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We performed tomographic investigation of the most heavily perturbed (thus highly radioactive) rod and its pristine/unirradiated replicate from the target No. 12 of the Swiss neutron spallation source (SINQ). The tomographic dataset reveals the 3D re-distribution of the lead filling inside the irradiated Zircaloy tube. The change in the linear attenuation coefficient of both the lead filling and the Zircaloy tube of the irradiated rod (due to the presence of the entrapped spallation products) in comparison with the pristine/unirradiated material is quantified. The dataset provides valuable input for the enhancement of safety and efficiency of future spallation targets at SINQ.

Digital fabrication methods with concrete have been rapidly developing, with many problems related to component production and material control being solved in recent years. These processes produce inherently layered cementitious components that are anisotropic, and in many cases, produces a weak interface between layers, which are generally referred to as cold joints. While material strength at these interfaces has been well studied in recent years, durability has received less attention, even though cold joints can function as channels for aggressive agents, such as chlorides. This work presents a method using micro-X-ray fluorescence (μXRF) to image chloride ingress into layer interfaces of 3D printed fine-grained concrete specimens produced with varying layer deposition time intervals, and also compares it to neutron imaging of moisture uptake. The results show that cold joints formed after a 1 day time interval are highly susceptible to chloride ingress, and that curing conditions play a major role in how quickly interfacial transport can take place. The μXRF method is also shown to be useful for study of transport of chlorides in cold joints, due to its spatial resolution and direct analysis of an aggressive species of interest., Materials and Structures, 56 (3), ISSN:1359-5997, ISSN:0025-5432, ISSN:1871-6873

Heterogeneous catalysts are materials with a complex structure at the atomic to mesoscopic scale, which depends on a variety of empirical parameters applied during preparation and processing. Although model systems clarified the general physical and chemical phenomena relevant to catalysis, such as hydrogen spillover, a rational design of heterogeneous catalysts is impeded by the sheer number of parameters. Combinatorial methods and high-throughput techniques have the potential of accelerating the development of optimal catalysts. We describe here a combinatorial approach based on hydrogen adsorption/absorption and hydrogen-deuterium exchange quantified by neutron imaging. The method coined CONI is capable of measuring more than 50 samples simultaneously. As a proof of concept, we study Pt catalyzed WO

Fast neutron imaging is a nondestructive technique for large-scale objects such as nuclear fuel rods. However, present detectors are based on conventional phosphors (typically microcrystalline ZnS:Cu) that have intrinsic drawbacks, including light scattering, γ-ray sensitivity, and afterglow. Fast neutron imaging with colloidal nanocrystals (NCs) was demonstrated to eliminate light scattering. While lead halide perovskite (LHP) FAPbBr3 NCs emitting brightly showed poor spatial resolution due to reabsorption, the Mn2+-doped CsPb(BrCl)3 NCs with oleyl ligands had higher resolution because of large apparent Stokes shift but insufficient concentration for high light yield. In this work, we demonstrate a NC scintillator that features simultaneously high quantum yields, high concentrations, and a large apparent Stokes shift. In particular, we use long-chain zwitterionic ligand capping in the synthesis of Mn2+-doped CsPb(BrCl)3 NCs that allows for attaining very high concentrations (>100 mg/mL) of colloids. The emissive behavior of these ASC18-capped NCs was carefully controlled by compositional tuning that permitted us to select for high quantum yields (>50%) coinciding with Mn-dominated emission for minimal self-absorption. These tailored Mn2+:CsPb(BrCl)3 NCs demonstrated over 8 times brighter light yield than their oleyl-capped variants under fast neutron irradiation, which is competitive with that of near-unity FAPbBr3 NCs, while essentially eliminating self-absorption. Because of their rare combination of concentrations above 100 mg/mL and high quantum yields, along with minimal self-absorption for good spatial resolution, Mn2+:CsPb(BrCl)3 NCs have the potential to displace ZnS:Cu as the leading scintillator for fast neutron imaging.

Supercooling of liquids leads to peculiarities which are scarcely studied under high-pressure conditions. Here, we report the surface tension, solubility, diffusivity, and partial molar volume for normal and supercooled liquid solutions of methane with p-xylene. Liquid bodies of perdeuterated p-xylene (p-C8D10), and, for comparison, o-xylene (o-C8D10), were exposed to pressurized methane (CH4, up to 101 bar) at temperatures ranging 7.0–30.0 °C and observed at high spatial resolution (pixel size 20.3 μm) using a non-tactile neutron imaging method. Supercooling led to the increase of diffusivity and partial molar volume of methane. Solubility and surface tension were insensitive to supercooling, the latter substantially depended on methane pressure. Overall, neutron imaging enabled to reveal and quantify multiple phenomena occurring in supercooled liquid p-xylene solutions of methane under pressures relevant to the freeze-out in the production of liquefied natural gas.

Summary The spatiotemporal distribution of multiple components and phases governs their evaporation and condensation at the liquid-vapor interface. However, in situ methods to characterize the distribution remain challenging, despite the significance of understanding the ubiquitous mass transport phenomena. Here, we introduce high-resolution neutron imaging as a versatile method to quantify the composition of a sessile droplet in situ, under evaporation and condensation. To prove the concept, we perform a neutron transmittance analysis of a sessile heavy water (D2O) droplet and measure the fraction change of H2O to D2O by the sorption of ambient H2O vapor during the evaporation. Our observations are consistent with ex situ Fourier transform infrared spectroscopy measurements and our diffusion-based numerical model. Our results demonstrate that, with deuterated components having a physicochemical similarity with their hydrogenated counterparts, high-resolution neutron imaging can trace composition changes in nonequilibrium phenomena, such as evaporation and condensation.

This paper demonstrates particle tracking velocimetry performed for a model system wherein particle-laden liquid metal flow about a cylindrical obstacle was studied. We present the image processing methodology developed for particle detection in images with disparate and often low signal- and contrast-to-noise ratios, and the application of our MHT-X tracing algorithm for particle trajectory reconstruction within and about the wake flow of the obstacle. Preliminary results indicate that the utilized methods enable consistent particle detection and recovery of long, representative particle trajectories with high confidence. However, we also underline the necessity of implementing a more advanced particle position extrapolation approach for increased tracking accuracy. We also show that the utilized particles exhibit the Stokes number range that suggests good flow tracking accuracy, and that the particle time scales extracted from reconstructed trajectories are consistent with expectations based a priori estimates.

Flotation is an important process in liquid-solid and solid-solid separation, whereby desired solids in suspensions are recovered by their attachment to gas bubbles. Monitoring the process is essential for increased grade of quality and reduced water consumption. However, in situ measurements of the froth’s phases (liquid, air, particles) or volume flow, which is easily integrable in industrial process are not available. In this paper, we propose an instrumentation with ultrasound transducers of center frequency of 135 kHz and electrodes to measure the liquid fraction distribution in foam and froth with high spatio-temporal resolution of 6.65 mm (axial), 13 mm (lateral) and 1 Hz. The measurement system was calibrated in homogeneous, steady foam by an integral conductivity measurement. A backscatter model was applied to reduce the effect of ultrasound shadowing and enhance quantitative liquid fraction estimates. The measurement was validated by neutron radiography. An averaged absolute and relative measurement uncertainty of 0.17 ·10 −2 and 35.1 % for 1 s and 0.08 ·10 −2 and 17.2 % for 100 s measurement was achieved respectively. As an additional validation six cases of inhomogeneous and dynamic liquid fraction distributions were investigated qualitatively. We were able to determine the liquid fraction in froth in a spatially and temporally resolved manner with a penetration depth of 9.2 cm. This investigation distinguished between two of the three froth phases within the analyzed range. However, only processes with low liquid fraction (≤ 0.83 ·10 −2 ) can be monitored. This work be considered a a first step towards in situ monitoring of froth flotation processes.

High-resolution neutron imaging is difficult, due to the low-light output of neutron scintillators, and the spread of light within common neutron-sensitive scintillators as well as the spread of intermediate particles occurring during the detection process. To address this issue, we have developed a high-resolution scintillator for neutron imaging by combining enriched 10B with the well-known CsI:Tl scintillator films. CsI:Tl has excellent properties for X-ray imaging applications, due to a high light yield of 60 000 photons/MeV, and high spatial resolution, which derives from its microcolumnar structure, which channels scintillation light to the photodetector. To enable CsI:Tl to detect neutrons, 10B (96% enriched) was deposited by electron beam directly onto the CsI:Tl film, making a layered scintillator structure in which the alphas produced by the neutron interaction with 10B are detected in the CsI:Tl. The 10B layer was approximately $3~\mu \text{m}$ thick, while the thickness of the CsI:Tl film was $11~\mu \text{m}$ . These novel layered scintillators were integrated into the high-resolution neutron imaging detector [“Paul Scherer Institute (PSI) Neutron Microscope”] at the Pulse OverLap DIffractometer (POLDI) beamline at the PSI. With our 10B/CsI:Tl scintillator, we were able to achieve a spatial resolution down to $9~\mu \text{m}$ . To demonstrate the effectiveness of the layered scintillator, we present results obtained by thermal neutron imaging as well as high-resolution neutron-computed tomography. Finally, we believe there is considerable scope for future optimization of the performance of this system.

The fuel rod claddings in nuclear light water reactors are made of zirconium alloys. Corrosion of these alloys during operation and in particular high temperature oxidation during nuclear accidents results in the production of free hydrogen. The cladding can absorb this hydrogen. It affects the mechanical properties of the cladding material. Hydrogen embrittlement of these materials provides the risk of brittle fracture of the cladding by thermo-shock during emergency cooling. At KIT the behaviour of cladding materials under different hypothetical nuclear accident scenarios was investigated. One focus was on hydrogen absorption and distribution/re-distribution in the alloys. The hydrogen distribution was determined mainly by neutron tomography. Examples for the determination of the 3D hydrogen distribution in cladding tubes after loss of coolant accident simulation tests are given and discussed.

We demonstrate a simple single grating beam modulation technique, which enables the use of a highly intense neutron beam for differential phase and dark-field contrast imaging and thus spatially resolved structural correlation measurements in full analogy to interferometric methods. In contrast to these interferometric approaches our method is intrinsically achromatic and provides unprecedented flexibility in the choice of experimental parameters. In particular the method enables straight forward application of quantitative dark-field contrast imaging in time-of-flight mode at pulsed neutron sources. Utilizing merely a macroscopic absorption mask unparalleled length scales become accessible. We present results of quantitative dark-field contrast imaging combining microstructural small angle scattering analyses with real space imaging for a variety of materials.

Just after the start into the new millennium the concept for combined neutron and X-ray imaging was introduced by extending the standard configuration of the thermal neutron imaging NEUTRA instrument with a complementary 320 kV X-ray tube setup. Using essentially the same detector configuration for both neutron and X-ray imaging enables a pixel-wise (in radiography) and a voxel-wise (in tomography) correlation and combination of attenuation data. The optimal use and analyses of such complementary data sets depend on the specific investigation and research question and range from a combinatory interpretation of separately analyzed images to full data fusion approaches. Here, several examples from more than a decade of bimodal neutron and X-ray imaging at NEUTRA at PSI shall be reviewed.

Hydrogels are normally isotropic and weak, in contrast to their natural analogs that possess hierarchically oriented structure and excellent mechanical properties. Inspired by the unique structure of natural materials, we develop an approach for preparing highly anisotropic hydrogels with programmable oriented polymer structure and extraordinary mechanical properties. Our method is based on a novel welding technique for stretched cellulose hydrogel films, in which interfacial reconfiguration occurs, allowing full integration without compromising the highly aligned polymer orientation. We demonstrate the versatility of this method by fabricating four types of anisotropic tough multilayer hydrogels with differently oriented hierarchies: parallel lamination (‖), orthogonal lamination (⊥), axial rolling, and concentric rolling. These high-water-content hydrogels (∼68 wt%) exhibit extremely high anisotropy (birefringence ≥0.006, the highest reported for hydrogels) and superior mechanical properties (Young's modulus of ∼140 MPa, tensile strength of ∼47 MPa, and work of extension of ∼20 MJ m−3). Moreover, these hydrogels also show interesting anisotropic electrical conductivity and asymmetric shape deformation. Because this method is easy to apply and offers flexibility in designing complex hierarchical hydrogel structures, our work opens a new window to designing novel hydrogel materials for engineering and biomedical applications.

This paper reports on light yield enhancement of terbium-doped gadolinium oxysulfide based scintillator screens achieved by coating their substrates with thin layers of a high density and high atomic number material. For this purpose, iridium was chosen and layers of various thicknesses were applied by atomic layer deposition (ALD). We assessed newly developed scintillator screens for neutron absorption, light yield and spatial resolution and compared them to previously used non-iridium-coated scintillator screens. The addition of the iridium layer resulted in 65 % light yield enhancement in comparison to uncoated scintillator screens while the spatial resolution and absorption power remained unchanged., MethodsX, 6, ISSN:2215-0161

NEURAP is a dedicated set-up at the Swiss neutron spallation source (SINQ) at the Paul Scherrer Institut (PSI), optionally implemented as a special configuration of the neutron-imaging station NEUTRA. It is one of very few instrumentations available worldwide enabling neutron-imaging of highly radioactive samples to be performed routinely, with special precautions and following a specific procedure. Since the relevant objects are strong γ-sources, dedicated techniques are needed to handle the samples and to perform neutron-imaging despite the radiation background. Dysprosium (Dy)-loaded imaging plates, effectively made sensitive to neutrons only, are employed. Neutrons are captured by Dy during neutron irradiation. Then the imaging plate is erased removing gamma detections. A subsequent relatively long self-exposure by the radiation from the intrinsic neutron-activated Dy within the imaging plate yields the neutron-only radiograph that is finally read out. During more than 20 years of NEURAP operation, images have been obtained for two major applications: (a) highly radioactive SINQ target components were investigated after long-term operation life; and (b) spent fuel rods and their cladding from Swiss nuclear power plants were characterized. Quantitative analysis of the image data demonstrated the accumulation of spallation products in the lead filled “Cannelloni” Zircaloy tubes of the SINQ target and the aggregation of hydrogen at specific sites in used fuel pins of power plants and their cladding, respectively. These results continue to help understanding material degradation and optimizing the operational regimes, which might lead to extending the safe lifetimes of these components.

In metallurgical processing, non-metallic inclusions contaminating metallic materials are one highly relevant challenge. Bubble injection into molten metals boosts the inclusion control and removal, thus enhancing metal homogenisation and purification. Although this principle of bubble flotation has been used for a long time, the effects of bubble–inclusion interactions in molten metals are not yet well researched. Imaging measurements of multiphase metal flows are challenging for two main reasons: the metals’ high melting temperatures and their opaqueness for visible light. This work focuses on X-ray and neutron radiographic experiments employing low-melting gallium alloys laden with model particles smaller than 1 mm in diameter. Both, bubbles and particles, are visualised simultaneously with high spatial and temporal resolution in order to analyse their motions by tracking algorithms. We demonstrate the capability of time-resolved X-ray and neutron radiography to image multiphase flows in particle-laden and optically opaque liquid metals, thus contributing to pave the way for systematic investigations on bubble–inclusion interactions in molten metals.

We demonstrate a new image processing methodology for resolving gas bubbles travelling through liquid metal from dynamic neutron radiography images with an intrinsically low signal-to-noise ratio. Image pre-processing, denoising and bubble segmentation are described in detail, with practical recommendations. Experimental validation is presented—stationary and moving reference bodies with neutron-transparent cavities are radiographed with imaging conditions representative of the cases with bubbles in liquid metal. The new methods are applied to our experimental data from previous and recent imaging campaigns, and the performance of the methods proposed in this paper is compared against our previously achieved results. Significant improvements are observed as well as the capacity to reliably extract physically meaningful information from measurements performed under highly adverse imaging conditions. The showcased image processing solution and separate elements thereof are readily extendable beyond the present application, and have been made open-source.

The electrosorption of Gd$^{3+}$ ions from aqueous 70 mM Gd(NO$_3$)$_3$ solution in monolithic carbon aerogel electrodes was recorded by dynamic neutron imaging. The aerogels have a bimodal pore size distribution consisting of macropores and mesopores centered at 115 nm and 15 nm, respectively. After the uptake of Gd$^{3+}$ ions by the negatively charged surface of the porous structure, an inhomogeneous magnetic field was applied to the system of discharging electrodes. This led to a convective flow and confinement of Gd(NO$_3$)$_3$ solution in the magnetic field gradient. Thus, a way to desalt and capture paramagnetic ions from an initially homogeneous solution is established.

Superabsorbent polymers (SAPs) are used to counteract self-desiccation in order to mitigate autogenous shrinkage, a problem in cementitious systems with a low water-to-cement ratio. The release kinetics during internal curing are of importance as not all SAP types are able to efficiently mitigate autogenous shrinkage. In this study, neutron tomography is used to study and visualize the water release kinetics over time. Per-voxel analysis of the time-attenuation curve was performed using piecewise-constant functions. Two different SAP types were studied, one being able to mitigate autogenous shrinkage and one quickly releasing its stored water after final setting. The tomography results correspond to autogenous shrinkage measurements and nuclear magnetic resonance tests. The visualization provides information on the time of water release by the SAPs after setting and the time window of internal curing. This opens additional insights towards the application of SAPs in the construction sector and provides information on the mechanism of internal curing.

The fast neutron imaging technique with recoil proton detection harbors significant potential for imaging of thick, large-scale objects containing high-Z elements. However, the challenge to find efficient fast neutron scintillators with high spatial resolution is ongoing. The list of requirements for such scintillators is long and demanding: a proton-rich, scattering-free material combining high light yield with the absence of light reabsorption. To meet these challenges, we look for a suitable material among a rising class of 0D organic-inorganic Pb(II) halide hybrids. The use of large organic cations, e.g., trihexyltetradecylphosphonium, results in room-temperature ionic liquids that combine highly Stokes-shifted (up to 1.7 eV), reabsorption-free, and efficient emission (photoluminescence quantum yield up to 60%) from molecularly small and dense (PbX2 molar fraction up to 0.33) emitting centers. We investigate the optical properties of the resulting ionic liquids and showcase their utility as fast neutron imaging scintillators. Concomitantly with good light yield, such fast-neutron scintillators exhibit both higher spatial resolution and lower γ-ray sensitivity compared with commercial ZnS:Cu-based screens., ACS Photonics, 8 (11), ISSN:2330-4022

Heat release from absorption storage heat pump by means of absorption of water vapor into aqueous sodium hydroxide is limited by uptake kinetics affecting temperature gain, as well as power- and energy density of the method. Earlier studies pinpoint that natural diffusion alone is not sufficient to reach higher uptake rate, and that the surface to bulk exchange has to be enforced. In this paper, different technical solutions to this problem for the heat storage application are introduced and studied by neutron imaging, enabling visual observation of water vapor uptake and diffusion. The experiments brought to the fore that the buoyancy changes associated with water uptake may be utilized to markedly enhance kinetics. This concept was applied on a vertically installed spiral finned tube operating as heat and mass exchanger for the absorption storage heat pump, also referred to as sorption heat storage. By flooding the space between the spiral fin with absorbent, water absorption into the vertical surface leads to a buoyancy driven movement of the liquid, supplying unspent aqueous NaOH to the vertical surface and exchanging it with the diluted liquid. This is found to increase the rate of absorption markedly. Under realistic heat storage specific operating conditions, a temperature gain of 12.5 K, an active area specific power of 1.28 kW/m(2) and an energy density of 243 kWh/m(3) in respect to the volume of charged absorbent (greatest volume) is reached. It is proposed that carful design of the spiral finned tube to enhance buoyancy movement will further improve overall sorption heat storage performance. (C) 2021 The Authors. Published by Elsevier Ltd., + ID der Publikation: hslu_91369 + Art des Beitrages: Wissenschaftliche Medien + Jahrgang: 182 + Sprache: Deutsch + Letzte Aktualisierung: 2022-12-16 10:42:56

Dynamic neutron radiography is used to observe the effect of a transverse magnetic field on argon bubbles rising through a thick layer of liquid gallium without interactions with the container walls.