Analysis of Spent Nuclear Fuel Imaging Using Multiple Coulomb Scattering of Cosmic Muons
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Engineering↗
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Image fusion for neutron tomography of nuclear fuel
Image fusion, the process of combining different images together, can be useful to create a more complete picture. In this work, image fusion is applied to neutron tomography of nuclear fuel with the goal of enhancing the information obtained about the fuel. Different reconstruction methods, such as Feldkamp, Davis and Kress filtered back projection and Simultaneous Reconstruction Technique, were combined to enhance image quality. This methodology was shown to reduce noise and ring artifacts without sacrificing sharp edges, allowing for a more accurate representation of sample geometry. Technique enhancements and future applications for the neutron imaging community are also discussed.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Nuclear imaging of the fuel assembly in ignition experiments
First results from the analysis of neutron image data collected on implosions of cryogenically layered deuterium-tritium capsules during the 2011-2012 National Ignition Campaign are reported. The data span a variety of experimental designs aimed at increasing the stagnation pressure of the central hotspot and areal density of the surrounding fuel assembly. Images of neutrons produced by deuterium–tritium fusion reactions in the hotspot are presented, as well as images of neutrons that scatter in the surrounding dense fuel assembly. The image data are compared with 1D and 2D model predictions, and consistency checked using other diagnostic data. The results indicate that the size of the fusing hotspot is consistent with the model predictions, as well as other imaging data, while the overall size of the fuel assembly, inferred from the scattered neutron images, is systematically smaller than models' prediction. Preliminary studies indicate these differences are consistent with a significant fraction (20%–25%) of the initial deuterium-tritium fuel mass outside the compact fuel assembly, due either to low mode mass asymmetry or high mode 3D mix effects at the ablator-ice interface.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Muon-Computed Tomography using POCA Trajectory for Imaging Spent Nuclear Fuel in Dry Storage Casks
Cosmic ray muon-computed tomography (μCT) is a new imaging modality with unique characteristics that can be particularly important for applications in nuclear proliferation detection and international treaty verification. Using cosmic ray muons for nuclear security presents several potential advantages. Among others, muons are generated naturally in the atmosphere, can penetrate high-density materials, and are freely available. No radiological sources are required and consequently there is no associated radiological dose. Recently, the feasibility of using muons for imaging spent nuclear fuel stored in shielded casks has been explored and has been proved beneficial. However, challenges in μCT imaging include low muon flux of ~10,000 muons/m2/min, the effects of multiple Coulomb scattering (MCS) blurring the image, and inefficiency in being able to use all recorded muons for imaging. In this paper, we argue that the use of muon tracing should produce tomographic muon images with improved quality – or more quickly for the same image quality – compared to the case where conventional methods are used. In our paper, we report on the development and assessment of a novel muon tracing method for μCT. The proposed method back projects the muon’s scattering angle into each pixel crossed by its PoCA trajectory then forward projects the variance of the scattering angle in each pixel to detector bins along the muon’s incident horizontal direction. Two scenarios were simulated to assess the expected detection capability of this proposed method. GEANT4 was used to model the main characteristics of 1-60 GeV muons through matter. The simulated images showed an expected improvement in resolution and a reduced the reliance on the muon momentum information compared to a more conventional muon tomography method.
Liu, Zhengzhi↗
Creation of a Geant4 Muon Tomography Package for Imaging of Nuclear Fuel in Dry Cask Storage
This is the final report of the NEUP project “Creation of a Geant4 Muon Tomography Package for Imaging of Nuclear Fuel in Dry Cask Storage”, DE-NE0000695. The project started on December 1, 2013 and this report covers the period December 1, 2013 through November 30, 2015. The project was successfully completed and this report provides an overview of the main achievements, results and findings throughout the duration of the project. Additional details can be found in the main body of this report and on the individual Quarterly Reports and associated Deliverables of the project, uploaded in PICS-NE.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Investigation of Imaging Spent Nuclear Fuel Dry Casks using Cosmic Ray Muons
Recently, the use of cosmic ray muons for cargo scanning applications has been demonstrated and muons have been shown to have the potential to allow for nondestructive assessment of nuclear material accountancy. Relativistic muons have the ability to penetrate dense materials and monitoring the subsequent scattering of muons can provide information about the structure and composition of materials stored in cargo containers. The suitability of cosmic muons for a number of monitoring and imaging applications has been investigated over the years and includes applications to archaeology, volcano imaging, material identification and medical diagnosis. Novel applications of cosmic ray muons have been proposed for examination of comatose patients towards bone density monitoring and also for determination of the molten nuclear fuel location in nuclear reactors having suffered from the effects of a severe accident similar to the one happened in Fukushima. There is a need to develop a capability to monitor nuclear waste and investigate whether the stored content agrees with facility declarations to allow proliferation detection and international treaty verification. Monitoring nuclear waste and controlling nuclear material at its source is one of the main strategies to minimize the risks of nuclear proliferation and reduce potential homeland threats. Since the early 1950's, when the first nuclear power plant began to produce electricity, approximately 65,000 metric tons of spent nuclear fuel have been generated, 25% of which are under dry storage conditions. After the spent nuclear fuel has been placed inside the dry cask, the cask is welded, not allowing for visual inspection. During the long storage life of the cask, intermediate handling and transportation activities take place which does create concerns regarding fuel integrity. Accidents and natural disasters also contribute to this concern. Previous work on spent nuclear fuel dry cask monitoring using muons has shown that the muon scattering distributions are adequately separated and a and a decision rule derived from Bayes' Theorem rendering the classification of different dry casks feasible. Muons present significant advantages over the existing imaging techniques such as the utilization of the passive nature of muons, the lack of radiological sources and consequently the absence of any artificial radiological dose. In the present work, a methodology is developed to demonstrate the applicability of muons for imaging of spent nuclear fuel dry casks. Purpose is to use muons to differentiate between spent nuclear fuel dry casks with different amounts of loading. Monte Carlo simulations of dry casks with different spent nuclear fuel loading are performed to simulate the passage of polyenergetic muons having energies in the range of 1-60 GeV through matter. A 'Muon Generator' is developed to generate muons that follow the actual sea level energy distribution. The 'Muon Generator' is validated against a series of actual spectrum measurements and then coupled with the Monte Carlo particle transport code GEANT4. The accumulated dataset of scattering angles were processed with the Point-of- the-Closest-Approach (PoCA) imaging algorithm and the obtained images demonstrate that an empty dry cask can be clearly distinguished from a half-loaded or a fully loaded one. The apparent separation of the images demonstrates that the muon scattering can be used as a feature for imaging spent nuclear fuel dry casks. (authors)
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
AFIP-7 Tomography – 2013 Status Report
This project seeks to assess the geometric stability of the U-Mo monolithic fuel system by evaluating the radiation-induced changes in the AFIP-7 experiment device. Neutron radiography and computed tomography (CT) provide valuable information about the post-irradiation condition of the fuel specimen. Tomographic reconstructions of the AFIP-7 fuel element will be analyzed to assess the geometric condition of the element after irradiation and provide information regarding the condition of the fuel, including gross geometric defects, bowing, twist, plate buckling, cracks, and other defects. The INL, in collaboration with Oregon State University (OSU), Missouri University of Science and Technology (Missouri S&T), and Real Time Tomography, is developing advanced neutron detector systems and tomographic reconstruction techniques to evaluate the AFIP-7 fuel element. Neutron computed tomography using the current neutron radiography technique available at the Neutron Radiography reactor (NRAD) is impractical due to the long time and high cost to produce a set of images for tomographic reconstruction. Advanced neutron radiography systems such as the micro-channel plate (MCP) detector and neutron computed radiography (CR) may reduce the time and cost of acquiring images for neutron CT. The MCP detector system tested at OSU and Missouri S&T provides neutron radiographs and has lower gamma sensitivity compared to other digital acquisition image systems. However, some significant, but not prohibitive, challenges must be overcome to make its use for imaging nuclear fuel more practical. Images taken with the MCP require significant image processing to reduce distortions and correct for the dynamic detector response. Also, the small active area of the detector (~30 mm diameter) requires the collection and combination of several images of a specimen, which may become time-consuming. The MCP is tested in low gamma dose environments, but should also be tested in the gamma field at the INL. In addition to the MCP detector system, the INL is developing neutron computed radiography (CR), which uses the same foil transfer method currently employed at the NRAD, but replaces the film with a photostimulable storage phosphor imaging plate that is sensitive to the decay radiation from the activated transfer foils. Preliminary tests show that neutron CR provides lower, but comparable spatial resolution properties to film radiography images using the transfer method technique already employed at the NRAD. However, there are many factors that affect the spatial resolution of neutron CR that can be adjusted and possibly provide spatial resolution properties that exceed film radiography. The reduction in cost of neutron CR may be significant, which would make neutron imaging more appealing to programs that would benefit from this rare and valuable capability. Because transfer method neutron radiography is expensive and time-consuming, acquisition of a full set of radiographs for tomographic reconstruction is impractical. The INL is developing tomographic reconstruction techniques that require only a small set of radiographs of the AFIP-7 fuel element. These tomosynthesis techniques are tested using archived radiographs of TREAT experiments for CT as a proof of principle. These same techniques are applied to radiographs taken with an MCP detector of a mock-up of the AFIP-7 geometry. Acquisition angle should at least match the curvature of AFIP-7 plates. Lateral (in-plane) reconstruction resolution will be best when the projection angles include views at or near the desired reconstruction view angles. The ends of the fuel plates are angled at ±17.7° relative to the center of the plate. Increasing the number of projections is desirable, but given the constraint of minimizing the number of projections, the projection acquisition angle should also span at least ±17.7° to optimize the lateral resolution of the angled reconstruction planes used to visualize the gaps at the ends of the fuel plates. If possible, enough projections should be used within the initial acquisition angle of 35.4° (±17.7°) to bring the projection angular sampling closer to 1°. Further testing will determine a more specific recommendation for the number and angular distribution of neutron radiographs that will produce the highest quality tomographic reconstruction of the AFIP-7 fuel element.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Muon-Computed Tomography using POCA Trajectory for Imaging Spent Nuclear Fuel in Dry Storage Casks
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Liu, Zhengzhi↗
Detecting and imaging stress corrosion cracking in stainless steel, with application to inspecting storage canisters for spent nuclear fuel
Abstract not provided
Remillieux, Marcel C.↗
Characteristics of Muon Computed Tomography of Used Fuel Casks Using Algebraic Reconstruction
Cosmic raymuons passing through matter lose energy from inelastic collisions with electrons and are deflected from nuclei due to multiple Coulomb scattering (MCS). The recent developments in position sensitive muon detectors that can measure incoming and outgoing trajectories of individual muons indicate that MCS could be an excellent candidate for spent nuclear fuel imaging. The main purpose of this paper is to evaluate tomographic scanning of spent nuclear fuel stored within vertical and horizontal dry storage casks. A quantitative analysis of the characteristics of images obtained with filtered back projection (FBP) and algebraic reconstruction techniques (ART) are presented herein, as such a comparison has not been carried out in the past. FBP is a fast tool to determine object boundaries. ART can include muon path models and prior knowledge that can improve resolution and reduce measurement time. The results demonstrate that missing fuel assemblies can be identified with more than 5 projections and that use of muon momentum significantly increases image resolution. It is expected that MCS can be used to successfully reconstruct the dry cask contents and allow identification of all described scenarios in hours. It is also expected that when total variation minimization and a non-local mean filter are applied, ART may yield much better image quality than FBP.
Liu, Zhengzhi↗
Benefits of utilizing CellProfiler as a characterization tool for U–10Mo nuclear fuel
Automated image processing techniques have the potential to aid in the performance evaluation of nuclear fuels by eliminating judgment calls that may vary from person-to-person or sample-to-sample. Analysis of in-core fuel performance is required for design and safety evaluations related to almost every aspect of the nuclear fuel cycle. This study presents a methodology for assessing the quality of uranium–molybdenum fuel images and describes image analysis routines designed for the characterization of several important microstructural properties. The analyses are performed in CellProfiler, an open-source program designed to enable biologists without training in computer vision or programming to automatically extract cellular measurements from large image sets. The quality metric scores an image based on three parameters: the illumination gradient across the image, the overall focus of the image, and the fraction of the image that contains scratches. The metric presents the user with the ability to ‘pass’ or ‘fail’ an image based on a reproducible quality score. Passable images may then be characterized through a separate CellProfiler pipeline, which enlists a variety of common image analysis techniques. The results demonstrate the ability to reliably pass or fail images based on the illumination, focus, and scratch fraction of the image, followed by automatic extraction of morphological data with respect to fission gas voids, interaction layers, and grain boundaries. - Graphical abstract: Display Omitted - Highlights: • A technique is developed to score U–10Mo FIB-SEM image quality using CellProfiler. • The pass/fail metric is based on image illumination, focus, and area scratched. • Automated image analysis is performed in pipeline fashion to characterize images. • Fission gas void, interaction layer, and grain boundary coverage data is extracted. • Preliminary characterization results demonstrate consistency of the algorithm.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Evaluation of Desiccation Behavior in Basalt Microfiber–Reinforced Bentonite Clay for Geological Repositories of Nuclear Spent Fuel Using Digital Image Correlation
ABSTRACT Secure storage of nuclear spent fuel (NSF) is of great concern for protecting public health and safety. The preferred long-term solution is underground containment in geological repositories, where one or more engineered barrier materials (EBM) encapsulate the NSF and separate it from the natural rock. Bentonite clay is commonly used as an EBM due to its many advantageous properties including low hydraulic conductivity, which ensures limitation of water infiltration to the system and the subsequent risk of corrosion in NSF canisters. However, bentonite clay subjected to heating from nuclear decay may form desiccation cracking. This study conducted disk-shaped free shrinkage tests and ring-shaped restrained shrinkage tests of bentonite clay samples reinforced with basalt microfibers. Digital image correlation was used as a noncontact full-field displacement measurement to track the time-evolving shrinkage and desiccation cracking phenomena and make quantified comparisons between plain bentonite and bentonite with varying contents of basalt microfibers (i.e., 0.0, 0.5, 1.0, and 1.5 % wt.). Results indicate that plain bentonite and basalt microfiber-reinforced samples showed similar free shrinkage behavior, while desiccation cracking behavior was significantly altered by adding basalt microfibers. Microfiber reinforcement effectively reduced major cracks through a “crack-bridging” effect while causing minor cracks to initiate earlier and at higher moisture contents than plain bentonite. Results infer that reinforcing plain bentonite with inorganic microfibers can potentially control desiccation cracking, leading to safer and improved nuclear waste management.
Materials Science↗
Classification and imaging of spent nuclear fuel dry casks using cosmic ray muons - 132
The present work explores alternative approaches for in situ monitoring with near real-time data analysis and imaging of dry casks using muons. Monitoring can provide useful signals about the cask contents in a yes/no decision format faster and with fewer muons than traditional imaging. Imaging can be performed as a second step in this process if specific information about the location of the fuel assemblies is needed. To explore and analyze these two modalities, simulations of muon scattering and displacement were performed for various scenarios, including vertical and horizontal fully loaded dry casks, half-loaded dry casks, dry casks with one row of fuel assemblies missing, dry casks with one fuel assembly missing, and empty dry casks. This work demonstrates monitoring can provide fast and reliable indication about the contents of the cask. For 100,000 muons, a few minutes of measurement time with a 3.6 m{sup 2} detector at a 45 deg. zenith angle, 90% detection probability for missing fuel assemblies can be achieved with a false alarm rate lower than 1%. If a positive signal is detected, then longer measurements can be performed and coupled with muon imaging algorithms to determine the location of missing nuclear material. In these cases, transmission muon radiography can produce images of acceptable resolution for all scenarios. In the horizontal dry cask case, all scenarios can be identified and separated adequately. In the vertical dry cask case, similar conclusions can be drawn, but because of shadowing from other fuel assemblies, the location of a missing fuel assembly cannot be identified in the 2-D transmission map. However, views from different directions may resolve this. (authors)
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
Resolution Limits of Near IR and IR Thermography Applied to Imaging Thermal Heterogeneities in Nuclear Fuel Surrogate Materials
ABSTRACT The main goal of the project is: To develop an IR thermographic method to monitor fuel pellet cracking inside the hostile environment of the nuclear core. This method will use a high temperature and radiation resistant fiber optic bundle to monitor the fuel pellet inside the core and transmit the information outside to an IR camera. This method will give a visual cue (using IR video) as to when the crack started to form and how it progresses. To achieve this goal, we identified the following as major milestones of the project: 1. Perform 1D modeling of temperature and blackbody radiation intensity across a crack. 2. Image a crack on a fuel cell surrogate using an IR camera with free-space optics and high power laser setup. 3. Simulate cracking in the surrogate sample through inductive heating method, and demonstrate imaging crack formation using the free-space optics setup. 4. Determine parameters for a suitable fiber optic bundle compatible with the IR camera based on the results from the free-space optics experiments. 5. Demonstrate imaging using fiber bundle and integrate viewing system with nuclear core at INL. This report focuses on Goals 1-3. We have successfully achieved Goals 1-3 and are making steady progress towards achieving Goals 4-9. Goals 2 and 4 are very similar and require 2 basic parts: the imaging system and the method to crack the fuel surrogate to replicate the fuel pellet cracking in the nuclear reactor core. The following sections describe the 1D modeling of temperature and blackbody radiation intensity across a crack (Goal 1), procedure to create crack on fuel surrogates and results (Goals 2 and 3), and the IR imaging system and results (Goal 2).
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Cosmic Ray Muon Imaging of Spent Nuclear Fuel in Dry Storage Casks
In this paper, cosmic ray muon radiography has been used to identify the absence of spent nuclear fuel bundles inside a sealed dry storage cask. The large amounts of shielding that dry storage casks use to contain radiation from the highly radioactive contents impedes typical imaging methods, but the penetrating nature of cosmic ray muons allows them to be used as an effective radiographic probe. This technique was able to successfully identify missing fuel bundles inside a sealed Westinghouse MC-10 cask. This method of fuel cask verification may prove useful for international nuclear safeguards inspectors. Finally, muon radiography may find other safety and security or safeguards applications, such as arms control verification.
98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
Simulated imaging of spent nuclear fuel using associated-particle-neutron-induced gamma rays
Not Available
Instruments & Instrumentation↗
Classification and Imaging of Spent Nuclear Fuel Dry Casks Using Cosmic Ray Muons
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Chatzidakis, Stylianos↗