Thermal Neutron Imaging Using University Of Florida Training Reactor (#3516)
J. K. Nimmagadda1, K. Jordan1, A. Enqvist1, J. E. Baciak1
1 University of Florida, Nuclear Engineering Program, GAINESVILLE, Florida, United States of America
Thermal neutron imaging technique was developed using the 100 kW UFTR and a CCD neutron camera at the University of Florida. The 200 X 200 mm scintillator used in the neutron camera was a 0.2 mm thick 6LiF/ZnS screen. The maximum resolution of the camera was ~100 μm. The thermal column beam port of the reactor was modified for collimation and was used to produce the neutron images. Different reactor power levels were chosen depending on the samples ranging from 100 W to 4000 W. Thermal neutron images of different sample objects like flower bouquet inside a lead cask, ASTM standards, turbine blade, small gearbox and water valve were acquired. The acquisition times range from 2 to 5 min for the samples discussed in this paper.
Keywords: neutron camera, reactor, thermal neutron images
Spectroscopic Fast Neutron Transmission Imaging in a Treaty Verification Setting (#2180)
K. Ogren1, J. Nattress1, I. Jovanovic1
1 University of Michigan, Department of Nuclear Engineering and Radiological Science, Ann Arbor, Michigan, United States of America
Measurements of the geometric configuration of objects and their fissile content are needed for nuclear treaty verification purposes. However, such measurements are often restricted because they involve the collection of classified information. We offer a simple method based on monoenergetic fast neutron transmission which could be applied to a template-based zero-knowledge protocol. We experimentally demonstrate the capability of this method to realize crude imaging of the geometric configuration of special nuclear material, confirm its fissionable content, and obtain information on the approximate relative fissile mass. Using neutrons from DD and DT reactions and a one-dimensional array of liquid scintillation detectors, we perform spectroscopic neutron imaging of up to 13.7 kg of highly enriched uranium in a spherical geometry and confirm the presence of fissionable material based on the measurement of high-energy prompt fission neutrons, including estimating the quantity of material from the comparison of measured and predicted fission neutron emission rate. We also show an example of detection of material diversion using both transmission imaging and fission neutron counting methods. The combination of crude imaging and fissionable material detection and quantification in a simple approach may be attractive in certain treaty verification scenarios.
Keywords: treaty verification, neutron transmission imaging, pulse shape discrimination
Detector Performance for Fast Neutron Radiography and Computed Tomography (#2158)
J. F. Hunter1, C. Aedy2, R. D. Edwards2, R. O. Nelson1, A. C. Madden1, N. M. Winch1
1 Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
Neutron radiography has long been used as a complimentary imaging technique to x-ray radiography. Xray radiography is ideal for imaging relatively thin objects, and higher-Z objects in low Z materials. The smaller interaction cross section of neutrons in high-Z materials (as compared to x-rays) allows neutron radiography to image low-Z materials through high-Z materials. Applications of neutron radiography include non-destructive testing, part validation, weld inspection, and global security verifications. Thermal neutron imaging is the most common technique due to the availability of thermal neutron sources and good efficiency for detection. However, as with x-rays, thermal neutrons cannot penetrate dense and thick objects. Imaging with high energy neutrons can provide imaging contrast of heavily shielded materials that is unobtainable by x-rays or thermal neutrons. Fast neutron imaging is more difficult because fast neutron sources are scarce, large neutron scatter fields are produced when an object is placed in the neutron beam, and detector electronics must be removed from the neutron path, or be able to withstand large radiation doses. In addition, the transmission benefit of a lower interaction cross section for fast neutrons makes fast neutrons difficult to detect efficiently. To address some of these difficulties in imaging, a world class neutron radiography and computed tomography facility has been developed at the Los Alamos Neutron Science Center (LANSCE). LANSCE produces a fast neutron beam with an average energy of 40 MeV and a median energy near 5 MeV. Two fast neutron detector configurations recently were investigated for use in this facility, a flat panel with mounted ZnS scintillator, and a CCD camera optically coupled to variousscintillator screens. Results of the detector performance metrics such as the modulation transfer function,and the detective quantum efficiency are presented.
Keywords: Fast neutrons, radiography, Computed Tomography, Image Quality
The design of a photoneutron source for the drugs detection in a large-truck (#2891)
Y. Zhao1, 2, Y. Yang1, 2, Q. Liu1, 2, Z. Fang1, 2, Y. Fu1, 2
1 Tsinghua University, Department of Engineering Physics, Beijing, Beijing, China
A photoneutron source based system is proposed to address the problem of detecting drugs concealed in the large trucks. By utilizing the heavy water convertor to convert X-rays to photoneutrons, a photoneutron source with neutron yield higher than 1011 n/s can be realized with a 7 MeV/700 W e-LINAC. To meet the requirements of in situ application for the large-truck inspection, the photoneutron production, neutron moderation, and both X-rays and photoneutrons shielding are carefully researched to achieve a high analyzing sensitivity inside the truck, whereas at the same time maintain a low dose rate on the boundary of the control zone to ensure the public safety. A NaI(Tl) detector array is used to measure the thermal neutron induced radiative capture gamma-rays to analyze the concentrations and distributions of various elements of the inspected objects inside the truck. By analyzing the gamma-ray spectra of a 6.23 kg methamphetamine simulant shielded by various thickness of steel, the feasibility of this system to find the concealed Cl-rich drugs inside large trucks is confirmed by this research. The false positive and false negative rate can be as low as 0.1% even the methamphetamine simulant is shielded by a 5-cm-thick steel.
Keywords: drugs; photoneutron; large trucks; radiative capture;
Characterization of Advanced Scintillator Materials for Neutron Imaging in Inertial Confinement Fusion (#3699)
V. Geppert-Kleinrath1, T. Cutler1, C. Danly1, A. Madden1, F. Merrill1, J. Tybo1, P. Volegov1, C. Wilde1
1 Los Alamos National Laboratory, Los Alamos, New Mexico, United States of America
The LANL Advanced Imaging team is currently in the process of designing a novel neutron imaging system for the National Ignition Facility (NIF). The team has been providing 2D neutron imaging of the burning fusion fuel at NIF for years, revealing possible multi-dimensional asymmetries in the fuel shape of the inertial confinement fusion reactions, and therefore calling for additional views along new lines of sight. The selection of an ideal scintillator material for a position-sensitive detector system is the key component for the new design. The new imaging system will be along a shorter line of sight, requiring several technological challenges to be met: high spatial resolution, high light output, and fast scintillator response to capture a primary fusion neutron image as well as lower-energy down-scattered neutrons. A comprehensive study of advanced scintillator materials has been carried out at the Los Alamos Neutron Science Center and the OMEGA Laser Facility in Rochester, NY. Neutron radiography using a fast-gated CCD camera system delivers resolution and light output measurements. We conclude the feasibility of a monolithic scintillator over a pixelated counterpart for the novel imaging system, and present the first resolution measurement of a deuterated plastic scintillator – a promising candidate for the new design.
Keywords: neutron imaging, scintillators, ICF
Development of a Plastic Scintillation-based Detector for Real-Time Radioisotope Imaging of 32P Uptake in Plant Root Systems (#2459)
B. Kross1, S. J. Lee1, A. Llodra3, J. E. McKisson1, J. McKisson1, A. Pla-Dalmau2, A. G. Weisenberger1, W. Xi1, C. Zorn1
1 Jefferson Laboratory, Newport News, Virginia, United States of America
A real-time imaging system is being developed to allow plant scientists to track the nutrient flow in the plant roots and the associated fungi that grow near the roots. Specifically, phosphorus is a common element taken up as phosphate. Radioactive 32P can be used to study this system as it emits a short-range beta particle. A detector is being developed that consists of a crossed matrix of wavelength shifting fibers with small plastic scintillation beads located at the intersections of the fibers. Betas from 32P are detected in nearby scintillating beads and the blue emission is converted to a green emission in the fibers and piped to the corresponding photodetectors. The latter can be either arrays of silicon photomultipliers or a set of position sensitive photomultiplier tubes. A real-time image can be formed that allows the tracking of the 32P activity in the soil fungi and plant roots. This summary provides a description and basic characterization of the first prototype device.
Keywords: scintillator, beta detection, imaging, phosphorus-32, silicon photomultiplier