Nondestructive Examination Techniques Research Articles

Momentum informed muon scattering tomography for monitoring spent nuclear fuels in dry storage cask

Development of an effective monitoring method for spent nuclear fuel (SNF) in a dry storage cask (DSC) is important to meet the increasing demand for dry storage investigations. The DSC investigation should provide information about the quantity of stored SNF, and quality assurance of materials should be possible without opening the cask. However, traditional nondestructive examination (NDE) methods such as x-rays are difficult to deploy for DSC investigation because a typical DSC is intentionally designed to shield against radiation. To address this challenge, cosmic ray muons (CRMs) are used as an alternative NDE radiation probe because they can easily penetrate an entire DSC system; however, a wide application of muons is often hindered due to the naturally low CRM flux (~104 muons/m2/min). This paper introduces a newly proposed imaging algorithm, momentum-informed muon scattering tomography (MMST), and presents how a limitation of the current muon scattering tomography technique has been addressed by measuring muon momentum. To demonstrate its functionality, a commercial DSC with 24 pressurized light water reactor fuel assemblies (FAs) and the MMST system were designed in GEANT4. Three noticeable improvements were observed for MMST system as a DSC investigation tool: (1) a signal stabilization, (2) an enhanced capability to differentiate various materials, and (3) statistically increased precision to identify and locate missing FAs. The results show that MMST improves the investigation accuracy from 79 to 98% when one FA is missing and 51% to 88% when one-half FA is missing. The advancement of the NDE technique using CRM for DSC verification is expected to resolve long-standing problems in increasing demand for DSC inspections and nuclear security.

Damage Monitoring of Composite Adhesive Joint Integrity Using Conductivity and Fiber Bragg Grating

Adhesive joints possess a number of advantages over traditional joining methods and are widely used in composite structures. Conventional non-destructive examination techniques do not readily reveal joint degradation before the formation of explicit defects. Embedded fiber Bragg grating (FBG) sensors and the resistance of carbon nanotube (CNT)-doped conductive joints have been proposed to monitor the structural integrity of adhesive joints. Both techniques will be employed and compared in the current work to monitor damage development in adhesive joints under tensile and cyclic fatigue loading. Most of the previous works took measurements under an applied load, which by itself will affect the monitoring signals without the presence of any damage. Moreover, most FBG works primarily relied on the peak shifting phenomenon for sensing. Degradation of adhesive and inter-facial defects will lead to non-uniform strain that may chirp the FBG spectrum, causing complications in the peak shifting measurement. In view of the above shortfalls, measurements are made at some low and fixed loads to preclude any unwanted effect due to the applied load. The whole FBG spectrum, instead of a single peak, will be used, and a quantitative parameter to describe spectrum changes is proposed for monitoring purposes. The extent of damage is revealed by a fluorescent penetrant and correlated with the monitoring signals. With these refined techniques, we hope to shed some light on the relative merits and limitations of the two techniques.

Fast-neutron/gamma-ray radiography using a broad-energy neutron source

Transmission radiography is a well-established nondestructive examination technique with widespread application to fields ranging from medicine to security. Traditionally, inspection is performed using a single particle type (such as x-rays). However, the information available using a single probe for traditional radiography is limited. The present work evaluates material discrimination via transmission radiography using the attenuation ratio of monoenergetic gamma rays to a broad spectrum of fast neutrons. The method was assessed using an 241Am/Be radioisotope source that provides both 4.4 MeV gamma rays and a spectrum of fast neutrons up to 12 MeV. A total of 14 object configurations were measured: seven different materials each with two thicknesses (2.5 cm and 5 cm). The ability to distinguish materials was evaluated and shows more significant variation among atomic numbers than for high-energy x-rays alone, making it easier to distinguish between classes such as low-, mid-, and high-Z materials. These results suggest that superior material discrimination is also possible using a combination of monoenergetic gamma rays and broad-spectrum fast neutrons from a variety of nuclear reactions, such as 11B(d,nγ)12C, that could be implemented in future inspection systems.

Dimensional X-Ray computed tomography: Apparent feature form error and its effect on measurement tasks

X-ray computed tomography (XCT) provides a unique set of dimensional measurement capabilities suitable for assessing complex geometry. However, due to the origins of XCT as a medical imaging method and qualitative non-destructive examination technique, only recently has XCT been rigorously investigated as a dimensional metrology tool. Although the data produced via XCT may be leveraged with conventional coordinate metrology techniques, the instrument physics and volumetric reconstruction methods which govern the accuracy and precision of the data are complex, workpiece-specific, and non-negligible. In particular, there is minimal prior work which has studied complex multi-step metrology tasks such as datum reference frame (DRF) construction and feature position measurement. In this work, a qualified artifact was used to evaluate the fitness of XCT for such a task. Multiple XCT systems were used, and multiple instrument magnification levels compared. The form error of planar and cylindrical features was evaluated. Further, the influence of individual feature reconstruction on the development of datums and upstream position measurements was studied. It was found that negative, i.e., bore-like, and positive, i.e., pin-like configurations of certain features were subject to distinct XCT artifact effects which caused upstream measurement errors when these features were used to construct a DRF. High magnification and X-ray scatter produced high spatial frequency noise in surface reconstruction while beam hardening and beam penetration distance variation produced gross apparent form error. The latter was associated with greater measurement errors in feature position measurement within an DRF.

Novel Eddy Current Array Sensor Delivery Tool for Automated Nondestructive Examination of Spent Fuel Pool Liner

Abstract Inspection of a spent fuel pool (SFP) liner of a nuclear power plant is important to validate the integrity of this component to perform its intended function (e.g., confirm that there are not any defects in the pool liner). Eddy current array (ECA) testing offers a reliable and sensitive nondestructive examination (NDE) technique to inspect SFP liners but requires a delivery system to transport the ECA sensor to these hard-to-reach and harsh environment locations. This work presents an ECA sensor delivery tool design for use with inspection of an SFP. The design for a payload delivery tool proof-of-concept model is proposed that can transport an ECA sensor with positional feedback. The tool allows the sensor to traverse the wall of a nuclear SFP liner, with both horizontal and vertical motion capabilities to support positioning and inspection. The tool provides both manual and automatic operating modes with variable speeds. Computational-based simulations and analysis validate that the performance requirements for the ECA sensor delivery tool are satisfied to support inspection of an SFP liner upper region.

Examination and Characterization of Physical and Mechanical Properties of the ITER Central Solenoid Module Coils

The ITER Central Solenoid (CS) consists of a stack of six independent coil packs called modules. It features a total height of 18 m and a diameter of over 4 m. The modules are in an advanced stage of fabrication and testing by the US ITER Project Office (USIPO) and its subcontractor General Atomics (GA). A qualification module mockup at one to one scale but of reduced height was wound and Vacuum Pressure Impregnated (VPI) by GA to validate final manufacturing, using tooling and processes fully representative of a series module. The module was submitted to a thermal cycle down to the temperature of 4.5 K at which the coils will be cooled by supercritical helium. During plasma operation, the CS modules are subjected to a complex combination of static and dynamic forces. The understanding of the mechanical behaviour of the CS module coils is of paramount importance to analyse and predict the overall response of the CS stack. To this purpose, an extensive programme of investigation of the module mockup has been defined and applied. This allowed assessing, through examination and testing of a large number of VPI conductor array samples extracted from the mockup, the soundness of the coil through advanced non-destructive examination techniques including X-ray microtomography, dimensional metrology measurements and micro-optical observations. Moreover, additional testing of physical and mechanical properties carried out at room and cryogenic temperature allowed the behaviour of the conductor stacks to be assessed. The paper summarises the results of these investigations and their interpretation through mechanical analyses based on the individual properties of the coil constituents.

Materials for Sustainable Nuclear Energy: A European Strategic Research and Innovation Agenda for All Reactor Generations

Nuclear energy is presently the single major low-carbon electricity source in Europe and is overall expected to maintain (perhaps eventually even increase) its current installed power from now to 2045. Long-term operation (LTO) is a reality in essentially all nuclear European countries, even when planning to phase out. New builds are planned. Moreover, several European countries, including non-nuclear or phasing out ones, have interests in next generation nuclear systems. In this framework, materials and material science play a crucial role towards safer, more efficient, more economical and overall more sustainable nuclear energy. This paper proposes a research agenda that combines modern digital technologies with materials science practices to pursue a change of paradigm that promotes innovation, equally serving the different nuclear energy interests and positions throughout Europe. This paper chooses to overview structural and fuel materials used in current generation reactors, as well as their wider spectrum for next generation reactors, summarising the relevant issues. Next, it describes the materials science approaches that are common to any nuclear materials (including classes that are not addressed here, such as concrete, polymers and functional materials), identifying for each of them a research agenda goal. It is concluded that among these goals are the development of structured materials qualification test-beds and materials acceleration platforms (MAPs) for materials that operate under harsh conditions. Another goal is the development of multi-parameter-based approaches for materials health monitoring based on different non-destructive examination and testing (NDE&T) techniques. Hybrid models that suitably combine physics-based and data-driven approaches for materials behaviour prediction can valuably support these developments, together with the creation and population of a centralised, “smart” database for nuclear materials.

Hygrothermal Damage Monitoring of Composite Adhesive Joint Using the Full Spectral Response of Fiber Bragg Grating Sensors.

Adhesive joints in composite structures are subject to degradation by elevated temperature and moisture. Moisture absorption leads to swelling, plasticization, weakening of the interface, interfacial defects/cracking and reduction in strength. Moisture and material degradation before the formation of defects are not readily revealed by conventional non-destructive examination techniques. Embedded fiber Bragg grating (FBG) sensors can reflect the swelling strain in adhesive joints and offer an economical alternative for on-line monitoring of moisture absorption under hygrothermal aging. Most of the available works relied on the peak shifting phenomenon for sensing. Degradation of adhesive and interfacial defects will lead to non-uniform strain that may chirp the FBG spectrum, causing complications in the peak shifting measurement. It is reasoned that the full spectral responses may be more revealing regarding the joint’s integrity. Studies on this aspect are still lacking. In this work, single-lap joint composite specimens with embedded FBGs are soaked in 60 °C water for 30 days. Spectrum evolution during this period and subsequent tensile and fatigue failure has been studied to shed some light on the possible use of the full spectral response to monitor the development of hygrothermal degradation.

Adhesive Joint Integrity Monitoring Using the Full Spectral Response of Fiber Bragg Grating Sensors.

Although adhesive joining has many advantages over traditional joining techniques, their integrity is more difficult to examine and monitor. Serious structural failures might follow if adhesive joint degradation goes undetected. Available non-destructive examination (NDE) methods to detect defects are helpful in discovering defective joints during fabrication. For long-term monitoring of joint integrity, many of these NDE techniques are prohibitively expensive and time-consuming to carry out. Recently, fiber Bragg grating (FBG) sensors have been shown to be able to reflect strain in adhesive joints and offer an economical alternative for on-line monitoring. Most of the available works relied on the peak shifting phenomenon for sensing and studies on the use of full spectral responses for joint integrity monitoring are still lacking. Damage and disbonding inside an adhesive joint will give rise to non-uniform strain field that may chirp the FBG spectrum. It is reasoned that the full spectral responses may reveal the damage status inside the adhesive joints. In this work, FBGs are embedded in composite-to-composite single lap joints. Tensile and fatigue loading to joint failure have been applied, and the peak splitting and broadening of the full spectral responses from the embedded FBGs are shown to reflect the onset and development of damages. A parameter to quantify the change in the spectral responses has been proposed and independent assessment of the damage monitoring capability has been verified with post-damage fatigue tests.

STUDY ON IN-SERVICE INSPECTION PROGRAM AND METHOD FOR FUEL HANDLING SYSTEM OF RDE

One of the main programs that should be established on the designing process of the fuel handling system is to establish an in-service inspection program for maintaining the integrity of the system, structure and component during service lifetime. The most important role of in-service inspection is the nondestructive examination techniques. The objective of this study is to propose a preliminary program for examining the integrity of the fuel handling system during operation and determining the best method to confirm the defects. The proposed programs are described as follows, defining the operating environment of the fuel handling system, identifying the material characteristics during operation which indicates to promote the defects, and selecting the appropriate method of non-destructive examination and analysis technique for such kind of defects. The proposed in-service inspection program is expected to give significant additional value to the fuel handling system design of RDE.

The development of techniques to detect high temperature hydrogen attack – A mini review

High temperature hydrogen attack (HTHA) is classified as one of the problematic failure mechanisms which normally occurs in petrochemical refineries. It causes degradation in a material due to high temperatures and pressures that are involved. Carbon steel and low alloy steels are the materials that are most prone to this damage mechanism. The main challenge facing refineries is the early warning systems that can be used to detect this failure before it is at an advanced stage. Due to the challenges of HTHA inspection, several advanced non-destructive examination techniques have been developed over the years. This includes acoustic emission testing (AET), automated ultrasonic detection and classification (AUDC), and more, where many of these techniques are microstructural based. Although there have been several new developments for detecting this failure mechanism, some developments are more focused on continuous monitoring of material behaviour under operational conditions. However, most techniques being used are normally deployed to detect all possible material failures including corrosion. These techniques can’t be used as a stand-alone for HTHA detection due to complexity and the nature of data. This paper briefly reviews the techniques that have been developed to detect HTHA. The detection accuracy of the systems being developed, and the level of implementation are also discussed. The techniques used to track the sites of hydrogen in metals are also reviewed with the purpose of establishing whether those techniques can be used in monitoring the HTHA. This will assist in understanding the gaps around HTHA detection.

Independent component analysis for pulse compressed frequency modulated thermal wave imaging for inspection of mild steel

Non-destructive testing & evaluation plays a crucial role in various sectors for testing the reliability of materials. Of the different available non-destructive examination techniques, thermal non-destructive testing provides fast and remote inspection of the materials. Among various widely used thermal non-destructive testing techniques, frequency modulated thermal wave imaging gained its importance due to its higher test sensitivity and resolution. The adopted matched filter approach on the obtained temporal temperature distribution further concentrates supplied excitation energy into a narrow duration high peak power pulse. In this paper, the merits of the reconstructed high peak power pulsed data have been considered and emphasized in the context of independent component analysis. The obtained results clearly indicate that pulse compressed data improves defect detectability, reliability, memory usage, and computational complexity.

RADIOGRAPHIC EXAMINATION PROCEDURE AS NON DESTRUCTIVE TESTING METHOD IN PROCESS PIPING

Industry must have good quality for their services or products. One of the things that their have done is how to get the customer’s belief in their brand. Quality in every part has become the main case. Most of the companies in industry use metals as material to support their services. When the goods have been processed, it must continue with the testing. This is to prove that the goods have gone through the formation process fill in standard quality which required by the customer. There are two types of testing known as destructive testing and non-destructive testing. There are some of ways of non destructive testing methods on metals inspection has been applied in testing the quality of goods. Such as visual test, magnetic particle test, liquid penetrant, eddy current test, ultrasonic test, radiographic test in metals testing. Nondestructive testing (NDT) is the process of inspecting, testing, or evaluating materials, components or assemblies for discontinuities, or differences in characteristics without destroying the serviceability of the part or system. Radiographic Testing (RT) is a nondestructive examination technique that involves the use of either x-rays or gamma rays to view the internal structure of a component. In the petrochemical industry, Radiographic Testing is often used to inspect machinery, such as pressure vessels and valves, to detect for flaws. RT is also used to inspect weld repairs. Compared to other NDT techniques, radiography has several advantages. It is highly reproducible, can be used on a variety of materials, and the data gathered can be stored for later analysis.

Potential application of liquid dye penetrants for serial number restoration on firearms

Chemical reagents for serial number restoration are designed to exploit the plastic deformation zone below the obliterated serial number. Most techniques in operational use are variants of Fry’s Reagent. This technique uses toxic, corrosive chemicals and requires a skilful operator in the laboratory. Fry’s Reagent can also be destructive of the firearm due to rusting. In an attempt to find a non-toxic, non-destructive alternative to Fry’s Reagent, this project tested the use of liquid dye penetrants (LDPs), a non-destructive examination technique to detect cracks and imperfections used in the welding industry, for the restoration of obliterated serial numbers. Steel plates bearing an obliterated serial number with a range of obliteration depths were subjected to LDP treatment under various treatment conditions. The results using LDPs were negative for all obliteration depths and all test conditions attempted. Some of the serial numbers were subsequently restored successfully with Fry’s reagent, proving that the plastic deformation zone was present on the steel plates below the obliteration. Further work to develop a non-toxic, non-destructive serial number restoration process will be undertaken.

Probabilistic Fracture Mechanics for Heavy-Duty Gas Turbine Rotor Forgings

We developed and successfully applied a direct simulation Monte Carlo (MC) scheme to quantify the risk of fracture for heavy-duty rotors commonly used in the energy sector. The developed probabilistic fracture mechanics (FM), high-performance computing methodology, and code ProbFM routinely assess relevant modes of operation for a component by performing billions of individual FM simulations. The methodology can be used for new design and life optimization of components, as well as for the risk of failure RoF quantification of in service rotors and their requalifications in conjunction with nondestructive examination techniques, such as ultrasonic testing (UT). The developed probabilistic scheme integrates material data, UT information, duty-cycle data, and finite element analysis (FEA) in order to determine the RoF. The methodology provides an integrative and robust measure of the fitness for service and allows for a save and reliable operation management of heavy-duty rotating equipment.

Korean Round-Robin Tests Result for New International Program to Assess the Reliability of Emerging Nondestructive Techniques

Abstract The Korea Institute of Nuclear Safety, as a representative organization of Korea, in February 2012 participated in an international Program to Assess the Reliability of Emerging Nondestructive Techniques initiated by the U.S. Nuclear Regulatory Commission. The goal of the Program to Assess the Reliability of Emerging Nondestructive Techniques is to investigate the performance of emerging and prospective novel nondestructive techniques to find flaws in nickel-alloy welds and base materials. In this article, Korean round-robin test results were evaluated with respect to the test blocks and various nondestructive examination techniques. The test blocks were prepared to simulate large-bore dissimilar metal welds, small-bore dissimilar metal welds, and bottom-mounted instrumentation penetration welds in nuclear power plants. Also, lessons learned from the Korean round-robin test were summarized and discussed.

Evaluating quantitative 3-D image analysis as a design tool for low enriched uranium fuel compacts for the transient reactor test facility: A preliminary study

3-D image analysis when combined with a non-destructive examination technique such as X-ray computed tomography (CT) provides a highly quantitative tool for the investigation of a material's structure. In this investigation 3-D image analysis and X-ray CT were combined to analyze the microstructure of a preliminary sub-sized fuel compact for the Transient Reactor Test Facility's low enriched uranium conversion program to assess the feasibility of the combined techniques for use in the optimization of the fuel block fabrication process.The quantitative image analysis focused on determining the size and spatial distribution of the surrogate fuel particles and the size, shape, and orientation of voids within the compact. Additionally, the maximum effect of microstructural features on heat transfer through the carbonaceous matrix of the preliminary compact was estimated.The surrogate fuel particles occupied 0.8% of the compact by volume with a log-normal distribution of particle sizes with a mean diameter of 39μm and a standard deviation of 16μm. Roughly 39% of the particles had a diameter greater than the specified maximum particle size of 44μm suggesting that the particles agglomerate during fabrication. The local volume fraction of particles also varies significantly within the compact, although uniformities appear to be evenly dispersed throughout the analysed volume. The voids produced during fabrication were on average plate-like in nature with their major axis oriented perpendicular to the compaction direction of the compact. Finally, the microstructure, mainly the large preferentially oriented voids, may cause a small degree of anisotropy in the thermal diffusivity within the compact. α∥/α⊥, the ratio of thermal diffusivities parallel to and perpendicular to the compaction direction are expected to be no less than 0.95 with an upper bound of 1.

821 超音波伝播解析によるボイドやはく離を有するCFRP複合材料の動的力学挙動の評価(GS4-4 材料力学・計算力学)

For the characterization and defect detection of carbon fiber reinforced composite materials, Ultrasonic Testing is one of several commonly used nondestructive examination techniques for its sensitivity and accuracy. However, owing to the complicated interactions among fibers, delamination, randomly distributed voids, and the ultrasonic wave propagation, the detailed effect mechanisms of the above internal damage on wave propagation and material properties haven't been clarified. Thus, our work is dedicated to the detailed effect mechanism of void and delamination on ultrasonic wave propagation and the dynamic mechanical properties, for giving guidance on the development of high-precision ultrasonic testing technology.

On-Line Monitoring of Environment-Assisted Cracking in Nuclear Piping Using Array Probe Direct Current Potential Drop

A direct current potential drop method utilizing array probes with measurement ends maintaining an equalized potential designated as equi-potential switching array probe direct current potential drop (ESAP-DCPD) technique has been developed earlier at Seoul National University. This paper validates ESAP-DCPD technique by showing consistency among experimental measurements, analytical solution and numerical predictions using finite element analysis (FEA) of electric field changes with crack growth in metals. In order to examine its viability as an on-line monitoring of environment assisted crack growth at the inner surface of piping welds, artificial inner surface cracks were introduced in a full-scale weldment mockup pipe and stainless steel metal mockup pipe. The weldment was joined by low alloy steel and stainless steel pipes. The pipes were monitored by using ESAP-DCPD in laboratory environments. Optimization of electrical wiring configuration has produced results with significantly reduced noise for adequately long period of time. Then optimized experimental results were compared with the FEA prediction results for the mockup to show a good agreement. Also a round-robin measurement has been made at three laboratories. It has been found that the developed ESAP-DCPD can detect circumferential cracks with a depth of 40 % of wall thickness in stainless steel with a good detectability for further growth behaviors. For axial cracks, however, the measurements showed poor detectability. Hence the developed ESAP-DCPD system can be used to monitor large circumferential cracks that existing non-destructive examination techniques often fail to detect until leakage takes place.

NON-DESTRUCTIVE EXAMINATION USING NEUTRONS: A NUCLEAR WASTE AND ORPHANED SOURCE CHARACTERIZATION CASE STUDY APPLICABLE TO NUCLEAR FORENSICS

Found unknown radioactive material is often contained in a package so the chemical and physical form of the material itself is unknown, and the detail of the packaging is likewise unknown. Together, these present a significant risk on how to handle the package for destructive examination of its contents. Whether of nefarious origin or the result of less stringent practices of yesteryear the material needs to be properly identified and characterized for appropriate disposition. Results of neutron imaging, neutron diffraction, and delayed neutron analysis as applied to an examination of sealed capsules containing unknown radioactive materials are presented. The results demonstrate that neutron-based non-destructive examination techniques can be employed for inspecting encapsulated radioactive samples to identify the materials, to elucidate the internal physical structure of the radioactive material and encapsulation, and to estimate the mass of fissile and fissionable materials within. This characterization of orphaned radioactive special nuclear material illustrates the potential for these techniques in nuclear forensics investigations.