Neutron Imaging Plate Research Articles

Application of neutron imaging plate and neutron CT methods on nuclear fuels and materials

Advanced neutron radiography techniques such as the neutron imaging plate (NIP) and neutron computed tomography (NCT) methods have been investigated in the practicability for the postirradiation examination (PIE). In current works, an unirradiated fuel rod was examined by NIP and NCT methods in order to collect the fundamental data for applying these techniques to the PIE. A fuel rod used is composed of seven-enriched UO/sub 2/ and two-natural UO/sub 2/ pellets with controlled sizes and shape that are loaded into a Zircaloy tube. The neutron radiography tests were performed by NIP and NCT methods at the 2nd Thermal Neutron Radiography Facility (TNRF-2) in the Japan Research Reactor (JRR)-3. In the NIP image of the fuel rod, the difference in the size, shape, and enrichment between the UO/sub 2/ pellets is obviously recognized. In the case of NCT method, the images clearly show the detailed shape of the cross section in both enriched and natural pellets; and difference in the enrichment between those pellets is also observed. In addition, size difference between fuel parts of specifications and those in NCT images is evaluated.

Current Status of Neutron Imaging Plate

Current status of neutron imaging plate (NIP) is reviewed. The characteristics of NIP is given by comparing with the one of the gas-fnled proportional position sensitive detector (PSD). The gamma-ray sensitivity and optimum condition of the NIP are reviewed. The future prospect of the NIP is presented.

Optimization of a neutron image plate detector with low γ-sensitivity

Recent experimental studies on new materials (storage phosphors and neutron converter) to be used in a low γ -sensitive neutron image plate detector have been performed at the Research Center Jülich and Darmstadt University of Technology. It was shown that a mixture LiF+KCl:Eu 2+ (or KBr:Eu 2+) features a higher neutron/gamma signal ratio compared to BaFBr:Eu 2+mixed with Gd as in commercially available neutron image plates. However, the smaller neutron capture cross-section of 6Li in comparison with Gd requires the use of significantly thicker recording layers. This article presents the results of numerical estimations for the performance of such a detector. The use of image plates with a thick recording layer and a regular cell structure allowing for the increase in spatial resolution (pixelated image plate) is discussed.

Neutron crystal structure analysis of polyethylene‐d4: The application of a neutron imaging plate

AbstractNeutron diffraction provides a more detailed structure than X‐ray diffraction. In this study, a neutron crystal structure analysis of polyethylene‐d4 was carried out with a neutron imaging plate. This was the first crystal analysis of the crystalline polymer with the neutron fiber pattern. The procedure was almost the same as that in a previous work, in which the neutron structure analysis was carried out on the basis of the equatorial reflections. The azimuthal angle of the molecule with respect to the a axis was estimated to be 46.3°. This corresponded well to the value of 45° estimated in the previous work within the accuracy of the standard deviations. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3836–3839, 2004

Pixelated neutron image plates

Neutron image plates (NIPs) have found widespread application as neutron detectors for single-crystal and powder diffraction, small-angle scattering and tomography. After neutron exposure, the image plate can be read out by scanning with a laser. Commercially available NIPs consist of a powder mixture of BaFBr : Eu2+ and Gd2O3 dispersed in a polymer matrix and supported by a flexible polymer sheet. Since BaFBr : Eu2+ is an excellent x-ray storage phosphor, these NIPs are particularly sensitive to γ-radiation, which is always present as a background radiation in neutron experiments. In this work we present results on NIPs consisting of KCl : Eu2+ and LiF that were fabricated into ceramic image plates in which the alkali halides act as a self-supporting matrix without the necessity for using a polymeric binder. An advantage of this type of NIP is the significantly reduced γ-sensitivity. However, the much lower neutron absorption cross section of LiF compared with Gd2O3 demands a thicker image plate for obtaining comparable neutron absorption. The greater thickness of the NIP inevitably leads to a loss in spatial resolution of the image plate. However, this reduction in resolution can be restricted by a novel image plate concept in which a ceramic structure with square cells (referred to as a ‘honeycomb’) is embedded in the NIP, resulting in a pixelated image plate. In such a NIP the read-out light is confined to the particular illuminated pixel, decoupling the spatial resolution from the optical properties of the image plate material and morphology. In this work, a comparison of experimentally determined and simulated spatial resolutions of pixelated and unstructured image plates for a fixed read-out laser intensity is presented, as well as simulations of the properties of these NIPs at higher laser powers.

Neutron protein crystallography in JAERI

Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins. After developing an original neutron detector (neutron imaging plate) and a novel practical neutron monochromator (elastically bent perfect Si monochromator), BIX-type diffractometers which were equipped with these tools were efficiently constructed at JRR-3 in Japan Atomic Energy Research Institute (JAERI), Japan and they have finished many protein crystallographic measurements and interesting results have come one after another. At the same time a method of growing large protein single crystals and a database of hydrogen and hydration have also been developed. In the near future, a pulsed neutron diffractometer for biological macromolecules has been proposed at J-PARC in JAERI.

Study of material changes of SINQ target rods after long-term exposure by neutron radiography methods

This paper describes the results of non-destructive investigations by indirect neutron radiography methods obtained at the facility NEUTRA [Nondestruct. Testing Eval. 16 (2000b) 203], spallation neutron source SINQ [Operating experience and development projects at SINQ, PSI Report 98-04, ISSN 1019-0643]. Target rods from the second SINQ metal target were removed after 6 Ah of proton beam exposure and studied under well-shielded conditions. No real damage was found at one of the 11 observed rods and one tube. However, hydrogen accumulation could be identified inside the zircaloy rods and the steel rods as well. Whereas the hydrogen has a homogenous distribution in Zr (with the peak value near the centre of the applied beam), the steel samples show clusters of hydrogen near the edge of the Zr cladding. Lead (in steel cladding) was found modified by accumulations of spallation products, mainly mercury. In the radiography images, a depression of the neutron field was observed due to the absorption by mercury. The applied method with Dy and In as neutron converters and imaging plates [Nucl. Instrum. Methods 377 (1996) 119] as secondary detectors seems to be optimal for such kind of investigations, especially when quantitative considerations have to be made.

Characteristics of SrBPO 5:Ce 3+ based materials as a neutron storage phosphor

Characteristics of SrBPO 5:Ce 3+ based materials have been investigated as a neutron storage phosphor. The authors found that the SrBPO 5:Ce 3+ phosphor shows photostimulated luminescence (PSL) by illumination with 635 nm laser light after neutron irradiation. The PSL yields of SrBPO 5:Ce 3+ phosphor were increased by adding SrF 2. The red laser seemed to be efficient to produce PSL signal from the results of PSL excitation spectrum measurement. The PSL yields, per unit neutron fluence, of SrBPO 5:Ce 3++SrF 2 sample were proportional to E −0.5, where E is neutron energy. The S γ/ S n ratio of the phosphor was one order of magnitude lower compared to that of a commercially available imaging plate, where S γ and S n are the gamma and neutron sensitivities, respectively. The low S γ/ S n ratio indicates that the phosphor has good gamma-ray rejection characteristics as a neutron detector. The phosphor might be a candidate for a new neutron imaging plate having less gamma-ray sensitivity.

Prospects for efficient detectors for fast neutron imaging

A physical model describing in detail the process of fast neutron imaging in luminescent screens is presented. The detection quantum efficiency, luminosity and inherent spatial resolution of the screen were calculated using this model. Properties of transparent and disperse screens were compared. Two imaging systems were suggested to improve the detection efficiency and spatial resolution. A stack consisting of alternating neutron converters and image plates can help in obtaining both high spatial resolution and efficiency. A system containing a screen of special form and a diaphragm can be of use especially in the case of the fan beam.

Trial of very cold neutron radiography in Kyoto University reactor

A practical very cold neutron (VCN) radiography using a neutron imaging plate was carried out in VCN facility, Kyoto University Reactor (KUR: 5 MW). The neutron flux from the VCN bender with the characteristic wavelength of 4.8 nm gives a good image with 5 min irradiation time when CNS was operated. The macroscopic total cross sections of water were measured by imaging plates. It is Σ th=0.87 cm −1 measured in KUR E2 thermal neutron radiography facility and that of VCN is Σ VCN=9.4 cm −1. The resolution of water thickness is less than 0.1 mm for VCN radiography and close to the positional resolution of an imaging plate. VCN radiography can show the change of water quantity in gypsophila during a drying procedure.

Performance comparison of neutron and X-ray sensitive photo-stimulated imaging plates

Statistical characteristics of photo-stimulated luminescent (PSL) signals are studied using thermal neutrons, X- and γ-rays. It is shown that the statistical fluctuation of PSL is described simply by the PSL 1 1 Here, the word PSL is used to express a quantity of observed PSL signal, where PSL is a simple abbreviation of photo-stimulated luminescence, and expressed as a unit of the PSL value. value itself and is independent of radiation type, except for short-range high-LET particles. However, it is expected that the spatial resolution should be affected if the range of electrons or secondaries were much longer than the instrumental resolution (pixel size). When output PSL signals are compared between X- and γ-rays, the PSL values were proportional to the exposed air dose, independent of X-ray energy. However, signals from 60Co γ-rays were ∼1% of 22–40 kV X-ray output at the same dose.

Novel type of neutron image plates based on KCl:Eu 2+–LiF

Neutron image plates (NIP) provide a mean for the two-dimensional, position-sensitive detection of neutrons. They combine the advantages of a large dynamic range (up to 5 orders of magnitude), good spatial resolution (⩽300 μm) and large detection areas. NIPs are used at various instruments for powder or single-crystal diffraction in numerous radiation facilities. They have also found an application in neutron radiography and can be used for small-angle neutron scattering (SANS) such as at the Structure Powder DIffractometer (SPODI) at the FRM-II. In this study, the resolution of a novel type of ceramic NIPs based on KCl:Eu 2+–LiF is presented and simulations on the applicability of NIPs for neutron detection at the SANS apparatus of SPODI are reported.

New Facilities Expand Protein Crystallography Opportunities

The story “Neutron Diffraction Overcomes Flux Limits to Resolve a Large Protein Structure” (Physics Today, Physics Today 0031-9228 56 11 2003 17 https://doi.org/10.1063/1.1634521. November 2003, page 17 ) captures the excitement that has been generated in the structural biology community by recent results from neutron diffraction studies of large protein structures. As the scientists who built and operate the protein crystallography station (PCS) featured in the report, we felt compelled to write in order to avoid any misunderstanding about the role of the PCS in the development of neutron protein crystallography. Experiments in the late 1960s led to a neutron protein crystallography program at the reactor run by Brookhaven National Laboratory (BNL); that program provided important insights into the structure and function of a number of proteins. A similar program was started at the Institut Laue–Langevin (ILL) reactor in France in the 1980s, and another in the 1990s at the reactor run by the Japan Atomic Energy Research Institute (JAERI). The BNL reactor experienced frequent shutdowns in the 1990s, including its permanent shutdown in 1996. Those incidents, coupled with the shutdown of the ILL reactor in 1991, terminated neutron protein crystallography in North America and Europe for most of the 1990s.After the ILL restarted in 1995, a new type of protein crystallography station, the Laue diffractometer (LADI), was built; it uses the Laue method and the detector technology of neutron image plates. The image plate technology was developed at JAERI on another new protein crystallography station called BIX-3. The two stations have recently started to produce results.The construction of the PCS at the Los Alamos Neutron Science Center has added to the rebirth of this field. The PCS explores the capabilities of spallation neutrons. Next-generation spallation sources are being built throughout the world and offer the promise of significant gains (in performance and also an increase in the number of protein crystallography stations).We must emphasize that the increasing availability of optimized neutron protein crystallography stations in general, and not the unique capabilities of the PCS, has made possible a number of recent neutron diffraction studies of large proteins. Readers who are interested in carrying out experiments are welcome to contact us for information on the proposal process and for technical advice.© 2004 American Institute of Physics.

中性子科学への招待（３）中性子単結晶構造解析，生物回折計

Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins and nucleic acids, and the development of the neutron imaging plate (NIP) became a breakthrough event in neutron protein crystallography. A high resolution neutron diffractometers dedicated to biological macromolecules (BIX-3, BIX-4) with the NIP have been constructed at Japan Atomic Energy Research Institute. The detailed structure of the diffractometer and the systematic procedure of the neutron diffraction experiment from the crystallization of a large single crystal to the data collection and the data processing, and the future prospect of the neutron diffractometry in proteins will be presented.

Imaging of Rabbit VX-2 Hepatic Cancer by Cold and Thermal Neutron Radiography

Neutron radiography is based on differences in neutron mass attenuation coefficients among the elements and is a non-destructive imaging method. To investigate biomedical applications of neutron radiography, imaging of rabbit VX-2 liver cancer was performed using thermal and cold neutron radiography with a neutron imaging plate. Hepatic vessels and VX-2 tumor were clearly observed by neutron radiography, especially by cold neutron imaging. The image contrast of this modality was better than that of absorption-contrast X-ray radiography.

Characteristics of a SrBPO/sub 5/:Eu/sup 2+/ material as a neutron storage phosphor

Characteristics of a SrBPO/sub 5/:Eu/sup 2+/ material have been investigated as a neutron storage phosphor. The authors found that this phosphor shows photostimulated luminescence (PSL) by illumination with 635 nm laser light after neutron irradiation. The light with shorter wavelength than 635 nm seemed to be more efficient to produce PSL signal. The optimal concentration of Eu was 2% (mol %). The phosphor might be usable in a high gamma-ray field. The fading characteristics were similar to those of a commercially available neutron imaging plate. Using a disk-like sample, a collimated neutron beam image was clearly obtained by scanning focused laser light on it. The spatial resolution of 0.4 mm was obtained from the Edge Spread Function measurement.

Application of hydrogen analysis by neutron imaging plate method to Zircaloy cladding tubes

Effectiveness of neutron imaging plate (NIP) method for hydrogen analysis is investigated by using standard samples with known hydrogen concentrations. A relationship between hydrogen concentration in Zircaloy tubes and numerical data in the NIP images was obtained by image analysis process. By using the relationship, local hydrogen concentrations in segregated tubes with heterogeneous hydrogen distribution were estimated in a small area; 0.1 × 0.1 mm 2. Contribution of an oxide film in the tubes to the images is also investigated by using oxidized samples with and without hydrides. In the NIP images of the oxidized samples, oxide film was not recognized in the images of the sample. Results of numerical analysis also show no effect of the oxide film. These results show that the effect of oxygen in the image can be neglected when hydrogen analysis is performed on the Zircaloy tube with oxide film and hydrides by NIP method.

High resolution neutron protein crystallography. Hydrogen and hydration in proteins

Abstract Neutron diffraction provides an experimental method of directly locating hydrogen atoms in proteins, and the development of the neutron imaging plate (NIP) became a breakthrough event in neutron protein crystallography. The general features of the NIP are reviewed. A high resolution neutron diffractometer dedicated to biological macromolecules (BIX-3) with the NIP has been constructed at Japan Atomic Energy Research Institute and this has enabled 1.5 Å resolution structural analyses of several proteins to be carried out. The specifications of BIX-3 and LADI (a quasi-Laue type diffractometer installed in the Institut Laue-Langevin) are compared. The crystal structures of myoglobin, wild type rubredoxin and a mutant of rubredoxin have been carried out using BIX-3. From these studies, several topics, such as the location of hydrogen bonds and certain acidic hydrogen atoms, the identification of methyl hydrogen atoms, details of H/D exchange and dynamical behavior of hydration structures have been investigated, and important information has been extracted from the structural results. Finally, a systematic procedure to grow large single crystals of proteins or nucleic acids is described.

A Study on Application of Area Detector to Neutron Stress Measurement

A fundamental study was carried out on an application of an area detector to neutron stress measurement. A neutron image plate (NIP) was used in this experiment to obtain neutron diffraction rings of polycrystalline steel specimen. The diffraction data were stored on a NIP and were converted to digital image data. Strains were obtained from these data and were analyzed to determine stress using the cosα method. Though these stresses were different from applied stresses, they increased in proportion to applied stresses. Namely, the differences between measured and applied stresses were almost constant during loading. Based on these experimental results, two practical methods were proposed for determining exact stress using a NIP. The stresses obtained using one of these methods showed good agreement with applied stresses. From these results, it is concluded that we can obtain mean stress in materials using neutron diffraction technique with an area detector.

Development of neutron image plate for low-flux measurements

The results of an experimental test for the performance of a commercially available neutron-sensitive image-plate detector are presented. The particular aim of the experiments is to study the nature of noise in a neutron image obtained under the real conditions of a reactor hall. The most significant component of noise was found to be an external γ-ray background. The γ-ray dose of 1 μS/h leads to a noise in a neutron image with a neutron equivalent of about 1.2 n/cm2 s , which is comparable to magnitudes of weak diffraction peaks and diffuse scattering at thermal neutron scattering experiments. The high sensitivity of image plates to γ-rays results from the high charge density of storage-phosphor (BaFBr:Eu2+) and neutron-converter (Gd2O3) materials used in commercially available neutron image plates. The possibility of the use of 6LiF as a neutron converter instead of Gd2O3 to reduce the γ-ray sensitivity is discussed.