Neutron Radiography Technique Research Articles

Wettability, imbibition and interdiffusion of lithium-based water-in-salt electrolytes in nanoporous carbon in relation to energy storage: A neutron radiography study

Superconcentrated lithium salt electrolytes, or lithium-based Water-in-Salt (WiS) electrolytes emerge as alternative electrolytes in supercapacitors and advanced batteries, such as the Li–O2 ones, especially when combined with a mesoporous carbon with very high surface area. In this work, we analyze the wettability, imbibition, and diffusivity of very concentrated lithium salts in a bimodal mesoporous carbon with pores of 5 nm and 25 nm in diameter. For the first time a neutron radiography technique is used to determine the imbibition and interdiffusion of lithium salts in mesoporous carbon. We found that a 20 m LiTFSI aqueous solution wets the surface of graphite and mesoporous carbon better than water. As a consequence, this WiS electrolyte is embedded rather fast in the mesoporous carbon by the action of capillary forces, exhibiting an intrinsic permeability K = (1.16 ± 0.03).10−18 m2. Finally, by resorting to the different cross-section of the 6Li and 7Li isotopes for the neutron capture, we could analyze the diffusion of LiCl in D2O confined in the mesoporous carbon. The interdiffusion coefficient of the confined LiCl is 5.0 10−7 cm2 s−1, corresponding to a tortuosity coefficient τ = 1.32. This moderate confinement effect results from the strong ion association of the LiCl that precludes the electrostatic interactions of Li+ ions with the negative charge on the pore walls. In summary, the combined properties of the lithium-based WiS electrolytes and the mesoporous carbon allow us to glimpse their use in supercapacitors and Li–O2 batteries.

Characteristics and neutron imaging of capillary water absorption for metakaolin and steel fiber reinforced slag based-geopolymer mortars

The manufacturing of cement consumes energy and natural resources of raw materials, and emits large amounts of CO2. Geopolymers are eco-friendly building materials that have the potential to replace cement-based building materials. We used neutron radiography to report new data on water absorption and distribution in metakaolin (MK) and steel fiber reinforced slag-based mortars for the first time. Due to contradictory studies on the influence of adding steel fibers to slag-based geopolymers on compressive strength and the limited research on water permeability, workability and sorptivity, new results were presented. Alkaline-activated MK and steel fiber reinforced slag -based geopolymer mortars were prepared. The neutron radiography (NR) technique was used to investigate capillary water absorption in the mortars. The fresh and mechanical strengths of the mortars, as well as their permeability, workability and sorptivity, were determined. The compressive, flexural, and splitting tensile strengths, as well as the water permeabilities, increased, whereas the workability decreased as the steel fiber percentage in slag-based mortars increased. The results showed that the addition of steel fiber at volume fractions of 1%, 2%, and 3% increased the −7 and 28 days compressive strengths for the slag-based mortars by 44.7%, 50.7%, and 57.1% and 41.9%, 50.2%, and 55.1%, respectively. The NR results revealed that the resistance to water penetration in reinforced slag-based mortars is greater than that of MK. The addition of steel fiber introduced inhomogeneity in the matrix of the reinforced samples and created water-accumulating regions. Water proceeded regularly in the Mk samples but irregularly in the slag-based mortars. The capillary absorption factors k for Mk and slag-based mortars with steel fiber at volume fractions of 1%, 2%, and 3% were found to be 0.37 cm min−1/2, 0.2 cm min−1/2, 0.17 cm.min−−1/2, 0.19 cm min−1/2, and 0.2 cm min−1/2, respectively. According to NR, the optimal percentage of steel fibers in the slag-based mortar impeding water flow is 1%–2%. Steel fiber used at a high proportion to slag-based mortars increased sorptivity. To best fit the results at high absorption times, the second Fick's law of diffusion can be used.

Tracer diffusion coefficients measurements on LaPO4-dispersed LATP by means of neutron radiography

Lithium tracer diffusion coefficients have been measured in Li1.3Al0.3Ti1.7(PO4)3 (LATP) and LATP – LaPO4 composite solid electrolytes in the temperature range between 300 °C and 500 °C by means of neutron radiography technique that utilizes the difference in neutron attenuation of 6Li and 7Li isotopes. The diffusion coefficient of LATP – LaPO4 composite is higher than that of pristine LATP, although the difference is much smaller than that estimated from the room temperature conductivity. This suggests that the bulk diffusion becomes the predominant diffusion mechanism at 300 °C to 500 °C instead of the diffusion along the space charge layer formed around the LaPO4 dispersants.

Synthesis and characterization of borate glasses for thermal neutron scintillation and imaging

With the aim of finding promising neutron scintillators, different compositions have been synthesized in the glassy phase and subsequently characterized for their performance as the scintillation screen of thermal neutron imaging systems. Three new compositions having Li, B, and Gd as principal constituents, doped with Eu have been synthesized by the melt quenching method and investigated the first time for neutron imaging in the present study. The concentration of luminescent activator, Eu3+ has been optimized by performing X-ray induced emission of these glass samples. Beam purity investigation along with the luminescence ability of the commercial screen have been also performed prior to the thorough evaluation of the thermal neutron scintillation characteristics of the compositions. The glass samples have been exposed to thermal neutrons for 5 and 10 min separately at the beam port of the research reactor for their performances in conventional direct film neutron radiography technique. The glasses containing Gd have been found to have higher light yield due to energy transfer from Gd ions to Eu activators. However, the composition of 60Li2O3:10Y2O3:28.5B2O3:1.5Eu2O3 (mol%) has been observed to have low light but good thermal neutron discrimination property from the gamma background despite having lesser X-ray luminescence among all three.

Characterization of wood-borax composites as alternative neutron shielding material using neutron radiography techniques

To protect operators of equipment using neutron radiation, an alternative material is needed as a neutron shielding which is lightweight and has a high neutron absorption. One alternative material that can be used is wood dust. In this study pure wood sawdust and 30% borax-wood composites were investigated as alternatives to shielding neutrons. Mixing wood sawdust and borax was done using HEM (High Energy Milling) for 1 hour, then pressed at 2000 Psi using a manual press with variations in thickness of 5 mm, 10 mm, 15 mm and 20 mm. SEM characterization results show, the grain size of wood in pure wood and 30% boraxwood composites is still quite large around 50 μm, the EDS results show no significant difference in wood content and 30% borax-wood composites. XRD characterization results showed no new phases were formed in the 30% borax-wood composite. The results of observations with optical microscopy showed that 30% borax-wood composite which were compressed did not form pores but were not evenly distributed. From the compressive test data, there was a decrease in the compressive ability of 30% borax-wood composites compared to pure wood dust from 226.6 N to 110.4 N. The neutron absorption test results using the Neutron Radiography technique with the film technique showed the addition of 30% borax to sawdust increased the neutron absorption rate by an average of 19.05% in wood to 20.24% in 30% borax-wood composites and increased the attenuation coefficient of 0.36 cm· in pure wood to 0.53 cm 1 in 30% borax-wood composite.

Energy-selective neutron imaging by exploiting wavelength gradients of double crystal monochromators—Simulations and experiments

Abstract The potential of wavelength resolved neutron transmission experiments is well known. This paper is focused on the performance of the double crystal monochromator which is widely used at steady state neutron sources and compares simulation results based on neutron ray tracing with experimental results in order to provide a better understanding of the device. The influences of crystal mosacities on the neutron beam is reported for the utilised setup and the resulting wavelength gradients along one direction are determined. For the neutron imaging geometry applied, a wavelength gradient of about 0.005 A/cm at the sample position was found. Moreover, a new neutron radiography technique for Bragg edge mapping in imaging experiments utilising a neutron wavelength gradient at the sample position was developed and is reported. Experiments and simulations are found to be in good agreement.

Impact of Porosity Gradients within Catalyst Layer and MPL of a PEM Fuel Cell on the Water Management and Performance: A Neutron Radiography Investigation

The influence of porosity modification of both the cathode microporous layer (MPL) and catalyst layer (CL) of a low temperature polymer electrolyte membrane fuel cell (PEMFC) is studied with a neutron radiography technique to determine the water distribution and transport inside the cell. Three types of cathode MPLs with varying porosity distributions are made by introducing Chemisnow® monodisperse spherical polymer particles with 1.5 μm and 30 μm diameters inside the MPL slurry. CLs with three different porosities are manufactured by incorporation of 0 to 10 wt.% polystyrene particles with 0.5 μm diameters. Water thicknesses are measured inside the cell components at relative humidity of 120% with an increasing current density up to 1 A/cm². The results indicate that introducing micro pores into the structure of the MPL and CL may lead to the extraction of the excess water through these pores, leaving smaller pores accessible for the reaction gases and better cell performance.

Estimation of volumetric water content during imbibition in porous building material using real time neutron radiography and artificial neural network

Abstract Movement of fluids through porous media is of great significance in different sciences such as civil engineering and chemical technology. When a fluid is introduced to a porous media, the fluid starts moving and diffusing through that. In this condition, the amount of fluid in each position of the porous material is a function of the distance between the desired position and the fluid movement starting point as well as the elapsed time. In this research, a novel methodology is proposed for estimating the volumetric water content in different times and positions during the water imbibition inside the porous building materials using a combination of real time neutron radiography technique and artificial neural network (ANN). For this purpose, a brick as a porous construction sample was positioned in contact with a water container and 145 neutron radiographs were recorded during the water imbibition inside the brick. To extract the required data for training, testing and validating the ANN, a line of pixels in the center of brick’s image along with the water movement direction inside the sample was considered. The calculated volumetric water content in each position of the mentioned line was used as the output of the ANN. In addition, the elapsed time and position were utilized as the two inputs of the ANN. After training, the proposed ANN model could estimate the volumetric water content in different times and positions in direction of water movement inside the brick with a mean square error (MSE) of less than 8.4 × 10−4.

Measurement of the thickness of B4C layers deposited over metallic grids via multi-angle neutron radiography

At the present time, different kinds of thermal neutron detectors are under development at the European Spallation Source research facility, in order to overcome the well-known problem of the 3He shortage. One of these new systems relies on the use of a 3D neutron converter cathode that consists of a stack of aluminum grids, covered by a 0.9 µm 10B enriched boron carbide layer (10B4C). As the conversion efficiency is a function of the boron thickness and the mean free path of the charged particles produced in the neutron induced reaction, the characterization of the boron carbide layer uniformity over the grids becomes crucial. In this work, a non-destructive method to map the thickness distribution of the converter layer over the grids is shown. The measurements exploit the white-beam neutron radiography technique where the specimen is irradiated at different angles. This experiment has been performed at the IMAT beamline operating at the ISIS spallation neutron source (UK). The results confirm that this non-destructive, wide-ranging technique allows a reliable and fast sample characterization and that it may be exploited in similar analyses where equivalent requirements are requested.

Rhizosphere hydrophobicity limits root water uptake after drying and subsequent rewetting

Recent experiments showed that rhizosphere of several plant species turns temporarily hydrophobic after severe drying and subsequent rewetting. Whether or not such hydrophobicity limits root water uptake is not known. A set of experiments was performed to test whether rhizosphere water repellency negatively affects root water uptake. To this end, a commercial surfactant was used as a rewetting agent to facilitate the wettability of the rhizosphere of lupins (Lupinus albus) in a sandy soil. Lupin plants were grown in rhizoboxes and were subjected to a severe drying cycle. Then half of the plants were irrigated with water and half with the surfactant solution. Time-series neutron radiography technique was used to monitor water redistribution in the rhizosphere during irrigation. In a second experimental set-up, lupins were grown in a sandy soil partitioned in five vertical compartments separated by a 1-cm layer of coarse sand (acting as a capillary barrier). Water and surfactant were injected in different compartments and the rehydration of the root tissues beyond the irrigated compartments was monitored with neutron radiography for 2–3 h. Root rehydration rates were used to estimate the water fluxes across the root-soil interface. The rhizosphere of lupin roots in sandy soil irrigated with water remained partly dry for at least 2–3 h, while it was rapidly rewetted when irrigated with surfactant. Water flow into the roots irrigated with surfactant solution was 6.5 times faster than into the roots irrigated with water. These results prove that water repellency of the rhizosphere of lupins in sandy soils limited the water fluxes into the roots and root rehydration during the first two to three hours after irrigation. This might not always be negative, because it can limit water losses from roots to dry soil and therefore avoid severe root dehydration.

Applying neutron transmission physics and 3D statistical full-field model to understand 2D Bragg-edge imaging

Bragg-edge imaging, which is also known as neutron radiography, has recently emerged as a novel crystalline characterization technique. Modelling of this novel technique by incorporating various features of the underlying microstructure (including the crystallographic texture, the morphological texture, and the grain size) of the material remains a subject of considerable research and development. In this paper, Inconel 718 samples made by additive manufacturing were investigated by neutron diffraction and neutron radiography techniques. The specimen features strong morphological and crystallographic textures and a highly heterogeneous microstructure. A 3D statistical full-field model is introduced by taking details of the microstructure into account to understand the experimental neutron radiography results. The Bragg-edge imaging and the total cross section were calculated based on the neutron transmission physics. A good match was obtained between the model predictions and experimental results at different incident beam angles with respect to the sample build direction. The current theoretical approach has the ability to incorporate 3D spatially resolved microstructural heterogeneity information and shows promise in understanding the 2D neutron radiography of bulk samples. With further development to incorporate the heterogeneity in lattice strain in the model, it can be used as a powerful tool in the future to better understand the neutron radiography data.

Applications of Neutron Radiography for the Nuclear Power Industry

The World Conference on Neutron Radiography (WCNR) and International Topical Meeting on Neutron Radiography (ITMNR) series have been running over 35 years. The most recent event, ITMNR-8, focused on industrial applications and was the first time this series was hosted in China. In China, more than twenty new nuclear power plants are under construction and plans have been announced to increase the nuclear capacity by a factor of three within fifteen years. There are additional prospects in many other nations. Neutron tests were vital during previous developments of materials and components for nuclear power applications, as reported in the WCNR and ITMNR conference series. For example a majority of the 140 papers in the Proceedings of the First WCNR are for the benefit of the nuclear power industry. Many of those techniques are being utilized and advanced to the present time. Neutron radiography of irradiated nuclear fuel provides more comprehensive information about the internal condition of irradiated nuclear fuel than any other non-destructive technique to date. Applications include examination of nuclear waste, nuclear fuels, cladding, control elements, and other critical components. In this paper, applications of neutron radiography techniques developed and applied internationally for the nuclear power industry since the earliest years are reviewed, and the question is asked whether neutron test techniques, in general, can be of value in development of the present and future generations of nuclear power plants world-wide.

Experimental investigation of the thermal hydraulics of supercritical water under natural circulation in a closed loop

The thermal hydraulics of supercritical water under forced-, mixed convection and natural circulation conditions is not fully understood. In order to study the thermal hydraulic behaviour of this fluid under natural circulation conditions a small size, closed experimental loop has been designed and built. The thermal hydraulic phenomenon occurring in the loop can be measured by thermocouples mounted onto the outer surface of the heated tube wall, absolute and differential pressure transducers and a flow meter; moreover, simultaneously can be visualized by neutron radiography techniques. This paper describes the loop itself, the process of the experiment with the measurement techniques, the data acquisition system applied and the results got during the first measurement series. Based on the results of the first measurement series, it was found that the measured part of the steady state characteristic is independent from the system pressure. A slight dependence of steady state characteristic on the inlet temperature can be identified: the higher the inlet temperature the higher the mass flow rate. The total pressure drop and its components seem to be independent from the system pressure but strongly dependent on the inlet temperature due to the influence of bulk-fluid temperature on the relevant thermophysical properties (density and dynamic viscosity). The pressure drop due to acceleration of flow found to be negligible next to the two dominant components, the pressure drop due to frictional resistance and due to gravity. The coupled evaluation of the radiographic images and the thermophysical properties of water have shown that the main driving force behind the decrease of the neutron attenuation is the decreasing water density as the bulk-fluid temperature increases. The reverse of this relationship could be exploited during the validation of future Monte Carlo simulations.

Estimation of the hydraulic conductivities of lupine roots by inverse modelling of high-resolution measurements of root water uptake.

Background and Aims Radial and axial hydraulic conductivities are key parameters for proper understanding and modelling of root water uptake. Despite their importance, there is limited experimental information on how the radial and axial hydraulic conductivities vary along roots growing in soil. Here, a new approach was introduced to estimate inversely the profile of hydraulic conductivities along the roots of transpiring plants growing in soil. Methods A three-dimensional model of root water uptake was used to reproduce the measured profile of root water uptake along roots of lupine plant grown in soil. The profile of fluxes was measured using a neutron radiography technique combined with injection of deuterated water as tracer. The aim was to estimate inversely the profiles of the radial and axial hydraulic conductivities along the roots. Key Results The profile of hydraulic conductivities along the taproot and the lateral roots of lupines was calculated using three flexible scenarios. For all scenarios, it was found that the radial hydraulic conductivity increases towards the root tips, while the axial conductivity decreases. Additionally, it was found that in soil with uniform water content: (1) lateral roots were the main location of root water uptake; (2) water uptake by laterals decreased towards the root tips due to the dissipation of water potential along the root; and (3) water uptake by the taproot was higher in the distal segments and was negligible in the proximal parts, which had a low radial conductivity. Conclusions The proposed approach allows the estimation of the root hydraulic properties of plants growing in soil. This information can be used in an advanced model of water uptake to predict the water uptake of different root types or different root architectures under varying soil conditions.

Quality Study of Rice Husk Ash (RHA) Brick Using Neutron Radiography Technique

A powerful non-destructive testing (NDT) technique is adopted to study the quality of RHA brick-1 and RHA brick-2. In that case, rice husk ash has been utilized for the preparation of bricks in full replacement of clay. In these studies, homogeneity of elemental distribution, water absorption and size and shape of the pores have been observed. From the studies, it was observed that ele- mental distribution is very good at various level, large number of porosity is presented with little bit size, initial rate of absorption (IRA) due to first five minutes immersion of water is higher compared to other immersion time (>5 minute), incremental water intrusion area increases very slowly with the increasing immersion time and the water absorption for RHA brick-2 becomes sa- turated very early than that of the RHA brick-1.

Diffusion Mechanism and Quantitative Measurement of Moisture Transport in Porous Silica Gel Filter Using Dynamic Neutron Radiography Technique

Neutron radiography (NR) can investigate the diffusion mechanisms of moisture transport within the silica gel material. Dynamic neutron radiography (DNR) possesses the possibility to investigate the moisture profile inside the silica gel filter. The technique explained the relationship between moisture movement and time. This study investigated the diffusion mechanisms (absorption and infiltration) of moisture in the silica gel filter by state-of-the-art dynamic neutron radiography (DNR) technique and advanced software. This study also measured the ability of the DNR technique to find out the diffusion coefficients of a silica gel filter material as a function of temperature and time.

Neutron Radiography of Irradiated Nuclear Fuel at Idaho National Laboratory

Neutron radiography of irradiated nuclear fuel provides more comprehensive information about the internal condition of irradiated nuclear fuel than any other non-destructive technique to date. Idaho National Laboratory (INL) has multiple nuclear fuels research and development programs that routinely evaluate irradiated fuels using neutron radiography. The Neutron Radiography reactor (NRAD) sits beneath a shielded hot cell facility where neutron radiography and other evaluation techniques are performed on these highly radioactive objects. The NRAD currently uses the foil-film transfer technique for imaging fuel that is time consuming but provides high spatial resolution. This paper describes the NRAD and hot cell facilities, the current neutron radiography capabilities available at INL, planned upgrades to the neutron imaging systems, and new facilities being brought online at INL related to neutron imaging.

Visualization of Hydrazine Decomposition in a Catalyst Bed by Using Neutron Radiography

Most mono-propellant thruster technologies were developed in the 1960s. Those basic principles and fundamental mechanisms, such as the catalyst and propellant, are still in use without major technical innovation. However, much remains to be clarified in terms of the mechanisms and quantitative limitations of the hydrazine decomposition phenomena inside the mono-propellant thruster. Therefore, in order to enhance the reliability of the propulsion systems, it should be promising to perform the direct observation of the physical and chemical phenomena occurring in the catalyst bed of the mono-propellant thruster. For that purpose, a visualization of the mono-propellant thruster was performed by using high frame-rate neutron radiography technique. The experiments were conducted at the Kyoto University Research Reactor and the hydrazine injection behavior to the catalyst bed was visualized clearly.

Internal defects and water absorption behavior of environmentally friendly brick-MAB using film neutron radiography technique

Film neutron radiography (NR) technique has been adopted to study the internal defects likehomogeneity, porosity, incremental intrusion area, initial rapid absorption (IRA) and water penetratingheight/behavior of the automated machine made environmentally friendly brick-MAB sample.Thermal neutron radiography facility installed at the tangential beam port of 3 MW TRIGA MARK-IIreactor was used in this study. In here optical density or gray values of the neutron radiographicimages of the sample was measured. From the measurement it was found that most of the areas of thissample were homogeneous, which indicateed the presence of a little bit internal porosity andabsorption of water to be very poor. It also showed that its initial rapid absorption was less and waterabsorption behavior was capillary and of wave shape. DOI: http://dx.doi.org/10.3329/jbas.v38i1.20197 Journal of Bangladesh Academy of Sciences, Vol. 38, No. 1, 1-6, 2014

Improved track-etch neutron radiography using CR-39

Currently most state-of-the-art setups for neutron radiography use scintillator screens and CCD cameras for imaging. However, in some situations it is not possible to use a CCD and alternatives must be considered. One such alternative is the well-established technique of track-etch neutron radiography, which has as main disadvantages requiring a long time for image recording and generating images with a relatively low contrast. In this work we address these negative issues and report significant improvements to recording and digitizing images using an improved setup consisting of an enriched 10B converter, a CR-39 solid state nuclear track detector and a flatbed scanner. The improved setup enables a significant reduction of the fluence required to obtain a neutron radiography image using this technique. Comparisons are made with imaging using two CCD models in the same beam line, so that the results can be extrapolated for other facilities.