Application Of Neutron Radiography Research Articles

Fast neutron radiography detector with polyethylene converter and MCP: development and performance evaluation

We present a new position-sensitive fast neutron detector for 14 MeV fast neutron radiography, comprising a high-density polyethylene converter, a micro-channel plate (MCP), a P43 phosphor screen, a reflection mirror, and a CCD camera. Experimental tests are conducted using a DT neutron generator at CIAE, with different samples and a knife-edge measurement used to determine overall image resolution. Results show that the detector is feasible for fast neutron radiography, producing a fast neutron image with a neutron flux of ∼ 3.22 × 104 n · s-1 · cm-2 and 120 s exposure time. Our study demonstrates the potential of this detector for use in fast neutron radiography applications.

Ageing management of research reactors instrumentation using neutron radiography applications

This paper introduces the applications of neutron radiography and tomography to improve maintenance and aging management programs in research reactors. Egypt second research reactor (ETRR-2) has an advanced neutron radiography/tomography facility and it is used to shoot and test different objects such as concerning antiquities, industry and applied research in various fields. Neutron radiography/tomography (NR/T) techniques offer ideal opportunities for nondestructive testing (NDT) evaluations. It has been possible to benefit from the applications and use of radiography to help improve maintenance of components and systems as well as aging management programs for the ETRR-2. This work proposes successful applications of NR/T to inspect and test different safety and safety related components such solenoid valves and the shielding tube of the defective fuel instrument to predict both damage and edging of these systems. Also, the NR technique monitored successfully the behavior efficiency of an air filtering unit (AFU) for dust removal from ventilation system in the research reactors. Additionally, we measured the capability of protective maintenance procedures to remove impurities or blockage from a stainless steel filter (SSF) used in water treatment system. NR/T techniques are successfully applied and enhanced both maintenance and ageing management programs of ETRR-2 instrumentation, equipment and systems.

Neutronic feasibility study of using a multipurpose MNSR for BNCT, NR, and NAA

In this study, the conceptual design of a multipurpose research reactor for boron neutron capture therapy (BNCT), neutron radiography (NR) and neutron activation analysis (NAA) applications has been performed. Specifically, a suitable epithermal neutron flux (φEpi) of about 1×109 (n.cm−2.s−1) for BNCT and high quality thermal neutron flux (φTh) of above 1×106 (n.cm−2.s−1)for NR are carried out based on our LEU reactor core designing. The UO2 fuel with density of 10.5 g/cm3 and enrichment of 12.4% is applied as an appropriate LEU fuel. The reactor safety is assured by designing the safety control rod system with two banks. A fission converter facility (FCF) consists of 19 fuel rods of UO2 is used to increase φEpi for BNCT treatment. Furthermore, a unique thermal column of heavy water is used to increase φTh for NR purpose. Four internal irradiation sites, two external irradiation sites, and one large thermal column irradiation site are considered at the reactor which can be used for NAA application. The results of neutronic calculations show that the reactor meets the neutronic design limits for a low power research reactor.

Hydrogenous content identification in heterogeneous cargoes via multiple monoenergetic neutron radiography

The determination of hydrogenous content in commercial cargoes is an important challenge in cargo security. Prior work has shown the feasibility of hydrogenous cargo classification in radiographic applications. This result was achieved by using the significant material to material differences in the energy dependence of their neutron scattering cross-sections. The work presented here details the application of this technique to multiple-monoenergetic neutron transmission measurements of several heterogeneous cargo mock-ups with the goal of quantifying hydrogenous content. It demonstrates the ability to determine the hydrogenous content of a cargo container by performing analysis of pulse-height data of transmitted neutrons. The set-up used for these feasibility studies was able to detect and quantify areal densities of up to 30 g/cm$^2$ of high density polyethylene (HDPE), even when mixed with metallic materials. Accurate determination of the hydrogenous content of the cargo has two important uses: it can allow for better imaging and discrimination of conventional contraband during cargo screening; it may also allow the unfolding of the individual elemental contributions from an effective atomic number, $Z_{\mathrm{eff}}$, as determined from multiple monoenergetic gamma radiography (MMGR). This combination of capabilities could make multiple monoenergetic neutron radiography applications a significant contribution to cargo security.

Focusing mirrors for enhanced neutron radiography with thermal neutrons and application for irradiated nuclear fuel

Neutron radiography is a powerful method of probing the structure of materials based on attenuation of neutrons. This method is most suitable for materials containing heavy metals, which are not transparent to X-rays, for example irradiated nuclear fuel and other nuclear materials. Neutron radiography is one of the first non-distractive post-irradiated examination methods, which is applied to gain an overview of the integrity of irradiated nuclear fuel and other nuclear materials. However, very powerful gamma radiation emitted by the samples is damaging to the electronics of digital imaging detectors and has so far precluded the use of modern detectors. Here we describe a design of a neutron microscope based on focusing mirrors suitable for thermal neutrons. As in optical microscopes, the sample is separated from the detector, decreasing the effect of gamma radiation. In addition, the application of mirrors would result in a thirty-fold gain in flux and a resolution of better than 40 μm for a field-of-view of about 2.5 cm. Such a thermal neutron microscope can be useful for other applications of neutron radiography, where thermal neutrons are advantageous.

Application of neutron radiography for in-situ visualization of gallium solidification in travelling magnetic field

Application of neutron radiography for in-situ visualization of gallium solidification in travelling magnetic field

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.

Application of neutron radiography in observing and quantifying the time-dependent moisture distributions in multi-cracked cement-based composites

Significant tensile strain capacity of SHCC under tensile stress can be reached by multi-crack formation, while the cracks remain bridged by fibres. Ductility of SHCC is due to this multi-crack formation. Cracks are preferential pathways for ingress of water and salt solutions into the material. In this contribution neutron radiography has been successfully applied to visualize the process of water penetration into cracked SHCC and to quantify the corresponding time-dependent moisture distributions in cracked SHCC. Results indicate that in uncracked SHCC, less water can be found. Once cracked, however, both the amount of water and the penetration depth increased with increasing of crack density and the wider crack pattern when higher tensile strain was applied. Even at comparatively modest imposed strain when micro-cracks were formed, water penetrated into the specimens along the cracks of 30 μm–50 μm immediately and then water migrated further into the surrounding matrix from water filled cracks. Water then moved into the matrix adjacent to the cracks which was mechanically damaged by direct tension. Therefore, if durability of SHCC is an issue for application, a maximum strain may not be exceeded. In order to prevent penetration of water or salt solutions into cracked SHCC, two approaches were used. Integral water repellent SHCC was prepared by adding silane emulsion to the fresh mortar. Compared with neat SHCC, the integral water repellent SHCC with multi-cracks absorbed much less water after imposed to the same tensile strain. Notice that there was still a small amount of moisture that could enter the matrix of integral water repellent SHCC via cracks when the tensile strain was over 1.5% in this study. As an alternative method, surface impregnation with silane gel was a more promising approach to protect cracked SHCC from water or salt solution penetration into the material when multi-cracks formed.

Design, construction and characterization of a new neutron beam for neutron radiography at the Tehran Research Reactor

To obtain a thermal neutron beam for neutron radiography applications, a neutron collimator has been designed and implemented at the Tehran Research Reactor (TRR). TRR is a 5MW open pool light water moderated reactor with seven beam tubes. The neutron collimator is implemented in the E beam tube of the TRR. The design of the neutron collimator was performed using MCNPX Monte Carlo code. In this work, polycrystalline bismuth and graphite have been used as a gamma filter and an illuminator, respectively. The L/D parameter of the facility was chosen in the range of 150–250. The thermal neutron flux at the image plane can be varied from 2.26×106 to 6.5×106ncm−2s−1. Characterization of the beam was performed by ASTM standard IQI and foil activation technique to determine the quality of neutron beam. The results show that the obtained neutron beam has a good quality for neutron radiography applications.

Deterministic simulation of thermal neutron radiography and tomography

Abstract In recent years, thermal neutron radiography and tomography have gained much attention as one of the nondestructive testing methods. However, the application of thermal neutron radiography and tomography is hindered by their technical complexity, radiation shielding, and time-consuming data collection processes. Monte Carlo simulations have been developed in the past to improve the neutron imaging facility’s ability. In this paper, a new deterministic simulation approach has been proposed and demonstrated to simulate neutron radiographs numerically using a ray tracing algorithm. This approach has made the simulation of neutron radiographs much faster than by previously used stochastic methods (i.e., Monte Carlo methods). The major problem with neutron radiography and tomography simulation is finding a suitable scatter model. In this paper, an analytic scatter model has been proposed that is validated by a Monte Carlo simulation.

Digital neutron image enhancement based on total variation-based ℓ0 minimization

For the digital neutron radiography applications, low contrast is inevitable due to the neutron and photon statistics limited or high transmission (and low attenuation) in the sample. In this paper, we introduce a total variation-based ℓ0 minimization model and solve it by an alternating minimization approach. The proposed model is applied to base & detail decomposition for the dynamic range modification and detail magnification. Experimental results on several real neutron images are presented to demonstrate the effectiveness of the proposed method.

Semiconductor Thermal Neutron Detector

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Trouble Shooting of Deuteron RFQ for PKUNIFTY

A 201.5MHz deuteron four-rod RFQ was designed and operated to generate high flux neutron for the application of neutron radiography at Peking University, which is called as Peking University Neutron Imaging Facility (PKUNIFTY). This paper presents two kinds of tuners to tune the cavity to the designed frequency and reach the needed field unflatness distribution less than 5%; the RFQ intervane voltage 70.7kV determination by the roentgen spectrum measurement at 237.6kW; output accelerated deuteron beam energy at 2.0 MeV with energy spread of 2.5% at 300kW including additional about 60kW beam power. Although it has been running more than one year, sometimes we have troubles not only for the RFQ, mainly for the RF system. This paper showed some troubles and its shootings methods. Some troubles and shooting methods might be useful for similar projects.

Neutron Radiography Applications in Studies of Drying of Capillary-Porous Systems

The application of modern digital neutron radiography in the study of the drying process in porous media is demonstrated with two simple examples of cylindrical and rectangular samples made of different materials. The statistical method of image analysis is presented and the standard deviation of grey scale values (referred to brightness) is shown to be a useful measure of receding drying front emergence. The motion of the drying front was analyzed and found neither linear nor proportional to the square root of time and was delineated with nonlinear functions different for each sample shape.

Spatial resolution of a [formula omitted] neutron imaging detector

We present a detailed study of the spatial resolution of our time-resolved neutron imaging detector utilizing a new neutron position reconstruction method that improves both spatial resolution and event reconstruction efficiency. Our prototype detector system, employing a micro-pattern gaseous detector known as the micro-pixel chamber (μPIC) coupled with a field-programmable-gate-array-based data acquisition system, combines 100μm-level spatial and sub-μs time resolutions with excellent gamma rejection and high data rates, making it well suited for applications in neutron radiography at high-intensity, pulsed neutron sources. From data taken at the Materials and Life Science Experimental Facility within the Japan Proton Accelerator Research Complex (J-PARC), the spatial resolution was found to be approximately Gaussian with a sigma of 103.48±0.77μm (after correcting for beam divergence). This is a significant improvement over that achievable with our previous reconstruction method (334±13μm), and compares well with conventional neutron imaging detectors and with other high-rate detectors currently under development. Further, a detector simulation indicates that a spatial resolution of less than 60μm may be possible with optimization of the gas characteristics and μPIC structure. We also present an example of imaging combined with neutron resonance absorption spectroscopy.

Development of a Time-resolved Neutron Imaging Detector Based on the μPIC Micro-Pixel Chamber

We have developed a prototype time-resolved neutron imaging detector employing a micro-pattern gaseous detector known as the micro-pixel chamber ({\mu}PIC) coupled with a field-programmable-gate-array-based data acquisition system. Our detector system combines 100{\mu}m-level spatial and sub-{\mu}s time resolutions with a low gamma sensitivity of less than 10^-12 and high data rates, making it well suited for applications in neutron radiography at high-intensity, pulsed neutron sources. In the present paper, we introduce the detector system and present several test measurements performed at NOBORU (BL10), J-PARC to demonstrate the capabilities of our prototype. We also discuss future improvements to the spatial resolution and rate performance.

Application of Neutron Radiography to Flow Visualization in Supercritical Water

Abstract Supercritical water is used in various chemical reaction processes including hydrothermal synthesis of metal oxide nano-particles, oxidation, chemical conversion of biomass and plastics. Density of the super critical water is much less than that of the sub-critical water. By using neutron radiography, Peterson et al. have studied salt precipitation processes in supercritical water and the flow pattern in a reverse-flow vessel for salt precipitation, and Balasko et al. have revealed the behaviour of supercritical water in a container. The nano-particles were made by mixing the super critical flow and the sub critical water solution. In the present study, neutron radiography was applied to the flow visualization of the super and sub critical water mixture in a T-junction made of stainless steel pipes for high pressure and temperature conditions to investigate their mixing process. Still images by a CCD camera were obtained by using the neutron radiography system at B4 port in KUR.

Novel Application of Neutron Radiography to Forced Convective Drying of Fruit Tissue

Neutron imaging is a promising technique to study drying processes in food engineering as it is a non-intrusive, non-destructive technique, which provides quasi-real-time quantitative information of the water loss during drying and of the internal water distribution, at a high spatial and dynamic resolution. Particularly, the high sensitivity to water is its main advantage for drying studies, despite the limited accessibility to reactor facilities, which produce neutrons. This technique was used to investigate forced convective drying of fruit tissue (pear and apple), placed in a small wind tunnel. Water loss, water distribution in the sample and sample shrinkage were evaluated as a function of time. The water loss, determined quantitatively from neutron radiographs, was underestimated slightly compared to gravimetrical measurements. The overall drying behaviour agreed well with control measurements performed in a climatic chamber and was very similar for both fruit tissues. The corresponding shrinkage behaviour of both tissues was also similar. The large shrinkage, which is characteristic for soft biological materials such as food products, however, hindered post-processing to some extent. From the internal water distribution, the water gradients within the sample, induced by drying, were visualised and were found to predominantly occur at the air–material interface, indicating that the water transport inside the tissue dominated the water loss, instead of the convective exchange with the air flow. Neutron imaging was shown to exhibit unique benefits for studying drying processes of food.

High resolution neutron counting detectors with microchannel plates and their applications in neutron radiography, diffraction and resonance absorption imaging

The event counting detection technology based on signal amplification in microchannel plates (MCPs) was initially developed for the applications with relatively low fluxes of photons, electrons and...

Neutron imaging detector based on the [formula omitted] micro-pixel chamber

We have developed a prototype time-resolved neutron imaging detector employing the micro-pixel chamber (μPIC), a micro-pattern gaseous detector, coupled with a field programmable gate array-based data acquisition system for applications in neutron radiography at high-intensity neutron sources. The prototype system, with an active area of 10×10cm2 and operated at a gas pressure of 2atm, measures both the energy deposition (via time-over-threshold) and three-dimensional track of each neutron-induced event, allowing the reconstruction of the neutron interaction point with improved accuracy. Using a simple position reconstruction algorithm, a spatial resolution of 349±36μm was achieved, with further improvement expected. The detailed tracking allows strong rejection of background gamma-rays, resulting in an effective gamma sensitivity of 10−12 or less, coupled with stable, robust neutron identification. The detector also features a time resolution of 0.6μs.