The occurrence of shear failure in a rock mass, resulting from the sliding of joint surfaces, is primarily influenced by the surface roughness and contact area of these joints. Furthermore, since joints serve as crucial conduits for the movement of water, oil, gas, and thermal energy, the aperture and geometric complexity of these joints have a significant impact on the hydraulic properties of the rock mass. This renders them critical factors in related industries. Therefore, to gain insights into the mechanical and hydraulic behavior of a rock mass, it is essential to identify the key morphological characteristics of the joints mentioned above. In this study, we quantified the morphological characteristics of tensile fractures in granitic rocks using X-ray CT imaging. To accomplish this, we prepared a cylindrical sample of Hwang-Deung granite and conducted splitting tests to artificially create tensile fractures that closely resemble rough joint surfaces. Subsequently, we obtained 2D sliced X-ray CT images of the fractured sample with a pixel resolution of approximately 0.06 mm. By analyzing the differences in CT numbers of the rock components (e.g., fractures, voids, and rock matrix), we isolated and reconstructed the geometric information of the tensile fracture in three dimensions. Finally, we derived morphological characteristics, including surface roughness, contact area, aperture, and fracture volume, from the reconstructed fracture.

Engineered Barrier Systems (EBS) are a key element of deep geological repositories (DGR) and play an important role in safely isolating radioactive materials from the ecosystem. In the environment of a DGR, gases can be generated due to several factors, including canister corrosion. If the gas production rate exceeds the diffusion rate, pore pressures may increase, potentially inducing structural deterioration that impairs the function of the buffer material. Therefore, understanding the hydraulic-mechanical behavior of EBS due to gas generation is essential for evaluating the longterm stability of DGR. This study employed X-ray computed tomography (CT) technology to observe cracks created inside the buffer material after laboratory-scale gas injection experiments. After CT scanning, we identified cracks more clearly using an image analysis method based on machine learning techniques, enabling us to examine internal crack patterns caused by gas injection. In the samples observed in this study, no cracks were observed penetrating the entire buffer block, and it was confirmed that most cracks were created through the radial surface of the block. This is similar to the results observed in the LASGIT field experiment in which the paths of the gas migration were observed through the interface between the container and the buffer material. This study confirmed the applicability of high-resolution X-ray CT imaging and image analysis techniques for qualitative analysis of internal crack patterns and cracks generated by gas breakthrough phenomena. This is expected to be used as basic data and crack analysis techniques in future research to understand gas migration in the buffer material.

Crystallographic properties of Ni-based alloys such as alloys 600, 617, and Hastelloy N, which are a candidate to be used as structural materials in Molten Salt Reactor (MSR), were studied in the temperature range of 25-1,000°C using high-temperature X-ray diffraction (HT-XRD) under an Ar atmosphere. We found that face-centered cubic Ni crystal structure at room temperature was started to be changed over 600°C in all Ni-based samples. However, the appearance of changing diffraction patterns over 600°C was different for all samples. In addition, we observed the increase in the lattice constant along the a-axis upon heating in all specimens, determined by Pawley refinement of HTXRD data.

According to ISO 4037, the thickness of the inherent filtration for the radiation qualities L-40 to L- 240, N-40 to N-400, W-60 to W-300 and H-80 to H-400 shall be equivalent to 4 mm Al for matched reference radiation fields or adjusted as far as possible to 4 mm Al for characterized reference radiation fields. And for matched reference fields, the tube window must be made of beryllium and its thickness should not exceed 10 mm. In the case of characterized reference fields, the thickness of the beryllium window should not exceed 10 mm, but it is acceptable to use an aluminum window with a maximum thickness of 1.5 mm. 320 KV X-ray tube installed at KHNP-CRI has been designed to equipped with a 3 mm Be for tube window and an additional 4 mm Al to obtain a total inherent filtration equivalent to that of 4 mm Al. In the previous study, the inherent filtration of 320 kV X-ray tube at KHNP-CRI has been verified by MCNP simulation. However, the ISO standards suggest a method for determining the thickness of the inherent filtration by half-value layer (HVL) measurement and spectrometry. In this regard, the inherent filtration was reassessed using HVL measurement. To determine the inherent filtration, 1st HVL of the beam generated by the tube at a tube potential 60 kV was measured. The measurements were conducted with a calibrated spherical ionization chamber (model A3, Exradine) placed at a distance of 1 m from the target, at the center of the radiation field size. The X-ray tube current was set to 2 mA. The thickness of aluminum absorbers was gradually adjusted in subsequent measurements until approached the 1st HVL. 1st HVL were estimated using the linear regression equation computed with the current values for the thickness of the absorbers. As a results, the thickness of the 1st HVL was estimated as 2.845 mm Al. According to the correlation between the inherent filtration and 1st HVL suggested in ISO standard, the value of the inherent filtration was deduced as 4.25 mm Al that is rounded to the nearest 0.05 mm by interpolation. Further studies on the effects of the inherent filtration thickness determined in this study will be conducted.

Since 2018, Central Research Institute of Korea Hydro & Nuclear Power (KHNP–CRI) has been operating an X-ray irradiation system with a maximum voltage of 160 kV and 320 kV X-ray tube to test personal dosimeters in accordance with ANSI N13.11-2009 “Personnel Dosimetry Performance- Criteria for Testing”. This standard requires that dosimeters for the photon category testing be irradiated with the X-ray beams appropriate to the ISO beam quality requirements. KHNP-CRI has implemented the fourteen X-ray reference radiation beams in compliance with ISO-4037-1, 2, and 3. When installing the X-ray irradiation system, KHNP-CRI evaluated the uncertainties of dose conversion coefficients for deep and shallow doses, based on “Catalogue of X-ray spectra and their characteristic data – ISO and DIN radiation qualities, therapy and diagnostic radiation qualities, unfiltered X-ray spectra” published by Physikalisch Technische Bundesanstalt (PTB). A CdTe detector (X-123, AMPTEK) with disk type collimators made of tungsten was used to acquire X-ray spectra. The detector was located at 1 m from the center of the target material in the Xray tubes. Six uncertainty factors for the dose conversion coefficients for the fourteen X-ray beams were chosen as follows; the minimum and maximum cut-off energies Emin and Emax, the air density (ρ), the accuracy of the high-voltage of the X-ray tube, statistics of the pulse height spectra and the unfolding method. For example, uncertainty of each quantity for a HK30 beam was calculated to be 0.3%, 2.32%, 0.19%, 1.25%, and 0.13%, and 0.18%, respectively. The combined standard uncertainty for the deep dose conversion coefficient of the HK30 beam was calculated to be 2.67%. The coverage factor corresponding to a 95 percent confidence interval was obtained as k = 1.8 using a Monte Carlo method, which is slightly lower the coverage factor of k = 1.95 for a Gaussian distribution. This seems to result from that two dominant uncertainties, the unfolding uncertainty and minimum cut-off energy uncertainty, follow a rectangular distribution.

Metakaolin-based geopolymers have shown promise as suitable candidates for 14C immobilization and final disposal. It has been shown that the physicochemical properties of metakaolin wasteforms meet, and often far exceeding, the strict compression strength and leaching acceptance criteria of the South Korea radioactive waste disposal site. However, it is not possible to analyze and characterize the internal structure of the geopolymer wasteform by conventional characterization techniques such as microscopy without destruction of the wasteform; an impractical solution for inspecting wasteforms destined for final disposal. Internal inspection is important for ensuring wastes are homogenously mixed throughout the wasteform and that the wasteform itself does not pose any significant defects that may have formed either during formulation and curing or as a result of testing prior to final disposal. X-ray Computed Tomography (XCT) enables Non-Destructive Evaluation (NDE) of objects, such as final wasteforms, allowing for both their internal and external, characterization without destruction. However, for accurate quantification of an objects dimensions the spatial resolution (length and volume measures) must be know to a high degree of precision and accuracy. This often requires extensive knowledge of the equipment being used, its precise set-up, maintenance and calibration, as well as expert operation to yield the best results. A spatial resolution target consists of manufactured defects of uniformed dimensions and geometries which can be measured to a high degree of accuracy. Implementing the use of a spatial resolution target, the dimensions of which are known and certified independently, would allow for rapid dimensional calibration of XCT systems for the purpose of object metrology. However, for a spatial resolution target to be practical it should be made of the same material as the intended specimen, or at least exhibit comparable X-ray attenuation. In this study, attempts have been made to manufacture spatial resolution targets using geopolymer, silica glass, and alumina rods, as well as 3D printed materials with varying degrees of success. The metakaolin was activated by an alkaline activator KOH to from a geopolymer paste that was moulded into a cylinder (Diameter approx. 25 mm). The solidified geopolymer cylinder as well as both the silica glass rod and alumina rod (Diameter approx. 25 mm) we cut to approximately 4 mm ± 0.5 mm height with additional end caps cut measuring 17.5 mm ± 2.5 mm height. All parts were then polished to a high finish and visually inspected for their suitability as spatial resolution targets.

The most comprehensive and particularly reliable method for non-destructively measuring the residual stress of the surface layer of metals is the sin method. When X-rays were used the relationship of sin measured on the surface layer of the processing metal did not show linearity when the sin method was used. In this case, since the effective penetration depth changes according to the changing direction of the incident X-ray,  becomes a sin function. Since  cannot be used as a constant, the relationship in sin cannot be linear. Therefore, in this paper, the orthogonal function method according to Warren’s diffraction theory and the basic profile of normal distribution were synthesized, and the X-ray diffraction profile was calculated and reviewed when there was a linear strain (stress) gradient on the surface. When there is a strain gradient, the X-ray diffraction profile becomes asymmetric, and as a result, the peak position, the position of half-maximum, and the centroid position show different values. The difference between the peak position and the centroid position appeared more clearly as the strain (stress) gradient became larger, and the basic profile width was smaller. The weighted average strain enables stress analysis when there is a strain (stress) gradient, based on the strain value corresponding to the centroid position of the diffracted X-rays. At the 1/5 max height of X-ray diffraction, the position where the diffracted X-ray is divided into two by drawing a straight line parallel to the background, corresponds approximately to the centroid position.

Domestic nuclear facilities establish a physical protection system to respond to illegal transfer of nuclear materials and sabotage to nuclear materials and nuclear facilities, and operate a security search system in order to prevent the entry of controlled items into the facility. X-ray security search is also the most widely used for such security search. Since 2018, Korea Institute of Nuclear Nonproliferation and Control (KINAC) has developed the “X-ray security screening Web-Based Training Program (XWBT)” and has been using it in the physical protection education. The XWBT contains about 700 X-ray images of the item, and can learn X-ray images by type or package of the item. In addition, trainees can practice reading the X-ray image of the item or package, looking for controlled items, and determining whether the item could be passed or opened. However, there is a limit to Web-Based X-ray training program alone. This is because even if the same item is contained in the same bag, the X-ray image could be varied depending on the direction, angle, and other items in the package. Therefore, in addition to XWBT, X-ray reading practice education for actual luggage should be conducted in parallel. In addition, trainees should be familiar with various images through repetitive X-ray reading practice training so that they should be able to intuitively read X-ray images and find controlled items. Therefore, securing educational time is essential to produce skilled trainees. Korea Aviation Security Academy (KASA), which produces professional security inspectors, has established and operated a “Security search education filed for actual luggage” where trainees can pack their own bags, read X-ray images, and practice whether there are controlled items packed. In addition, KASA provides 40-hour training for security search personnel, which focuses on improving the practical skills that security search personnel must have. This study describes the current status of “X-ray Security Search” of Physical Protection Education for security personnel and presents course improvements through the case of KASA.

Using I-band images of 35 nearby (z < 0.1) type 1 active galactic nuclei (AGNs) obtained with Hubble Space Telescope, selected from the 70-month Swift-BAT X-ray source catalog, we investigate the photometric properties of the host galaxies. With a careful treatment of the point-spread function (PSF) model and imaging decomposition, we robustly measure the I-band brightness and the effective radius of bulges in our sample. Along with black hole (BH) mass estimates from single-epoch spectroscopic data, we present the relation between BH mass and I-band bulge luminosity (MBH–MI,bul relation) of our sample AGNs. We find that our sample lies offset from the MBH–MI,bul relation of inactive galaxies by 0.4 dex, i.e., at a given bulge luminosity, the BH mass of our sample is systematically smaller than that of inactive galaxies. We also demonstrate that the zero point offset in the MBH–MI,bul relation with respect to inactive galaxies is correlated with the Eddington ratio. Based on the Kormendy relation, we find that the mean surface brightness of ellipticals and classical bulges in our sample is comparable to that of normal galaxies, revealing that bulge brightness is not enhanced in our sample. As a result, we conclude that the deviation in the MBH–MI,bul relation from inactive galaxies is possibly because the scaling factor in the virial BH mass estimator depends on the Eddington ratio.

Lately, Raman spectroscopy has become powerful tool for quality assessment of graphene analogues with identification of intensity ratio of Raman active D-band and G-band ( ID/IG ratio) as a vital parameter for quantification of defects. However, during chemical reduction of graphitic oxide (GrO) to reduced GrO (RGrO), the increased ID/ IG ratio is often wrongly recognized as defect augmentation, with “formation of more numerous yet smaller size sp2 domains” as its explanation. Herein, by giving due attention to normalized peak height, full-width half-maxima and integrated peak area of Raman D- and G-bands, and compliment the findings by XRD data, we have shown that in-plane size of sp2 domains actually increases upon chemical reduction. Particularly, contrary to increased ID/ IG ratio, the calculated decrease in integrated peak area ratio ( AD/AG ratio) in conjunction with narrowing of D-band and broadening of G-band, evinced the decrease in in-plane defects. Finally, as duly supported by reduction induced broadening of interlayer-spacing characteristic XRD peak and narrowing of ~ 43° centered XRD hump, we have also shown that the sp2 domains actually expands in size and the observed increase in ID/ IG ratio is indeed due to increase in across-plane defects, formed via along-the-layer slicing of graphitic domains.

Metal three-dimensional (3D) printing is an important emerging processing method in powder metallurgy. There are many successful applications of additive manufacturing. However, processing parameters such as laser power and scan speed must be manually optimized despite the development of artificial intelligence. Automatic calibration using information in an additive manufacturing database is desirable. In this study, 15 commercial pure titanium samples are processed under different conditions, and the 3D pore structures are characterized by X-ray tomography. These samples are easily classified into three categories, unmelted, well melted, or overmelted, depending on the laser energy density. Using more than 10,000 projected images for each category, convolutional neural networks are applied, and almost perfect classification of these samples is obtained. This result demonstrates that machine learning methods based on X-ray tomography can be helpful to automatically identify more suitable processing parameters.