Korea Institute of Nuclear Safety

Theophylline, a methylxanthine-class bronchodilator that has anti-inflammatory properties, is clinically used to manage chronic respiratory disorders such as asthma and chronic obstructive pulmonary disease. Although theophylline demonstrates therapeutic efficacy, it has a narrow therapeutic index and central nervous system (CNS) activity, which requires a detailed safety assessment. This study investigated the acute neurobehavioral and thermophysiological effects of orally administered theophylline in male Institute of Cancer Research (ICR) mice using the modified Irwin test. Single doses of 10, 30, or 100 mg/kg of theophylline were administered, followed by structured behavioral observations at 0, 1, 2, 4, 6, and 24 h post-dosing. Administration at concentrations of 30 and 100 mg/kg induced transient hyperthermia, increased spontaneous locomotion, and reversible motor coordination deficits between 1 and 6 h, with full recovery by 24 h. Tail elevation was observed only at concentrations of 30 mg/kg, whereas partial eyelid closure occurred exclusively in mice receiving 100 mg/kg administered doses. However, doses of 10 mg/kg did not produce measurable changes in any of these parameters. No notable alterations were detected in the abdominal tone, tremors, convulsions, respiration, righting reflex, salivation, lacrimation, skin color, or exophthalmos, thereby indicating the absence of systemic or generalized CNS toxicity. The modified Irwin test captured the subtle, regionally selective neurofunctional responses induced by theophylline, thus emphasizing its relevance in CNS safety pharmacology and supporting continued mechanistic investigations under clinically relevant exposure conditions.

An Ultrasonic Test (UT), a type of non-destructive test, is used to inspect the manufacturing integrity of carbon spar-caps of wind blades. When performing a UT, an intermediate medium is used to improve the signal detection ability between the inspection target and the probe. However, if the intermediate-medium residue is not removed, it acts as a contaminant in the interface between the spar-cap and the blade skin. This has a negative effect on the adhesion characteristics. A quantitative method is required for removing the intermediate medium and peel ply after the UT. After the UT, the interfacial characteristics of the spar-cap surface are examined according to the method of removing the intermediate medium in this study. The static contact angle and the work of adhesion (Wa) were measured according to various surface treatment conditions. In addition, shear strength of the Carbon Fiber-Reinforced Plastic (CFRP) spar-cap was evaluated by the lap shear test. An optimized method of peel-ply removal combined with an intermediate medium was found in this study. An optimal guideline for intermediate-medium treatment could be proposed when evaluating the manufacturing integrity of real wind blade spar-caps using UT.

In the present study, a comprehensive dataset of dose coefficients for idealized external electron exposures has been established using the newly released ICRP-156 pediatric mesh-type reference computational phantoms (MRCPs) in conjunction with the Geant4 Monte Carlo radiation transport code. The dataset comprises organ/tissue-averaged absorbed dose coefficients for the 29 target organs and tissues which contribute to the effective dose, as well as effective dose coefficients, spanning three idealized, unidirectional, whole body irradiation geometries—antero-posterior (AP), postero-anterior (PA), and isotropic (ISO)—across 49 discrete electron energies from 10 keV to 10 GeV. Comparisons with the ICRP-145 adult MRCPs revealed significant age-dependent variations, with effective dose coefficients differing by up to ∼38 times (5 years, PA, 50 keV), primarily due to variations in organ/tissue depths across different ages. Further comparisons with the ICRP-143 pediatric voxel-type reference computational phantoms (VRCPs) showed substantial differences below 10 MeV, with effective dose coefficients differing by up to four orders of magnitude, largely attributable to the inclusion of the thin skin target layer in the pediatric MRCPs. The findings of the present study are expected to serve as a valuable resource for optimizing radiological protection strategies for the pediatric population.

The Optical Fiber Radiation Probe System (OFPS), which utilizes optical fiber-based scintillation detectors, has been employed by inspectors from the International Atomic Energy Agency (IAEA) and South Korea to verify spent fuel bundles from CANDU-type heavy water reactors. To address challenges identified in previous studies, the OFPS is currently undergoing enhancements to improve its performance. As part of these upgrades, two novel optical fiber-based scintillation detectors have been designed and manufactured. A comprehensive field test was conducted at the Wolseong Nuclear Power Plant, a CANDU-type facility in South Korea, to evaluate and compare the performance of the existing detector with the newly developed detectors. The objective of this study is to assess the performance of optical fiber-based scintillation detectors in terms of Peak-to-Valley Ratio (PVR) and their ability to distinguish between stacked spent fuel bundles. Three different radiation detectors — one existing OFPS detector and two newly developed detectors for the Improved Optical Fiber-based Verification System (IOVES) — were evaluated during the field tests. Experimental results indicated that although the difference in PVR was modest, the IOVES detector with an optical fiber core diameter of 1.0 mm and a scintillator size of 4.0 mm × 4.0 mm × 10.0 mm demonstrated the highest PVR. However,thedetector exhibited signal saturation due to high background radiation when measuring highly radioactive spent fuel. Conversely, the IOVES detector featuring a 0.6 mm optical fiber diameter and a 2.5 mm × 2.5 mm × 10 mm p-terphenyl organic scintillator showed a marginally lower PVR value but successfully distinguished layered spent fuel bundles regardless of the spent fuel radioactivity level or cooling period. Actual spent fuel storage pools contain both extremely low-radioactivity spent fuel with extended cooling periods and highly radioactive recently discharged spent fuel. Considering this realistic operational scenario, the optical fiber-based scintillation detector with a 0.6 mm optical fiber core diameter and a 2.5 mm × 2.5 mm × 10 mm p-terphenyl scintillator demonstrated optimal performance among the three detectors tested. Consequently,theoptical fiber-based radiation detector is expected to enhance the efficiency and effectiveness of inspection activities by the IAEA and national authorities because it can reliably measure spent fuel bundles regardless of their cooling periods.

Using used serviceable material (USM), recycled and upcycled, for aircraft is environmentally and financially beneficial in helping the aviation industry achieve sustainability. This study aims to identify determinants of aircraft USM value and assess their significance using the Fuzzy Analytic Hierarchy Process (FAHP) to gain insights for making the USM market more active. Sixteen factors in four categories are selected based on literature and focus group interviews. A survey to analyze factor priority is conducted with 118 industry experts. The results show that maintenance requirements, airworthiness directive status, and maintenance status from the technical category are the most critical determinants of aircraft USM value, followed by traceability, former operator, and former aviation authority from the operational category and new part value. The technical category corresponds to “must-be” traits in the Kano model, requiring compliance by sellers, whereas new part value information can help buyers’ decisions. The implementation of an internationally agreed mutual accreditation system for approved maintenance organizations and a standard for aircraft dismantling is proposed to improve technical and operational determinants to achieve fewer uncertainties in USM valuation. This study aims to offer a new guideline for evaluating USM value to market participants. Price modeling of USM is left for future studies.

Near Galpyeong Reservoir in northern Cheongsong County, mid-eastern Korean Peninsula, a rhyolitic stock with an elliptical shape is exposed, measuring about 2 km by 1 km. Surrounding this stock, rhyolitic dykes radially intrude the Cretaceous sedimentary rocks within a 4 to 5 km range. These dykes are mainly grayish-blue or brown, with occasional white dykes. They contain well-developed spherulitic textures, with spherulites up to 1 meter or more in diameter. Due to their diverse floral-like shapes, they have been traditionally called "flower stones" and are recognized as a key geosite of the Cheongsong Global Geopark.The rhyolitic dykes, with widths of 0.5 to 3 m, display non-linear, curved paths. Brown dykes crosscut grayish-blue ones, and larger spherulites occur in dyke cores, while smaller ones are located at the margins. Flow banding, induced by shearing, is more prominent at the margins and in the brown dykes. Elongated cavities are frequently observed along flow bands in brown dykes, but these bands do not penetrate the spherulites. The spherulites in brown dykes are generally larger and often encased in mafic outer crusts, facilitating easy separation from the host rock.The chemical composition of the rhyolitic dykes corresponds to the subalkaline series of rhyolites. Spherulites show relatively lower SiO₂ content than the matrix, but in the spider diagram, there are minimal compositional differences between the spherulites and the matrix.Spherulites primarily formed through a combination of radial and spherical quartz growth. Their nucleation centers include quartz, orthoclase, or flow structures, though in some cases, no nucleus is identifiable. Some spherulites exist as individual units, while others are aggregates of smaller spherulites forming larger ones. In the brown dykes, most large spherical spherulites are clusters of numerous smaller ones.Chemical composition analysis from the center of the spherulites to the matrix indicates SiO₂ and Na₂O contents are highest in the spherulite interiors, decreasing sharply in the nearby matrix and stabilizing at low levels at greater distances. In contrast, Al₂O₃, K, and FeO contents are lowest in the spherulite interiors, peaking at the surfaces, and decreasing gradually to relatively high levels further away.The zircon saturation geothermometer suggests that in grayish-blue dykes, spherulites and matrix formed at nearly the same temperature, while in brown dykes, spherulites formed at higher temperatures than the matrix.These findings indicate that the margins of a rhyolitic magma chamber cooled rapidly, enabling spherulites to form under relatively high internal temperatures. The initial dykes likely formed without incorporating chamber spherulites. In a subsequent phase, dykes transported pre-existing spherulites, during which flow structures developed around the already solid spherulites.

The increasing integration of digital technologies within nuclear power plants has heightened their susceptibility to cyber threats, underscoring the need for advanced research frameworks dedicated to cybersecurity. This research introduces HINT-Sec, a high-fidelity hardware-in-the-loop testbed meticulously designed for cybersecurity research in nuclear power plants. HINT-Sec integrates a verified NPP simulator with both safety-grade and non-safety-grade programmable logic controllers, as well as distributed control systems, facilitating the realistic simulation of cyber-attacks and their consequent impacts on nuclear operations. Through comprehensive performance testing and scenario validation, the capability of HINT-Sec to accurately replicate the behavior of the APR1400 reactor under both normal and abnormal conditions is demonstrated. This capability provides a robust platform for the evaluation and development of cybersecurity measures within NPP environments. The design and implementation approach of the HINT-Sec testbed represents a significant contribution to the field of nuclear cybersecurity, ensuring that future research will be equipped to address the intricate challenges posed by cyber threats in critical infrastructure.