Since September 11, 2001, the Centers for Disease Control and Prevention (CDC) has increased efforts to prepare the agency and public health partners for response to potential nuclear/radiological disasters. During the week of May 16–20, 2022, the CDC participated in a national-level radiological emergency exercise, Cobalt Magnet 22 (CM22). The exercise scenario consisted of a notional, failed search mission for a radiological dispersal device (RDD, “dirty bomb”), followed by its explosion during a public event in a large US city. Testing radioanalytical laboratory capabilities during a nuclear/radiological incident was an exercise objective, and developing clear messaging on low-dose exposure and long-term health concerns was a primary output of the exercise. The CDC practiced its activation protocols, exercised the establishment of its updated Incident Management System structure for radiation emergencies, and identified critical staffing needs for this type of response.

Localized deformation, including that by the deformation-induced shearing martensitic phase transformation, is responsible for hardening and embrittlement in irradiated face-centered cubic alloys. These localized deformation processes can have profound consequences on the mechanical integrity of common structural metals used in extreme radiation environments such as nuclear reactors. This article aims to review and understand exactly how irradiation affects the martensitic phase transformation in face-centered cubic alloys, with an emphasis on austenitic stainless steel, given its ubiquity in the archival literature. The influence of irradiation on stacking fault energy and subsequent implications on the phase transformation are discussed. Mechanisms by which irradiation-induced microstructures enhance the phase transformation are also described, including the surface energy contribution of irradiation-induced cavities (i.e., voids and bubbles) toward the critical martensite nucleation energy, and partial dislocation–cavity interactions. A deformation mechanism map illustrates how irradiation-induced cavities can modulate the martensitic transformation pathway.

In a deep geological repository (DGR) scenario, uranium oxidized in aqueous systems will be stabilized as UO22+ (hexavalent uranium), as a consequence of tetravalent uranium oxidation by radiolytic byproducts. Uranyl cationic species (UO22+) in different speciation forms are expected to be found at the whole pH range conditions. The importance of UO22+ lies in its potential incorporation of trace radioelements onto secondary uranyl phases. In view of the difficulty of U chemistry in natural groundwater, it is necessary to improve speciation assessment techniques so as to understand chemical processes. Raman spectroscopy has been shown as a powerful tool to analyze the speciation of various actinyl (UO22+,NpO2+ and PuO22+) and to determine the distribution of those elements which are more likely to be stable in a near-field groundwater environment. Therefore, the aim of this work is to follow UO22+ changes as a consequence of γ radiation in aqueous media under DGR conditions, and to understand the behavior of UO22+ as a function of aqueous media, which help to understand and predict the potential precipitation of the solid phases formed. In this work, the use of Raman spectroscopy adapted to the empirical analysis of different nuclear applications for initial uranium concentrations 0.04M at ambient atmosphere is shown, i.e. as monitoring tool for UO22+ precipitation as a function of pH, studying UO2(NO3)2·6H2O stability in aqueous solutions representative of groundwater, in particular at ionic strength I = 0.02 – 0.4 M and pH from 7 to 13.2; and to evaluate the effect of γ radiation fields. At 10−4-10-3 M of radiolytically formed H2O2 concentration, the amount of uranium in solution decreased, as a results of secondary phases precipitation. The results obtained will be useful to the performance assessment studies of the Spent Nuclear Fuel (SNF) stored in DGRs. The work performed provides a partial picture of secondary phase formations, as a result of corrosion of SNF in a DGR.

Betavoltaics (BV) cells (or nuclear batteries) have long-lasting power and high volumetric energy densities that open a broad range of applications that are not currently available, especially in low-power electronics for the internet-of-things, internal medical devices, and harsh environments. The introduction of very low-power electronics has opened up a market for the wide and accepted use of BV cells. As BVs have potentially decades-long useful lifetimes and are anticipated to be used in harsh environments, a method to describe accelerated contact aging has been developed. Monte Carlo radiation simulations show that energy can be deposited in the interface 10-50 times faster than real-world applications. The models can be used to design contact aging experiments for BV cell deployments.

Concentrated solid-solution alloys (CSAs) demonstrate excellent mechanical properties and promising irradiation resistance depending on their compositions. Existing experimental and simulation results indicate that their heterogeneous structures induced by the random arrangement of different elements are one of the most important reasons responsible for their outstanding properties. Nevertheless, the details of this heterogeneity remain unclear. Specifically, which properties induced by heterogeneity are most relevant to their irradiation response? In this work, we scrutinize the role of heterogeneity in CSAs played in damage evolution in different aspects through atomistic simulations, including lattice misfit, thermodynamic mixing, point defect energetics, point defect diffusion, and dislocation properties. Our results reveal that structural parameters, such as lattice misfit and enthalpy of mixing, are generally not suitable to assess their irradiation response under cascade conditions. Instead, atomic-level defect properties are the keys to understand defect evolution in CSAs. Therefore, tuning chemical disorder to tailor defect properties is a possible way to further improve the irradiation performance of CSAs.

Depth-sensing transmission electron microscopic (TEM) in situ mechanical testing has become widely utilized for understanding deformation in irradiated materials. Until now, compression pillars have primarily been used to study the elastic properties and yield of irradiated materials. In this study, we utilize TEM in situ compression pillars to investigate plastic deformation in two ion-irradiated alloys: Fe–9% Cr oxide dispersion strengthened (ODS) alloy and nanocrystalline Cu–24% Ta. We develop an algorithm to automate the extraction of instantaneous pillar dimensions from TEM videos, which we use to calculate true stress–strain curves and strain hardening exponents. True stress–strain curves reveal intermitted plastic flow in all specimen conditions. In the Fe–9% Cr ODS, intermitted plastic flow is linked to strain bursts observed in TEM videos. Low strain hardening or strain softening is observed in all specimen conditions. TEM videos link the strain softening in irradiated Fe–9% Cr ODS to dislocation cross-slip, and in Cu–24% Ta to grain boundary sliding.

Post-irradiation plastic strain spreading in ferritic grains is investigated by means of three-dimensional dislocation dynamics simulations, whereby dislocation-mediated plasticity mechanisms are analyzed in the presence of various disperse defect populations, for different grain size and orientation cases. Each simulated irradiation condition is then characterized by a specific “defect-induced apparent straining temperature shift” (ΔDIAT) magnitude, reflecting the statistical evolutions of dislocation mobility. It is found that the calculated ΔDIAT level closely matches the ductile-to-brittle transition temperature shift (ΔDBTT) associated with a given defect dispersion, characterized by the (average) defect size D and defect number density N. The noted ΔDIAT/ΔDBTT correlation can be explained based on plastic strain spreading arguments and applicable to many different ferritic alloy compositions, at least within the range of simulation conditions examined herein. This systematic study represents one essential step toward the development of a fully predictive, dose-dependent fracture model, adapted to polycrystalline ferritic materials.

Structure–property relationships are the foundation of materials science and are essential for predicting material response to driving forces, managing in-service material degradation, and engineering materials for optimal performance. Elastic, thermal, and acoustic properties provide a convenient gateway to directly or indirectly probe materials structure across multiple length scales. This article will review how using the laser-induced transient grating spectroscopy (TGS) technique, which uses a transient diffraction grating to generate surface acoustic waves and temperature gratings on a material surface, nondestructively reveals the material’s elasticity, thermal diffusivity, and energy dissipation on the sub-microsecond time scale, within a tunable subsurface depth. This technique has already been applied to many challenging problems in materials characterization, from analysis of radiation damage, to colloidal crystals, to phonon-mediated thermal transport in nanostructured systems, to crystal orientation and lattice parameter determination. Examples of these applications, as well as inferring aspects of microstructural evolution, illustrate the wide potential reach of TGS to solve old materials challenges and to uncover new science. We conclude by looking ahead at the tremendous potential of TGS for materials discovery and optimization when applied in situ to dynamically evolving systems.

Highly radioactive waste is incorporated into a glass matrix to convert it into a safe, passive form suitable for long-term storage and disposal. It is currently known that alpha decay can generate gaseous species, which can nucleate into bubbles, either through the production of helium or from ballistic collisions with the glass network that liberate oxygen. An effective method to probe this phenomenon utilizes ion beams to either directly implant helium or investigate the damage due to ballistic collisions. This paper provides an overview of the methodology, summarizes the results of current studies, and draws comparisons between them. We find that the irradiation scheme as well as the temperature and composition of the glass are important in determining whether bubble formation will occur. We also explore how analytical techniques can promote bubble formation and suggest avenues for further work.

Utilizing the experimental and modeling approaches, the Gamma radiation effects on stress responses of the silicon rubber foam under quasistatic compression are investigated. In the experimental work, the samples of the silicon rubber and the silicon rubber foams are quasistatically compressed before and after the Gamma radiation (a dose of 500 kGy and a dose rate of 100 Gy/min). The data reveal that the Gamma radiation obviously increases the material hardness, e.g., the compressive stresses of the silicon rubber and the silicon rubber foams both increase over 5 times as the strain is 20%. In the simulation work, a multiscale method combined with finite element method is developed to numerically predict the compressive stress of the silicon rubber foams. The microscale models are first constructed based on the real microstructures of the silicon rubber foams. The compressive stress and strain relation before and after the Gamma radiation is then simulated and obtained utilizing the phenomenological constitutive models based on the testing data of the silicon rubber. The simulation reveals that the Gamma radiation strongly affects the compressive response of the microscale models. The stress responses of the microscale models are then transferred into the macroscale models. The results also prove that the Gamma radiation obviously increases the hardness of the macroscale models. Data comparison shows that the numerical results agree with the testing data well, which verifies the developed method. The present work develops a new method to predict the radiation effects on mechanical properties of rubber foams.

Irradiation resistance of metallic nanostructured multilayers is determined by the interactions between defects and phase boundaries. However, the dose-dependent interfacial morphology evolution can greatly change the nature of the defect–boundary interaction mechanisms over time. In the present study, we used atomistic models combined with a novel technique based on the accumulation of Frenkel pairs to simulate irradiation processes. We examined dose effects on defect evolutions near zirconium–niobium multilayer phase boundaries. Our simulations enabled us to categorize defect evolution mechanisms in bulk phases into progressing stages of dislocation accumulation, saturation, and coalescence. In the metallic multilayers, we observed a phase boundary absorption mechanism early on during irradiation, while at higher damage levels, the increased irradiation intermixing triggered a phase transformation in the Zr–Nb mixture. This physical phenomenon resulted in the emission of a large quantity of small immobile dislocation loops from the phase boundaries.

Nanocrystalline and nanolaminated materials show enhanced radiation tolerance compared with their coarse-grained counterparts, since grain boundaries and layer interfaces act as effective defect sinks. Although the effects of layer interface and layer thickness on radiation tolerance of crystalline nanolaminates have been systematically studied, radiation response of crystalline/amorphous nanolaminates is rarely investigated. In this study, we show that irradiation can lead to formation of nanocrystals and nanotwins in amorphous CuNb layers in Cu/amorphous-CuNb nanolaminates. Substantial element segregation is observed in amorphous CuNb layers after irradiation. In Cu layers, both stationary and migrating grain boundaries effectively interact with defects. Furthermore, there is a clear size effect on irradiation-induced crystallization and grain coarsening. In situ studies also show that crystalline/amorphous interfaces can effectively absorb defects without drastic microstructural change, and defect absorption by grain boundary and crystalline/amorphous interface is compared and discussed. Our results show that tailoring layer thickness can enhance radiation tolerance of crystalline/amorphous nanolaminates and can provide insights for constructing crystalline/amorphous nanolaminates under radiation environment.

In search of materials with better properties, polycrystalline materials are often found to be superior to their respective single crystalline counterparts. Reduction of grain size in polycrystalline materials can drastically alter the properties of materials. When the grain sizes reach the nanometer scale, the improved mechanical response of the materials make them attractive in many applications. Multicomponent solid-solution alloys have shown to have a higher radiation tolerance compared with pure materials. Combining these advantages, we investigate the radiation tolerance of nanocrystalline multicomponent alloys. We find that these alloys withstand a much higher irradiation dose, compared with nanocrystalline Ni, before the nanocrystallinity is lost. Some of the investigated alloys managed to keep their nanocrystallinity for twice the irradiation dose as pure Ni.

We assess the validity of criteria based on size mismatch and thermodynamics in predicting the stability of the rare class of high-entropy alloys (HEAs) that form in the hexagonal close-packed crystal structure. We focus on nanocrystalline HEA particles composed predominantly of Mo, Tc, Ru, Rh, and Pd along with Ag, Cd, and Te, which are produced in uranium dioxide fuel under the extreme conditions of nuclear reactor operation. The constituent elements are fission products that aggregate under the combined effects of irradiation and elevated temperature as high as 1200 °C. We present the recent results on alloy nanoparticle formation in irradiated ceria, which was selected as a surrogate for uranium dioxide, to show that radiation-enhanced diffusion plays an important role in the process. This work sheds light on the initial stages of alloy nanoparticle formation from a uniform dispersion of individual metals. The remarkable chemical durability of such multiple principal element alloys presents a solution, namely, an alloy waste form, to the challenge of immobilizing Tc.

In this work, we report evidences of the improvement of X-ray attenuation efficiency by the addition of a very small amount of Graphene Oxide (GO) in polymer-based nanocomposite. Poly(vinylidene fluoride) (PVDF) homopolymer and barium sulfate (BaSO4) nanoparticles were mixed. PVDF/BaSO4 nanocomposite was found to attenuate 9.14% of a 20 kV X-ray beam. The addition of only 4.0 wt % of GO nanosheets to the nanocomposite improved this X-Ray attenuation efficiency to 24.56%. The respective linear attenuation coefficients (μ) were 39.9 cm-1 and 54.4 cm-1, respectively. The X-ray attenuation gradually decreases until 6.71% and 17.62%, respectively, for the X-ray beam with higher energy (100 kV). Fourier transform infrared data revealed that, due to the lack of the bending vibration modes of CF2 molecule at 656 cm-1, 688 cm-1, 723 cm-1, 776 cm-1and 796 cm-1, characteristics of the γ-crystalline phase of PVDF, the nanocomposites casted from solution are mostly in the β-ferroelectric phase of PVDF, besides the γ-paraelectric phase. SEM micrographs were used to evaluate the dispersion state of graphene sheets and the BaSO4 nanoparticles into the polymeric matrix. UV-Vis spectrometry and Differential Scanning Calorimetry (DSC) were also performed in order to complement the structural analysis. The results confirm that the addition of graphene sheets in PVDF polymer-based nanocomposites enhances the X-ray shielding efficiency. The phenomenon is discussed in terms of the reported anomalous negative thermal expansion coefficient of graphene sheets

Pristine poly(butylene adipate-co-terephthalate) (PBAT) is a biodegradable aliphatic-aromatic copolyester that shows no photoluminescent features. The radio induction of photoluminescence (PL) properties in PBAT, after exposure to high doses of gamma radiation, was firstly reported in 2014. These new PL properties have great potential for applications at “in vitro” imaging of human cancer, bio-imaging devices and radiation dosimetry. In this paper, we report the radio induction of photoluminescence (PL) properties in PBAT, after exposure to low energy UV irradiation. In this investigation, films of PBAT, produced by the wire-bar coating technique, were exposed to UV radiation for periods of time ranging from 50 to 500 hours. The PL emission analysis revealed that UV irradiation performed under O2 rich air atmosphere enhances the PL output when compared to irradiations performed in the air. FTIR data confirm that the mechanism behind the UV photo-induction of PL features are similar to the mechanism suggested for gamma radio-induction PL emission. The PL intensity x Spectral Irradiance relationship and RGB color components, the green (G) and blue (B) components, can be used to perform 2D UV dosimetry. The high quantum yield emission of UV-induced PL near 500 nm observed in PBAT is a very interesting finding because it involves the development of a new cheap biodegradable photoluminescent polymer that finds application in drug delivery, bio-imaging devices and also in 2D dosimetry.

The photostability of two glycine molecules has been investigated using quantum mechanical methods i.e. at CASSCF/NEVPT2 level theory. It is found that the molecule in water shows vast photostability as a comparison to vacuum. The energies are calculated around HOMO and LUMO orbital. The NEVPT2 computed energies are reasonably matched with experimental results. The study shows that the molecule returns from higher electronically excited states to ground state through CI and AC crossings and these crossings provide a minimum energy path along derivative coupling and gradient differences vector.