Search

Transmission electron microscopy (TEM) was used to compare the microstructural defects produced in an Fe9Cr model alloy during exposure to neutrons, protons, or self-ions. Samples from the same model alloy were irradiated using fission-neutrons, 2MeV Fe+ions or 1.2MeV protons at similar temperatures (∼300°C) and similar doses (∼2.0dpa). The neutron-irradiated alloy contained visible interstitial dislocation loops withb = 111, and on average ∼5 nm in size. The density varied from 2±1 × 1020 m-3(in the matrix far from dislocations and boundaries) to 1.2 ± 0.3 × 1023 m-3(close to helical dislocation lines). Chromium α′-phase precipitates were also identified at a density of 7.4 ± 0.4 × 1023 m-3. Self-ion irradiation produced mostly homogeneously distributed dislocation loops (6–7 nm on average), and with a greater fraction of100loops (∼40%) than was seen in the neutron-irradiated alloy, and at a density of 6.8 ± 0.8 x1022 m-3. In contrast to the loops produced by neutron irradiation, the self-ion irradiated Fe9Cr contained only vacancy-type loops. Chromium also remained in solution. Proton-irradiated Fe9Cr contained interstitial dislocation loops close to helical-dislocation segments, similar to the neutron-irradiated sample. Chromium α′-phases were also identified in the proton-irradiated sample at a density of 2.5 ± 0.3 × 1023 m-3, and large voids (up to 7 nm) were found at a density over 1022m−3. Like the neutron-irradiated sample, the density of dislocation loops was also heterogeneously distributed; far from grain boundaries and dislocation lines the density was 2.5 ± 0.4 x1022 m-3, while close to helical dislocation lines the density was 8.1 ± 1.3 x1022 m-3.

This article describes the radiation facilities and associated sample preparation, management, and analysis equipment currently in place at the Dalton Cumbrian Facility, a facility which opened in 2011 to support the UK’s nuclear industry. Examples of measurements performed using these facilities are presented to illustrate their versatility and the breadth of research they make possible. Results are presented from research which furthers our understanding of radiation damage to polymeric materials, radiolytic yield of gaseous products in situations relevant to nuclear materials, radiation chemistry in light water reactor cooling systems, material chemistry relevant to immobilization of nuclear waste, and radiation-induced corrosion of fuel cladding elements. Applications of radiation chemistry relevant to health care are also described. Research concerning the mechanisms of radioprotection by dietary carotenoids is reported. An ongoing open-labware project to develop a suite of modular sample handling components suited to radiation research is described, as is the development of a new neutron source able to provide directional beams of neutrons.

We have assessed the formation and evolution of void and dislocation arrangements in Ta, Ta-5wt.%W and Ta-10wt.%W as a function of radiation level at a temperature of 345 ± 3 °C, by combining proton irradiation experiments, transmission electron microscopy and nano-hardness measurements. The damaged structure of tantalum at 0.1 dpa is characterized by the presence of a /2 〈111〉 interstitial dislocation loops and randomly distributed voids, whereas only dislocation loops are observed in the two alloys. Void ordering occurs in tantalum at 0.25 dpa, together with the appearance of dense dislocation tangles. A further increase in damage level leads to a continuous nucleation and growth of voids, and saturation is not attained at a damage level of 1.55 dpa. In contrast, the average size and number density of dislocation loops increases gradually with damage level in the two alloys, and voids only form at 1.55 dpa. Tungsten delays the loop evolution and therefore the formation of radiation-induced voids.

The formation of radiation-induced dislocation loops and voids in tantalum at 180(2), 345(3) and 590(5)°C was assessed by 3MeV proton irradiation experiments and subsequent damage characterisation using transmission electron microscopy. Voids formed at 345(3)°C and were arranged into a body centred cubic lattice at a damage level of 0.55 dpa. The low vacancy mobility at 180(2)°C impedes enough vacancy clustering and therefore the formation of voids visible by TEM. At 590(5)°C the Burgers vector of the interstitial-type dislocation loops is a , instead of the a/2 Burgers vector characteristic of the loops at 180(2) and 345(3)°C. The lower mobility of a loops hinders the formation of voids at 590(5)°C up to a damage level of 0.55 dpa.

We have characterised to atomic resolution the mono-layer thick TiO-type precipitate induced by proton irradiation in V-4Cr-4Ti alloy at a dose of 0.3 dpa and a temperature of 350 °C. Its formation coincides with the coarsening radiation-induced interstitial a /2〈111〉 dislocation loops that are already present at 300 °C. The dislocation network induced by prior cold work is mostly recovered at 300 °C and 0.3 dpa, and is therefore expected to exert a minimal effect on the precipitate formation. This monolayer-thick precipitate constitutes an early stage in the radiation-induced aging process of V-4Cr-4Ti at low temperatures, and can potentially absorb additional light elements in reactor environments.

This work investigates the evolution of the tensile and structural properties of fused filament fabrication (FFF), formed polymers under gamma irradiation. Commercial off-the-shelf print filaments of Poly(lactic acid) (PLA), Thermoplastic polyurethane (TPU), Chlorinated polyethylene elastomer (CPE), Nylon, Acrylonitrile butadiene styrene (ABS) and Polycarbonate (PC) were exposed to gamma-ray doses of up to 5.3 MGy. The suitability of FFF-formed components made from these materials for use in radiation environments is evaluated by considering their structural properties. We identify clear trends in the structural properties of all the materials tested and correlate them with changes in the chemical structure. We find that Nylon shows the best performance under these conditions, with no change in ultimate tensile strength and an increase in stiffness. However, some of our findings suggest that the effect of additives to this type of filament may result in potentially undesirable adhesive properties. The organic polymer PLA was notably more radiation-sensitive than the other materials tested, showing 50% decrease in Young’s Modulus and ultimate tensile strength at order of magnitude lower radiation dose. A mechanism is proposed whereby FFF-processed components would have substantially different radiation tolerances than bulk material.

Ion irradiation is a versatile tool to introduce controlled defects into two-dimensional (2D) MoS2 on account of its unique spatial resolution and plethora of ion types and energies available. In order to fully realise the potential of this technique, a holistic understanding of ion-induced defect production in 2D MoS2 crystals of different thicknesses is mandatory. X-ray photoelectron spectroscopy, electron diffraction and Raman spectroscopy show that thinner MoS2 crystals are more susceptible to radiation damage caused by 225 keV Xe+ ions. However, the rate of defect production in quadrilayer and bulk crystals is not significantly different under our experimental conditions. The rate at which S atoms are sputtered as a function of radiation exposure is considerably higher for monolayer MoS2, compared to bulk crystals, leading to MoO3 formation. P-doping of MoS2 is observed and attributed to the acceptor states introduced by vacancies and charge transfer interactions with adsorbed species. Moreover, the out-of-plane vibrational properties of irradiated MoS2 crystals are shown to be strongly thickness-dependent: in mono- and bilayer MoS2, the confinement of phonons by defects results in a blueshift of the A 1 g mode. Whereas, a redshift is observed in bulk crystals due to attenuation of the effective restoring forces acting on S atoms caused by vacancies in adjacent MoS2 layers. Consequently, the A 1 g frequency of tri- and quadrilayer crystals is statistically invariant on account oft competition between phonon confinement effects and interlayer interactions. The A 1 g linewidth is observed to decrease in bi- and trilayer crystals after low dose irradiation and is attributed to layer decoupling. This work shows that there is a complex interplay between defect production, crystal thickness and interlayer interactions in MoS2. Our results demonstrate that ion irradiation is an effective tool to modulate the electronic, vibrational and structural properties of MoS2, which may prove beneficial for practical applications.

We have developed a new irradiation facility that allows to perform accelerated damage tests of nuclear reactor materials at temperatures up to 400 °C using the intense proton (

With the announcement of the U.K. new nuclear build and the requirement to decommission old facilities, researchers require bespoke facilities to undertake experiments to inform decision making. This paper describes development of The University of Manchester’s Dalton Cumbrian Facility, a custom built research environment which incorporates a 5 MV tandem ion accelerator as well as a self-shielded 60 Co irradiator. The ion accelerator allows the investigation into the radiolytic consequences of various charged particles, including protons, alpha particles and a variety of heavier (metal and nonmetal) ions, while the 60 Co irradiator allows the effects of gamma radiation to be studied. Some examples of work carried out at the facility are presented to demonstrate how this equipment can improve our mechanistic understanding of various aspects of the deleterious effects of radiation in the nuclear industry. These examples include applications in waste storage and reprocessing as well as geological storage and novel surveying techniques. The outlook for future research is also discussed.

The residual stress distributions in oxide dispersion-strengthened steel plates, joined by Friction Stir Welding, have been mapped using neutron diffraction. The measured stress maps were interpreted in terms of the temperature profiles measured for welds using three different tool traverse speeds. The largest peak longitudinal tensile stresses, ∼1200 MPa, were found in the weld produced using the fastest tool traverse speed, and corresponds to relatively high cooling rates. A reduction in tool traverse speed yields a significant decrease in tensile residual stresses in the thermo-mechanically affected zone of the welds, but also causes higher peak temperatures during welding. The transverse residual stresses were not found to be affected by the tool traverse speed and were significantly lower in magnitude than the longitudinal stresses. Additionally, the torque profiles measured during welding increased with the amount of material stirred and therefore correlated with the width of the thermo-mechanically affected zone of the welds.