Introducing a radioactive nuclide into the appropriate targeting vector allows to diagnose the biochemical correlates of many diseases, or to selectively ablate tumor cells; such capability is steadily growing its impact in clinical practices. However, many of the medically useful radionuclides are produced within fission reactors, followed by complex and costly processing, limiting accessibility and increasing cost of such treatments. In this work we investigate the potential of using the highly energetic neutrons (14.06 MeV) from nuclear fusion reactions to promote the production of known, prospected or novel radionuclides of medical interest. We interrogated nuclear reaction databases to filter the most efficient neutron reactions, and obtained a list of potential products, from which we further selected the ones with the greatest potential medical relevance. A subset of 43 radionuclides was identified, for both imaging and therapy, and with differing carrier status. Among them, we identified 47Sc, 67Cu, 99Mo, and alpha emitters 212Pb and 225Ac, as some of the current isotopes that could be produced efficiently from fusion neutrons. We also highlight some promising novel radionuclides, such as 189Ir and 84Rb for imaging, and 114mIn, 161Ho, 165Er and 169Er for therapy. In addition, we estimate that D-T nuclear fusion reactors can also provide access to energetic protons or moderated neutrons, thus providing backup options to cyclotrons and fission reactors. Our findings pave the way to introducing a greener, safer, possibly cheaper, radionuclide production pathway using fusion reactors.

Reported β phase fractions in equiaxed Ti-6Al-4V (Ti-64) commonly exceed 10%, despite equilibrium predictions of ∼4%. Here we demonstrate that this discrepancy arises primarily from non-equilibrium partitioning during cooling from the α+β regime. Reducing the cooling rate from 1°C/min to 0.1°C/min decreases the measured β fraction by up to 92% in Ti-64, yet equilibrium is still not achieved. Similar behaviour is observed in Ti-5Al-7.5V (Ti-575). Elemental analysis reveals substantial redistribution of vanadium with slower cooling, confirming diffusion-limited β phase evolution. Comparison of EBSD, BSE imaging, and XRD shows measurement deviations within ±2%, insufficient to explain the literature spread. CALPHAD predictions agree with Ti-64 equilibrium behaviour but fail for Ti-575, highlighting strong sensitivity to small compositional variations, particularly aluminium content. These results demonstrate that commonly reported “equiaxed” microstructures in two-phase Ti alloys are kinetically constrained and may significantly overestimate equilibrium β fractions.

Neutron irradiation of commercial Zr alloys containing Sn, Nb and Fe induces the formation of microstructural features, including point defect clusters, dislocation loops and precipitate phases. The distribution and interactions of alloying elements and defects in alpha-Zr are crucial for predicting microstructural evolution and mechanical degradation in these alloys. Density functional theory (DFT) simulations are performed to assess interactions among point defect clusters in the HCP Zr lattice. This study examines the energy and configuration of clusters comprising Sn, Nb, Fe and vacancies, considering sizes up to quadruplets of point defects. Both shortrange and long-range interactions are observed in Sn-Fe and Nb-Fe clusters at different sizes. In addition to binding energies, a many-body interaction term is determined to quantify the inaccuracies inherent in the defect pair models commonly used in kinetic Monte Carlo simulations, which account for the attractive or repulsive effects introduced by the additional third or fourth defect. Many-body interactions in defect clusters in the HCP lattice are found to be more dependent on the specific atomic configuration of the defects than the quantity of certain defects. Notably, for Nb-dominated clusters, pairwise assumptions show no significant difference from the exact triplet binding energies.

Compositionally complex materials (CCMs) have received significant interest in the nuclear materials community due to their perceived radiation damage tolerance. However, the effects of elemental mixing on radiation attenuation in CCMs, which directly impacts the materials performance in nuclear applications, has often been overlooked. By applying new radiation transport physics methods to CCMs we unveil two new neutronic "cocktail effects" that arises from the isotopic dependence and non-linear nature of neutron interactions, which leads to improved neutronic performance of CCMs compared to conventional materials in bulk or layered form. The two new cocktail effects that have been discovered and mathematically proved are: (1) mixing compounds with opposing scattering and absorbing ratios increases radiation attenuation as more particles are readily scattered into the absorbing atoms; (2) because the atomic density is typically not conserved when mixing compounds, the previous effect can be magnified, or reduced, by concentrating or diluting the neutronically beneficial elements. These cocktail effects arise regardless of whether the CCM is single- or multi-phase, provided the microstructural length scale is smaller than the mean free paths of neutrons within the material. The findings may be applied to either enhancement of attenuation of a material (e.g. shielding) or to minimise it (e.g. in-core reactor components). The new discovery is used to identify high entropy borides with enhanced shielding performance compared to the fusion industry best standard (WB2) and lower material cost simultaneously. Even stronger performance can be obtained with hydrides. In general, ceramics, and in particular hydrides, tend to attenuate more strongly then metallic alloys due to their high atomic densities, and the effect is often strongest with higher non-metal/metal stoichiometric ratios. These findings open the door to the design of novel CCMs for emerging technologies which have improved radiation transport properties, lower costs, and/or reduced reliance on critical minerals.

Suprathermal fusion reactions, initiated by energetic particles slowing down and scattering in dense plasmas, can modify the burn dynamics at inertial confinement fusion (ICF) regimes. A 0D time-dependent Monte-Carlo code has been developed to assess the suprathermal energy gain from fast fusions in DT, deuterium, ^11BH_3 and ^11BHDT fuels. It incorporates modified Li-Petrasso stopping powers, thermal broadening of cross-sections, anisotropic nuclear elastic and neutron elastic scattering, and a physical model for the p^11B alpha-particle spectra. Results show that earlier predictions of suprathermal criticality in pure deuterium are overestimated by more than an order of magnitude; no realistic density-temperature regime supports a self-sustaining chain reaction. Only DT demonstrates a critical regime provided there is no neutron leakage. Fast protons in ^11BH_3 have an optimum energy of 4 MeV for maximising suprathermal enhancement. In this case the additional energy from fast fusions is unlikely to exceed 40

An ideal water-splitting electrocatalyst is inexpensive, abundant, highly active, stable, selective, and durable. The anodic oxygen evolution reaction (OER) is the main bottleneck for H-2 production with a complex and not fully resolved mechanism, slow kinetics, and high overpotential. Nickel oxide-based catalysts (NiOx) are highly active and cheaper than precious metal catalysts. However, rigorous catalyst tests and DFT calculations are still needed to rationally optimize NiOx catalysts. In this work, we combine plasma-enhanced atomic layer deposition (PE-ALD) and density functional theory (DFT) to address the role of dopants in promoting NiOx OER activity. Ultrathin films of NiOx doped with Zn2+, Al3+, and Sn4+ presented improved intrinsic activity, stability, and durability for the OER. The results show a low to high catalytic performance of ZnNiOx < NiOx < AlNiOx < SnNiOx, which we attribute to an increase in the concentration of valence band (VB) holes combined with conduction band (CB) electron conductivity, characterized by electrochemical impedance spectroscopy (EIS). The influence of doping on the electronic structure and catalytic activity was investigated using advanced characterization techniques and density functional theory (DFT) calculations (PEB0/pob-TZVP). DFT complements the experimental results, showing that the dopant charge states and orbital hybridization enhance the OER by improving the charge carrier concentration and mobility, thus allowing optimal binding energies and charge dynamics and delocalization. Our findings demonstrate the potential of PE-ALD-doped nanofilms NiOx and DFT to rationally design and develop catalysts for sustainable energy applications.

The diffusion of boron (VB) and tungsten vacancies (VW) in the hypo-stoichiometric epsilon-phase of tungsten boride was studied using an Atomic (Lattice) Kinetic Monte Carlo (AKMC) approach, informed by Density Functional Theory (DFT) simulations. To account for the hypo-stoichiometric nature of the epsilon-phase, two limiting compositions, B-poor and B-rich, were considered. Results showed that both VB and VW exhibit strong anisotropic behaviour, with basal migration requiring significantly less energy than c-axis migration. Consequently, diffusion coefficients for both vacancies are orders of magnitude smaller in the c-direction regardless of B stoichiometry, indicating a predominance of 2D diffusion. This behaviour impacts the evolution of radiation-induced defects, potentially leading to anisotropic swelling. While the basal diffusivity of VB remains largely unaffected by the stoichiometry, its c-axis diffusivity is found to be highly sensitive to boron content, which enhances vacancy migration through additional pathways. Although diffusion is found to be faster in the basal planes, increased boron occupancy slightly reduces the level of anisotropy, a trend that also diminishes at higher temperatures. Nonetheless, the VB diffusion remains significantly anisotropic, exceeding a factor of 100 even at extreme temperatures. These findings underscore the critical role of stoichiometry in regulating vacancy behaviour and promoting densification, which is essential for optimizing tungsten boride materials in compact fusion reactor applications.

Zirconium (Zr) alloys, such as Zircaloy-4, are widely used for structural components and fuel cladding in industrial nuclear fission applications. High-pressure torsion (HPT), a severe plastic deformation process, produces an ultra-fine grain structure with properties that may have benefits in the nuclear industry, but the microstructural implications of processing of Zr alloys using this technique have not yet been extensively explored. Here, electron microscopy and atom probe tomography were used to investigate the microstructure and solute distribution in an as-received Zircaloy-4 and a fine-grained HPT-processed sample. Fe segregates to grain boundaries in both samples, however, at much lower concentrations after HPT processing, indicating that Fe diffuses to the newly formed grain boundaries during the severe plastic deformation. Although Sn segregates to the grain boundaries of the as-received sample, it is distributed almost homogenously in the HPT-processed sample, which may provide advantages for corrosion resistance. Very low concentrations of Cr alloying elements at the matrix and grain boundaries of both samples are attributed to precipitation.

The growth of Fe on a clean Be(0001) surface is investigated on the atomic scale by a combined scanning tunneling microscopy and density functional theory study. At low Fe coverage, the nucleation of terraced nanoislands with a disordered surface is observed experimentally. Increasing the Fe coverage results in the growth of extended films exhibiting a well-ordered p(2x 2) superstructure. Density functional theory is applied to investigate the growth of Fe on a Be(0001) surface from individual atoms to extended films. Our studies provide strong evidence for the formation of a buckled honeycomb Fe lattice that is embedded in two Be planes with Kagome and triangular symmetry, respectively.

Zirconium (Zr) alloys, such as Zircaloy-4 (Zy-4), are widely used for cladding in nuclear applications. Zy-4 consists of an alpha-Zr matrix and various second phase particles (SPPs). These precipitates play a crucial role in determining the overall alloy performance, so understanding their composition is essential for the development of these nuclear materials. We have studied two SPPs in this alloy, Zr(Fe,Cr)2 and Zr2(Si,Fe), using site-specific focused ion-beam lift-out and atom probe tomography, and measured the composition and distribution of alloying elements at the precipitate/matrix interface. Residual Cu and B segregated to the interfaces of both precipitates and the matrix while Sn only segregated to the interface in the Zr2(Fe,Si) precipitate. Hydrogen segregation was observed at the interface of Zr(Fe,Cr)2 and the matrix.

The accurate chemical composition of second phase particles (SPPs) and solute distributions at grain boundaries and interfaces are still not known for Optimised ZIRLO, with recent debate over the identification of a Zr-Nb-Fe intermetallic phase in these alloys. Here, atom probe tomography (APT) is combined with scanning transmission electron microscopy (STEM), transmission Kikuchi diffraction (TKD), and density functional theory (DFT) to demonstrate that the phase, commonly reported as Zr(Nb,Fe)(2), is most likely an intermetallic phase of (Zr,Nb)(3)Fe with similar to 35 at.% Nb. Interfacial excess is calculated at the beta-Nb/alpha-Zr and (Zr,Nb)(3)Fe/alpha-Zr interfaces and at the grain boundaries. Fe is enriched at the interface between beta-Nb precipitates and the alpha-Zr matrix. Fe, Sn, and Nb segregate at alpha-Zr grain boundaries, no Sn segregation was observed at the interface of beta-Nb/alpha-Zr matrix, and slight Sn segregation was detected at the interface of the intermetallic phases with the alpha-Zr and at the grain boundaries. An enhanced understanding of grain boundary segregation, secondary phases composition, and solute behaviour will inform a better understanding of mechanical and corrosion properties, which is expected to be useful for future Zr alloy development.

The steam oxidation of Cr-doped UN fuel pellets is analysed during sequential isothermal holds up to 720 degrees C. In situ neutron diffraction results show how Cr is accommodated in a secondary U2CrN3 phase, leading to the formation of a duplex UN/U2CrN3 microstructure. Under corrosion, the oxidation of the two phases begins at 400 degrees C for UN and 430 degrees C for U2CrN3, respectively. Because the UN phase is preferentially oxidised in the presence of U2CrN3, addition of Cr in UN based nuclear fuel is found to accelerate the corrosion rate. At 430 degrees C the oxidation of UN in the UN/U2CrN3 microstructure is similar to 5 times faster than pure UN, increasing to similar to 19 times faster at 460 degrees C. The oxidation of U2CrN3 produces UO2 via the formation of two transient intermediate phases. In situ neutron diffraction enables oxidation processes of UN and U2CrN3 components to be followed separately within the two-phase system.

The c-phase of the tungsten boride (W-B) system is investigated for its use as a high energy neutron shielding material in compact spherical tokamak reactors. The determination of accurate phase boundaries for this system is particularly important to fusion energy technology, because B concentration will have a decisive influence on shielding performance and lifetime. Three W-B compositions from both W and B excess peripherals of the c-phase were produced from metallic W and isotopically enriched 11B by arc melting to investigate the stoichiometric range of the c-phase and phase evolution pathways in both as-solidified and homogenised conditions. The B concentration of the c-phase in W-excess and B-excess samples are reported, along with their crystallographic space group, site coordinates, and B occupancies, as determined by neutron powder diffraction and complementary scanning electron microscopy and X-Ray diffraction characterisation. As determined by Rietveld refinement, the c-phase has a significantly lower B-concentration and compositional range than previously reported, of between 63.8 and 64.1 at%. Neutron diffraction data show that the B deficiency is accommodated almost entirely by B vacancy at the 2a crystallographic site. The lattice parameters of the c-phase in the excess-B samples are smaller than those of the W-excess sample. A revised W-B phase diagram is proposed to take account these new measurements.

This study employs molecular dynamics (MD) simulations and lattice dynamics (LD) calculations to investigate the superionic transition in UO2, as well as the characteristics of the superionic phase. The superionic transition is found to be a second-order phase transition associated with an inflection point in enthalpy and lattice parameter at 2600 K. This resembles displacive phase transitions and is associated with an oxygen vibration mode becoming imaginary. The superionic state shows a combination of different local environments and dynamic features similar to glass-forming liquids. The analysis of its dynamics reveals seemingly contradictory characteristics: properties follow those of the lower-temperature crystalline phase in some respects, while exhibiting liquidlike behavior in others. The study highlights the complexity of the superionic phase, including heterogeneous mobility and diffusion mechanisms involving stringlike anion clusters.

The steam oxidation resistance of UN and UN-(20 vol%)ZrN fuel pellets is evaluated to enhance understanding of steam corrosion mechanisms in advanced nuclear fuel materials. In situ neutron diffraction shows the modified UN fuel pellets form a (U-0.77,Z(r0.23))N solid-solution and the sole crystalline oxidation product detected in bulk is (U-0.77,Zr-0.23)O-2. U(2)N(3 )is not detected in significant quantities during the steam oxidation of UN or (U-0.77,Zr-0.23)N and stable lattice parameters show that hydriding does not take place. Steam oxidation rates, obtained via sequential Rietveld refinement show how (U-0.77,Zr-0.23)N has a higher activation energy (79 +/- 1 kJmol(- 1) vs. 50 +/- 5 kJmol(- 1)), higher onset temperature (430 C-degrees vs. 400 C-degrees) and slower reaction rates for steam oxidation up to 616 C-degrees, than pure UN. Throughout, both UN and (U-0.77,Zr-0.23)N exhibit linear (non-protective) oxidation kinetics, signifying that degradation of the fuel pellets is caused by the evolution of gaseous products at the interface followed by oxide scale spallation. This quantitative and mechanistic understanding of material degradation enables better defined operating regimes and points towards (U,Zr)N solid solutions as a promising strategy for the design of advanced nuclear fuel materials with enhanced steam corrosion resistance.

Zirconium (Zr) alloys, such as Zircaloy-4 (Zy-4), are widely used for cladding in nuclear applications. Zy-4 consists of an α-Zr matrix and various second phase particles (SPPs). These precipitates play a crucial role in determining the overall alloy performance, so understanding their composition is essential for the development of these advanced nuclear materials. We have studied two SPPs in this alloy, Zr(Fe,Cr)2 and Zr2(Si,Fe), using site-specific focused ion-beam lift-out and atom probe tomography, and measured the composition and distribution of alloying elements at the precipitate/matrix interface. Residual Cu and B segregated to the interfaces of both precipitates and the matrix while Sn only segregated to the interface in the Zr2(Fe,Si) precipitate. Hydrogen segregation was observed at the interface of Zr(Fe,Cr)2 and the matrix.

This study investigates the morphology and composition of hydrides in Optimized ZIRLO following electrochemical deuterium charging. Both ZrO and ZrDx phases were formed upon charging. The interfaces between these phases are investigated by using atom probe tomography aided by cryogenic sample transfer. The Ga and Sn have formed a “net”-like structure at the original atom probe specimen surface, which is assumed to be associated with the boundaries between individual hydride laths/needles, as it thought to have formed as these species were excluded from the hydrides. Calculation of the D/Zr ratio throughout the sample allows for identification of the ZrDx phases, revealing the specimen consists of a complex arrangement of different hydride phases. In some areas there is small excess of D in the hydride, i.e. ZrD2+y. This result is interpreted as deuterium which was “frozen” as it was passing through the hydride during electrochemical charging. The observed microstructural changes and interfacial phenomena contribute valuable insights that may prove useful for improving the performance and safety of Zr alloys.

Hydrogen-induced degradation of pipeline steels is a serious safety challenge for the transport of hydrogen. Steel pipes contain a large proportion of the pearlite phase, which consists of lamellar cementite in ferrite. How hydrogen interacts with pearlite and degrades the mechanical properties remains unclear. Here we have studied the deformation behavior of pearlite in the presence of hydrogen. In-situ micromechanical results revealed that H softens the pearlite. Uncharged samples deform by slip at the ferrite-cementite interface, while deformation in Hcharged pearlitic samples occurs predominantly via slip within the ferrite phase, with some shearing of the cementite. Cryo atom probe tomography confirms that hydrogen is associated with defects in the ferrite, away from the interface, and is trapped within the cementite, which is thought to be the result of a high concentration of C vacancies. Hydrogen is not observed at the ferrite-cementite interface. First principal simulations show that the expected influence of lattice strain and cementite vacancies on hydrogen trapping is consistent with the experimental results. The softening is attributed to a reduction in the energy required for dislocation motion in both the ferrite and the cementite.