation loops. At the same He dose, simultaneous irradiation produced a higher vacancy concentration than single He ions irradiation, which increased He mobility, leading to wider He bubble layer and larger He bubble size. CoCrFeMnNi HEA hardened after irradiation with all three parameters in the order of single He ions irradiation > single Fe ions irradiation > simultaneous Fe+He ions irradiation. This study provided a deeper understanding of the irradiation damage mechanism of HEA in complex irradiation environment.

The radiation resistance and chemical stability optimization of analog actinide nuclides incorporated Gd2Zr2O7 ceramics via grain size control

Gd2Zr2O7 is considered a promising host material for immobilizing high-level radioactive waste. However, its interplay between grain sizes, radiation resistance and chemical stability is not well understood yet. Herein, Gd1.7Nd0.3Zr0.5Ce1.5O7 ceramics with defect-fluorite phase and three different grain sizes (96, 390 and 1959 nm) were successfully fabricated and irradiated by 140 keV He ion beam up to a fluence of 8 × 1017 ions/cm2. Phase evolutions, microstructure changes and chemical stabilities were investigated. The nano-grained ceramic exhibits the lowest degree of amorphization and a delayed irradiation-induced lattice expansion and damage evolution process, demonstrating an enhanced ability in suppressing the coalescence of He bubbles inside the grain. Grain boundaries parallel to the surface were found to be more favorable sinks for irradiation-induced defects. Chemical stability tests showed that the 42 days leaching rates of all elements were between 10−7∼10−5 g/m2·d. All samples have maintained this superior chemical stability even after irradiation. Interestingly, the leaching test results also suggested that grain size may be not the primary factor influencing the long-term leaching rate.

Interactions between irradiation-induced defects and dislocations in concentrated solid solution alloys

Dislocation is a common structural feature in metallic alloys. Under irradiation, interactions between dislocations and irradiation-induced defects play a crucial role in governing various microstructural changes and the irradiation response of materials. Though such interaction has been intensively studied in elemental metals, little is known about it in concentrated solid solution alloys (CSAs). In this work, we study defect-dislocation interactions in NiFe CSAs through both elastic theory and atomistic simulations. Unexpectedly, we find that dislocations interact more strongly with defects in CSAs than in pure metals due to their higher elastic moduli, which is adverse to their irradiation performance based on conventional understanding. By comparing random models (Rand) and average atom models (Ave) for NiFe, we show that the random occupancy of atoms in the Rand model compared to the Ave model can reduce the interaction between dislocations and defects, thereby diminishing the dislocation bias factor. We further perform defect kinetic simulations and find that the complex energy landscape for defect motion in NiFe tends to restrict the movement of defects and weaken the ability of dislocations to absorb interstitials. Therefore, the chemical disorder in CSAs can partly reduce the defect-dislocation interaction strength thermodynamically and, more importantly, limit the movement of defects kinetically, both of which suppress the absorption ability of dislocations toward defects. Our integrated efforts shed light on the mechanisms governing defect-dislocation interactions in CSAs, providing insight into the reasons for the superior irradiation resistance of CSAs and offering possible directions to tune their irradiation performance.

Comparative study on responses of three candidate materials for ADS beam/target windows to proton irradiation: T91, SIMP and Ti-6Al-4V

Accelerator-Driven System (ADS) represents an advanced nuclear energy system designed for the purpose of transmuting and eliminating nuclear waste. The irradiation tolerance of a material stands out as a critical factor in determining its availability for ADS beam/target windows. This study delves into the response of three promising candidates (T91, SIMP, and Ti-6Al-4V) for ADS beam/target windows to proton irradiation, as investigated by a 1.4 MeV H2+ irradiation experiment to dose of 1.5 peak dpa at 460 °C. Their cavity swelling and hardening behavior were estimated using Transmission Electron Microscope (TEM) and Nanoindentation, respectively. It was demonstrated that SIMP steel shows lower cavity swelling but slightly higher irradiation hardening compared to T91. Notably, no cavity swelling is observed in Ti-6Al-4V, but it experiences a higher level of irradiation hardening. The nucleation and evolution mechanisms of irradiation-induced defects (including cavities, dislocation loops, and precipitates) and their contributions to the proton irradiation response are discussed. Furthermore, a summary of the advantages and disadvantages of the three materials as candidates for proton beam/target windows is provided.

Mechanisms of ion irradiation induced ordering in amorphous TiO2 nanotubes: Effects of ion mass and energy

Amorphous TiO2 nanotubes were irradiated in-situ in a transmission electron microscope (TEM) with Kr+ ions at energies of 46 keV, 150 keV, and 1 MeV and with 46 keV Xe+ ions, to investigate the structural and morphological evolution of the nanotubes under irradiation. At all irradiation conditions, amorphous TiO2 nanotubes exhibited significant morphological instability, and tended to undergo volumetric swelling with increasing ion counts, often until collapse of the original nanotube structure. Molecular dynamics (MD) simulations confirmed that irradiation-induced defects can explain the observed swelling. Structurally, nanotubes remain amorphous following all Kr+ irradiation conditions, but irradiation with 46 keV Xe+ leads to the formation of anatase nanocrystallites. Importantly, through systematically varying ion energy and ion species, we try to elucidate the influence of nuclear and electronic stopping power on ion irradiation induced changes. By contextualizing these results within the existing literature, we propose that the observed changes in TiO2 nanotube morphology and structure could be due to a competition between two mechanisms: (1) disorder-induced swelling and (2) irradiation-induced amorphous-to-crystalline transformation.

Influence of electrical field on the susceptibility of gallium nitride transistors to proton irradiation

Radiation susceptibility of electronic devices is commonly studied as a function of radiation energetics and device physics. Often overlooked is the presence or magnitude of the electrical field, which we hypothesize to play an influential role in low energy radiation. Accordingly, we present a comprehensive study of low-energy proton irradiation on gallium nitride high electron mobility transistors (HEMTs), turning the transistor ON or OFF during irradiation. Commercially available GaN HEMTs were exposed to 300 keV proton irradiation at fluences varying from 3.76 × 1012 to 3.76 × 1014 cm2, and the electrical performance was evaluated in terms of forward saturation current, transconductance, and threshold voltage. The results demonstrate that the presence of an electrical field makes it more susceptible to proton irradiation. The decrease of 12.4% in forward saturation and 19% in transconductance at the lowest fluence in ON mode suggests that both carrier density and mobility are reduced after irradiation. Additionally, a positive shift in threshold voltage (0.32 V and 0.09 V in ON and OFF mode, respectively) indicates the generation of acceptor-like traps due to proton bombardment. high-resolution transmission electron microscopy and energy dispersive x-ray spectroscopy analysis reveal significant defects introduction and atom intermixing near AlGaN/GaN interfaces and within the GaN layer after the highest irradiation dose employed in this study. According to in-situ Raman spectroscopy, defects caused by irradiation can lead to a rise in self-heating and a considerable increase in (∼750 times) thermoelastic stress in the GaN layer during device operation. The findings indicate device engineering or electrical biasing protocol must be employed to compensate for radiation-induced defects formed during proton irradiation to improve device durability and reliability.