Power converter devices require a high level of quality because they have a high direct connection with vehicle operation. Therefore, structural bonding was carried out by friction stir welding with excellent mechanical properties. Friction stir welding can cause structural deflection depending on the load of the welding tool, so it is important to control this for high quality flatness. In this study, pre-welding was performed before welding to minimize deflection generated during welding. And deflection reduction data according to the location of pre-welding were analyzed through dynamic analysis. As a result, based on computerized data rather than experimental data an optimized position of pre-welding was secured to minimize the deflection that occurs during friction stir welding. Through this, a process guide that enables high quality structural bonding was presented.

2015년부터 2022년도까지 6개목(딱정벌레목, 노린재목, 나비목, 벌목, 파리목, 총채벌레목) 곤충들에 대해서 식물검역현장 검출실적과 국내 보고된 미기록종을 분석하였다. 해당기간 동안 국경검역에서 6개목 곤충은 총 45,084건이 검출되었다. 같은 기간 국내에서는 총 545종이 미기록종 으로 보고되었으며, 이중 9종은 국경검역에서도 검출된 것으로 확인되었다. 검역현장에서는 딱정벌레목, 총채벌레목, 노린재목이 높은 검출률을 보 였으며, 국내 미기록종 중에서는 벌목이 176종으로 가장 많이 보고되었다. 본 연구를 통해 침입압력(국경검역 검출)과 실제 침입(국내 미기록종 발 견) 사이에 비동시성이 확인되었다. 향후 보다 장기적인 분석이 필요할 뿐만 아니라 지속적인 식물검역시스템 개선이 필요할 것으로 판단된다.

Effective containment and disposal of high-level radioactive waste is critical to ensure long-term environmental and human safety. Especially bentonite, which is widely used as a buffer material due to its favorable characteristics such as swelling ability and low permeability, plays an important role in preventing the migration of radioactive waste into the surrounding environment. However, the long-term performance of bentonite buffer remains an area of ongoing investigation, with particular attention focused on erosion mechanisms induced by swelling and groundwater flow. The erosion of the bentonite buffer can significantly impact the integrity of buffer and lead to the formation of colloids, which could potentially facilitate the transport of radionuclides through groundwater. Therefore, quantification of bentonite buffer erosion based on an understanding of the underlying mechanisms and factors that influence bentonite buffer erosion, is essential for the safety assessment of high-level radioactive waste repositories. In this study, we aimed to develop a bentonite buffer erosion model using the Adaptive Processbased total system performance assessment framework for a geological disposal system (APro) proposed by the Korea Atomic Energy Research Institute (KAERI). The impact of bentonite erosion on performance assessment can be broadly divided into bentonite property degradation by the penetration of the bentonite buffer into rock fractures and the formation of pseudocolloids. To simulate this phenomenon, Two-region model based on a dynamic bentonite diffusion model is adopted, which can quantify the extent of bentonite intrusion and loss by erosion. Using this Tworegion model, a numerical model was developed to simulate the degradation of bentonite properties based on the amount of bentonite intrusion, as well as to simulate the migration of pseudocolloids in the near-field by deriving the amount of pseudocolloid production based on the loss of bentonite and the sorption rate of radionuclides. To check the applicability of the developed numerical model, preliminary analysis was performed for the effect of bentonite erosion in terms of process-based performance assessment. It is anticipated that this comprehensive model developed in this study will contribute to the accurate and reliable assessment of the long-term performance and safety of high-level radioactive waste repositories.

Bentonite is a widely used buffer material in high-level radioactive waste repositories due to its favorable properties, including its ability to swell and low permeability. Bentonite buffers play an important role in safe disposal by providing a low permeability barrier and preventing radionuclides migration into the surrounding rock. However, the long-term performance of the bentonite buffer is still an area of research, and one of the main concerns is the erosion of the buffer due to swelling and groundwater flow. Erosion of the bentonite buffer can have a significant impact on repository safety by reducing the integrity of the buffer and forming colloids that can transport radionuclides through groundwater, potentially increasing the risk of radionuclide migration. Therefore, understanding the mechanisms and factors that influence the erosion of the bentonite buffer is critical to the safety assessment of high-level radioactive waste repositories. In this study, we attempted to develop the bentonite buffer erosion model using Adaptive Processbased total system performance assessment framework for a geological disposal system (APro) proposed by the Korea Atomic Energy Research Institute (KAERI). First, the erosion phenomenon was divided into two stages: bentonite buffer penetration into rock fractures and colloid formation. As an initial step in the development of the buffer erosion model, a bentonite buffer intrusion into the fracture and consequent degradation of buffer property were considered. For this purpose, a tworegion model based on the dynamic bentonite diffusion model was adopted which is one of the methods for simulating bentonite buffer intrusion. And, it was assumed that the buffer properties, such as density, porosity and permeability, thermal conductivity, modulus of elasticity, and mechanical strength, are degraded as the buffer erodes. The bentonite buffer degradation model developed in this study will serve as a foundation for the comprehensive buffer erosion model, in conjunction with the colloidal formation model in the future.

Excavation Damaged Zone (EDZ) is created by the excavation of deposition holes and disposal tunnels at high-level radioactive waste repository that causes macro- and micro-fracturing in the surrounding rock. Since EDZ can significantly increase the hydraulic transmissivity in the rock and act as a major pathway of leaked radionuclides, consideration of EDZ in terms of safety assessment is very important. Moreover, long-term stress changes such as stress redistribution due to excavation of nearby deposition holes and disposal tunnels, thermal stress due to temperature rise, effective stress change due to pore pressure change, and swelling pressure of bentonite buffer can increase EDZ size and change in thermal-hydraulic-mechanical properties, and consequently, it can affect the transport of radionuclides. Therefore, in order to analyze the effect of long-term evolution of EDZ on radionuclide transport, it is essential to conduct numerical analysis considering the coupled Thermal-Hydraulic- Mechanical (THM) behavior in EDZ. In order to simulate the behavior of EDZ, coupled THM model was developed using the Adaptive Process-based total system performance assessment framework for a geological disposal system (APro) proposed by the Korea Atomic Energy Research Institute (KAERI). The concept of damage was introduced to demonstrate the jointed rock as a continuous medium. Among several damage models, Mazars damage model was applied in this study. Mazars damage model is the most well-known model for concrete which has similar behavior with rock as brittle material, and the input data of the model can be easily obtained through laboratory testing. If damage occurs due to the influence of thermal-hydraulic-mechanical coupled behavior at the bedrock, the properties change according to the degree of damage, and as a result, the migration of the radionuclide is affected. Based on this conceptual model, radionuclide transport model in the near field considering the long-term evolution of EDZ was developed. To investigate the effect of EDZ in terms of process-based performance assessment, the modeling results with and without EDZ were compared. Finally, by simulating the coupled THM behavior of EDZ with damage model, the effect of long-term evolution of EDZ on radionuclide transport was investigated.

In recent years, the importance of the thermo-hydraulic-mechanical-chemical coupled processes is increasing in the performance assessment (PA) of the high-level radioactive waste repository. In the case of mechanical behavior, it is very important because it can affect fluid flow and radionuclide transport by changing the porosity and permeability of the medium. In particular, Excavation Damaged Zone (EDZ) should be considered essential in PA because the migration of radionuclide is affected by the enhanced hydraulic transmissivity and altered geomechanical behavior of EDZ. Furthermore, due to various thermo-hydraulic behaviors such as decay heat generated from radioactive waste, pore water pressure increase, and swelling pressure of bentonite buffer material, mechanical evolution is occurred which may change the size and physical properties of EDZ. Therefore, to solve this problem, analysis of coupled thermal-hydraulic-mechanical (THM) processes with the effect of long-term evolution of EDZ due to the mechanical behavior should be accompanied. In this study, numerical model for the long-term evolution due to mechanical behavior considering EDZ using the Adaptive Process-based total system performance analysis framework for a geological disposal system (APro) proposed by the Korea Atomic Energy Research Institute (KAERI). In the case of EDZ, the concept of Mazars’ damage evolution model was applied to simulate the behavior using the continuum model, and the change in hydraulic properties according to the degree of damage was considered. To investigate the importance of mechanical behavior in PA, the results were compared by performing numerical analysis according to the presence or absence of mechanical analysis. Finally, numerical analysis considering the mechanical evolution of EDZ was conducted using the model developed in this study to investigate the effect of EDZ.

Riptortus pedestris is a major agricultural pest in Korea. To manage this pest, it is necessary to understand the complete life history of R. pedestris. However, most studies have focused on the summer period when the pest attacks crops. Therefore, we conducted laboratory and field experiment to identify overwintering behavior of adult R. pedestris. First, we conducted two laboratory experiments to examine overwintering habitat preferences and spatial distribution of R. pedestris in the habitat. Second, we conducted field survey to characterize overwintering sites of R. pedestris in diverse landscapes. In the laboratory conditions, R. pedestris almost exclusively showed overwintering behavior in the leaf litter arena (63%) among the structures tested (rocks: 3%; rotten wood: 0%). And spatial distribution of R. pedestris showed solitary behavior in leaf litters. In the field, we located 12 individuals of overwintering adults from the urban areas, whereas no individuals were found from the high-elevation mountains and agricultural landscapes. Our results suggest that R. pedestris mainly use leaf litter as an overwintering structure, with solitary behavior, and low-elevation forested areas near urban landscapes seem to be more preferred overwintering sites.

Whiteflies (Hemiptera: Aleyrodidae) and thrips (Thysanoptera: Thripidae) are major pests on greenhouse crops including sweet pepper (Capsicum annuum L.) in South Korea. To manage this pest complex effectively, it is fundamental to understand population dynamics and spatial distributions of the pests. In this study, we conducted visual counting and used yellow sticky traps to monitor whitefly and thrips populations in sweet pepper greenhouse (6 × 28 m). The survey was conducted every two weeks over two months. A total of 84 traps were set up at 20cm from the plant top canopy and spaced 1m apart from each other. Leaves were selected randomly from the middle plant canopy for visual counting at the same sampling locations. The trap data indicate that the numbers of whiteflies and thrips increased from 5.50 ± 0.34 to 168.51 ± 14.95 and from 52.40 ± 1.67 to 158.42 ± 7.44 (mean ± SE) per trap, respectively, over the two-month observation period. In general, the spatial distributions of these pests aggregated near the greenhouse entrance with significant positive correlation between the densities of the two species (r = 0.74, P = 0.02). However, the results of visual counting were completely different; either species was rarely found on leaves, even when the trap catches were relatively high at the same locations. That is, there was no correlation between visual counting and sticky trap data sets. The current study will serve as a fundamental step to develop reliable and effective management programs for greenhouse sweet pepper.

Sweet pepper (Capsicum annuum L.) is one of the leading export greenhouse crops in South Korea. Sweetpotato whitefly, Bemisia tabaci Gennadius is one of the major pests on greenhouse pepper. This pest is conventionally managed by synthetic insecticide application, however this management tactic causes the overuse of toxic compounds and the resistance of whiteflies to insecticides. Therefore, the development of environment-friendly natural insecticides is vitally important. In this study, we evaluated the efficacy of three newly-screened insecticidal compounds for B. tabaci (Biotype Q) in laboratory. The insecticidal effects of the compounds were assessed with adult B. tabaci using leaf disc arena established in petri dish. Among the three compounds tested, JS408, a plant extract from Perilla sp., showed significant insecticidal effects on B. tabaci in one hour causing 90% mortality. However, JA408 caused phytotoxicity on sweet pepper leaf resulting in browning dead spots. The new plant-extract JA408 has promising potential as natural insecticidal compound for B. tabaci, but further study must resolve the phytotoxicity issue. Moreover, insecticidal effect should be evaluated under field conditions.