Low- and intermediate-level radioactive wastes have been disposed of in the first-phase deep underground silo disposal at Gyeongju in South Korea. These radioactive wastes contain harmful radionuclides such as Uranium-238 (238U), which can pose long-term and deleterious effects on humans and the natural environment. Ethylenediaminetetraacetic acid and isosaccharinic acid, which can be formed via cellulosic waste degradation under high alkaline conditions might considerably enhance the transport behavior of 238U with the intrusion of rainwater and groundwater. In this study, the engineered barriers (concrete and grout) and natural barriers (sedimentary rock and granite) were used to investigate the 238U transport behavior in artificial cementitious porewater of State I (pH 13.3) and State II (pH 12.5) based on groundwater or rainwater. The surface properties and geochemical compositions of barrier samples were characterized using XRD, XRF, SEM-EDX, and BET. The transport behaviors of 238U in various solution conditions were observed by sorption distribution coefficient (Kd) at a range of initial chelating agents concentration (10-5-10-2 M). The sorption behavior of 238U was retarded more in the engineered rock barriers than in the natural rock barriers. The mobility enhancement of 238U was more significant in State I than in State II. In comparison with the absence of chelating agents, negligible changes in the Kd values of 238U were observed at less than initial chelating agent concentrations of 10-4 M. However, the Kd values of 238U were significantly reduced at initial chelating agent concentrations higher than 10-3 M. Therefore, these experimental findings show that the transport behavior of 238U into the geo- and bio-sphere could be accelerated by the presence of chelating agents and the type of cement degradation states.

Uranium-235, used in nuclear power generation, produces a lot of radioactive waste. Among radioactive waste nuclides, I-129 is problematic due to its long half-life (1.57×107 y) with high mobility in the environment. It should be captured and immobilized into a geological disposal environment through a stable waste form. In this study, various additives including Al, Bi, Pb, V, Mo and W were added to silver tellurite glass to prepare a matrix for immobilizing iodine, and its thermal and leaching properties were evaluated. To prepare glass, the glass precursor mixture was placed in alumina crucibles and heated at 800°C for 1 h. Except for aluminum, there was no significant loss of constituent elements. The loading of iodine in the matrix was approximately 11-15% by weigh, excluding oxygen. The normalized releases of all the elements obtained by PCT-A were below the order of 10-1 g/m2, which satisfies US regulation (2 g/m2). Differential scanning calorimetry was performed to evaluate the thermal properties of the glass samples. The glass transition temperature (Tg) increased by adding such as V2O5, MoO3, or WO3. The similar relative electrostatic field values of V2O5, MoO3, and WO3 could provide sufficient electro static field to the TeO2 interacting with the non-bridging oxygen forming Te-O-M (M = V, Mo, W) links. The addition of MoO3 or WO3 in the silver tellurite glass system increased glass transition temperature (Tg) and crystallization temperature (Tc) while maintaining the glass stability.

A rock joint exerts significant influences on the rock mass behavior in terms of thermal, hydraulic, and mechanical (THM) aspects. Therefore, its features should be thoroughly investigated in various rock mechanical projects, such as high-level radioactive waste (HLW) disposal repository, tunnel, and rock slope. Meanwhile, it is essential to guarantee the safety of the disposal repository for a very long period of time and it should prepare measures for various risks, which may possibly encounter during that period. In general, direct shear tests for a rock joint are conducted to investigate the possibility of frictional sliding of the joint under specific loading conditions or to predict the shear strength of the joint. However, it is necessary to consider whether regional sliding of a rock joint or reactivation of a fault might occur due to an earthquake or redistribution of the in-situ stresses because the expected operation period of the repository is quite long, and various situations can happen. A slide-hold-slide test for a rock joint is a practical test that can investigate the time-dependent behavior or frictionalhealing of a joint. The test enables an estimation of the stress build-up phenomenon after strain energy release in a quantitative manner. In this study, a series of slide-hold-slide tests were carried out in order to investigate the characteristics. Joint specimens were made from mortar, which is a rock-like and brittle material, so as to consider the effect of joint roughness and to secure the reproducibility of the tests. At the same time, mechanical conditions as well as thermal and hydraulic were applied in order to take the environment of the repository into account. As a result, the behavior of shear stress recovery was observed, and the effects of THM coupled condition on the recovery were investigated. This study presents fundamental results of the experiments, and further research outcomes, including time dependent behavior of a joint, will be presented sequentially.

Disposal methods of radioactive waste can be mainly divided into near-surface disposal and deep geological disposal. If the radioactive waste is exposed to groundwater for a long time in the disposal environment, no matter how the decommissioning waste generated from the nuclear power plant is disposed of, the radionuclides may be released from the disposal site. Decommissioning waste from nuclear power plant contains radionuclides that are harmful to ecosystem including humans. Radionuclides released from disposal site behave in a complex and sensitive manner affected by geochemical conditions such as soil, geological media and groundwater. Sorption is one of the important mechanisms to retard the migration of radionuclides in a subsurface environment. In this study, geochemical properties of groundwater were collected and analyzed in the disposal environment considering disposal method in order to evaluate the geochemical behavior of radionuclides. The formation of aqueous and precipitated species of cesium and cobalt in a disposal condition were calculated and estimated. The sorption properties were also evaluated and predicted by considering the changes in the geochemical conditions such as pH, redox potential and geological media for the safety assessment.

Spent nuclear fuels in Korea are temporarily stored at the nuclear power plant site and it is expected that will become saturated from 2031. Deep geological disposal in engineered barrier system (EBS) is one of the most important options for disposing spent nuclear fuel. The disposal canister is the first barrier that prevents leakage of nuclides in the spent nuclear fuel to the environment. Therefore, the corrosion behavior of the canister materials are significant factors in determining the overall disposal period. Oxygen-free copper is the most widely used material for disposal canisters, and manufacturing methods include forging, cold spray, and electro-deposition. In this study, corrosion behavior of materials that have the potential to replace oxygen-free copper manufactured using various 3D printing method were analyzed. As a result of electrochemical analysis of various materials such as copper manufactured by the Atmospheric Plasma Spray (APS) process and Inconel 718 manufactured by the Direct Energy Deposition (DED) process, the possibility of replacing oxygen-free copper was confirmed.

In Korea, borated stainless steel (BSS) is used as spent fuel pool (SFP) storage rack to maintain nuclear criticality of spent fuels. As number of nuclear power plants and corresponding number of spent fuels increased, density in SFP storage rack also increased. In this regard, maintain subcriticality of spent nuclear fuels was raised as an issue and BSS was selected as structural material and neutron absorber for high density storage rack. Because it is difficult to replace storage rack, corrosion resistance and neutron absorbency are required for long period. BSS is based on stainless steel 304 and it is specified in the ASTM A887-89 standard depending on the boron concentration from 304B (0.20-0.29% B) to 304B7 (1.75-2.25% B). Due to low solubility of boron in austenitic stainless steel, metallic borides such as (Fe, Cr)2B are formed as secondary phase metallic borides could make Cr depletion near it which could decrease the corrosion resistance of material. In this paper, long-term corrosion behavior of BSS and its oxide microstructures are investigated through accelerated corrosion experiment in simulated SFP condition. Because corrosion rate of austenitic stainless steel is known to be dependent on the Arrhenius equation, a function of temperature, corrosion experiment is conducted by increasing the experimental temperature. Detail microstructural analysis was conducted with scanning electron microscope, transmission electron microscope and energy dispersive spectrometer. After oxidation, hematite structure oxide film is formed and pitting corrosions occur on the surface of specimens. Most of pitting corrosions are found at the substrate surface because corrosion resistance of substrate, which has low Cr content, is relatively low. Also, oxidation reaction of B in the secondary phase has the lowest Gibbs free energy compared to other elements. Furthermore, oxidation of Cr has low Gibbs free energy which means that oxidation of B and Cr could be faster than other elements. Thus, the long-term corrosion might affect to boron content and the neutron absorption ability of the material.

Irradiated uranium dioxide in damaged used fuel could oxidize during transportation, interim storage or disposal, resulting that the fuel pellet fragments are reduced to a grain-sized powder that can easily escaped from the damaged rod. It has been reported that oxidized spent fuel (i.e. U4O9+x) that was in contact with water could increase the dissolution rate by making the grain boundaries more accessible to the water. Therefore, the damaged used fuel requires stabilization technology including nuclear material recovery, pellet manufacturing process, and stabilization fuel rod manufacturing that can secure safety in terms of permanent disposal. In this study, we prepared pure UO2 and SIMFUEL pellets that are a mixture of UO2 and surrogated metallic oxides for fission products equivalent to a burn-up of 35 GWd/tU and 55 GWd/tU as the stabilized spent fuel. The UO2 and fission products powders were milled and pressed into pellets at 250 MPa and sintered at 1,550°C and 1,700°C for 6 hours in an atmosphere of 4%H2-Ar. The prepared UO2 and SIMFUEL pellets were placed in PTFE Teflon vessels and filled with deionized water to identify the leaching behavior by a long-term leaching experiment under the similar condition to a repository for the safe disposal.

The effect of Li2O addition on precipitation behavior of uranium in LiCl-KCl-UCl3 has been investigated in this study. 99.99% LiCl-KCl eutectic salt is mixed with 10wt% UCl3 chips at 550°C in the Pyrex tube in argon atmosphere glove box, with 10 ppm O2 and 1 ppm H2O. Then, Li2O chunks are added in mixed LiCl-KCl-UCl3 and the system has been cooled down to room temperature for 10 hours to form enough UO2 particles in the salt. The solid salt has been taken out from the glove box, and cut into three sections (top, middle and bottom) by low-speed saw for further microscopic analysis. Three pieces of solid salt are dissolved in deionized water at room temperature and the solution is filtered by a filter paper to collect non-dissolved particles. The filter paper with particles is baked in vacuum oven at 120°C for 6 hours to evaporate remaining moisture from the filter paper. Further analysis was performed for the powder remaining on the filter paper, and periphery of the powder (cake) on the filter paper. Scanning electron microscopy (SEM), electron diffraction spectroscopy (EDS), and X-ray powder diffraction (XRD) are adopted to analysis the characteristic of the particles. From SEM analysis, the powders are consisted of small particles which have 5 to 10 m diameter, and EDS analysis shows they are likely UO2 with 23 at. % of uranium and 77 at. % oxygen. Cake is also analyzed by SEM and EDS, and needle like structures are widely observed on the particle. The length of needle is distributed from 5 to 20 m, and it has 6 to 10 at. % of chlorine, which are not fully dissolved into deionized water at room temperature. From XRD analysis, the particles show the peak position of UO2, and the result is well matched with the SEM-EDS results. We are planning to add more Li2O in the system for fully reacting uranium in UCl3, and compare the results to find the effect of Li2O concentration on UO2 precipitation.

Recently, extreme terrorist attacks have frequently occurred around the world and are threatening the international community. It is no longer a safe zone for terrorism in our country. Therefore, domestic nuclear facilities as the highest level of national security facilities have established a physical protection system to protect facilities and lives against terrorist attacks. In addition, security search and access control are conducted for controlled items and unauthorized person. However, with the development of science and technology, disguised weapons or homemade explosives used in terrorism are becoming very sophisticated. Therefore, nuclear facilities need to strengthen security search of weapons or homemade explosives. Since these disguised weapons or homemade explosives are difficult to find only through security search, it is also necessary to actively identify unspecified people who possess disguised weapons or do abnormal behavior. For this reason, the “Abnormal Behavior Detection Method”, which is very effective in preemptive response to potential terrorist risks, has been introduced and operated in aviation security field. Korea Institute of Nuclear Nonproliferation and Control (KINAC) has established a “Practice Environment for Identifying Disguised Weapons” in 2020 for trainees to recognize the dangers of controlled items and to use for physical protection education. This Practice environment has not only the basic explanation of the controlled items of nuclear facilities, but also various actual disguised weapons were displayed. It also introduces actual terrorist incidents using homemade explosives such as attempted bombing of a cargo plane bound for Chicago and the Boston Marathon bombing. And then a model of the disguised explosives actually used is displayed and used for education. In addition, in 2022, the “Abnormal behavior detection method” education module was developed and used for physical protection education. In this module, the outline and introduction of the “Abnormal Behavior Detection Method” and “Behavior Detection Officer (BDOs)” are explained. In this way, the access control and security search system of nuclear facilities require the overall monitoring system, not only for dangerous goods but also for identification of persons possess and carrying them. This study describes the development of the Curriculum for “Disguised Weapon Identification” and “Abnormal Behavior Detection Method” to enhance the effectiveness of physical protection education.

본 연구는 학원강사를 대상으로 그들의 일터영성, 조직시민행동, 이직의도에 대한 인식 및 개인배경에 따른 차이를 알 아보고, 어떠한 요인들이 조직시민행동 및 이직의도에 영향을 미치는지 파악하는 것을 목적으로 하였다. 궁극적으로 학 원강사의 일터영성과 조직시민행동에 대한 인식을 제고시키고, 학원경영에서 인사관리 방안을 새롭게 모색함으로써 경 영성과를 높이는데 기여하고자 하였다. 연구목적을 달성하기 위해 서울경기 지역의 보습학원, 어학원, 종합학원에 종사 하고 있는 학원강사 426명을 대상으로 설문조사를 통해 자료를 수집하였고, 수집된 자료는 IBM SPSS Statistics 26.0 프 로그램을 이용하여 분석하였다. 주요 연구결과를 종합해보면, 첫째, 학원강사의 일터영성과 조직시민행동에 대한 인식은 보통 수준이었고, 이직의도는 대체로 낮게 나타났다. 둘째, 학원강사의 일터영성, 조직시민행동, 이직의도에 대한 인식은 성별, 연령, 월소득, 결혼여부, 근무경력, 교육정도, 직급, 지도하는 학생층에 따라 대체로 차이가 있었다. 이것은 학원강사의 개인배경을 고려한 인사관 리가 필요하다는 것을 시사해준다. 셋째, 학원강사의 조직시민행동에 영향을 주는 요인은 일터영성의 모든 하위요인과 개인배경의 연령, 결혼여부, 근무경력, 직급, 지도하는 학생층으로 나타났다. 학원강사의 일터영성 및 조직시민행동의 수 준이 높아질수록 학원교육의 질이 좋아질 수 있다는 점에서 학원강사의 일터영성 및 조직시민행동을 증대시키기 위한 학원강사와 학원경영자의 노력이 요구된다.

PURPOSES : The "Super-Bus Rapid Transit" (S-BRT) standard guidelines recommend installing physical facilities to separate bus lanes, so as to remove possible conflicts with other traffic when using an existing road as an S-BRT route. Based on a collision simulation, we reviewed the protective performance and installation method of a low-profile barrier, i.e., one that does not occupy much of the width of the road as a physical facility and does not obstruct the driver's vision. METHODS : The LS-DYNA collision analysis software was used to model the low-profile barrier, and a small car collision simulation was performed with two different installation methods and by changing the collision speeds of the vehicle. The installation methods were divided into a fixed installation method based on on-site construction and a precast method, and collision speeds of 80 and 100 km/h were applied. The weight of the crash vehicle was 1.3 tons, and the segment lengths of the low-profile barriers were 2.5 and 4.0 m, respectively. The lowprofile barriers were modeled as precast concrete blocks, and the collision simulation for a fixed concrete barrier was performed by fixing the nodes at the bottom of the low-profile barrier. The low-profile barrier comprised a square cross-section reinforced concrete structure, and the segments were connected by connecting steel pipes with varying diameters to wire ropes. RESULTS : From comparing and analyzing the small car collision simulations for the changes in collision speeds and installation methods of the low-profile barrier, a significant difference was found in the theoretical head impact velocity (THIV) and acceleration severity index(ASI) for the 2.5-m barrier at a collision speed of 80 km/h. However, the differences in the installation method were not significant for the 4.0-m barrier. The occupant safety index with a collision speed of 80 km/h was calculated to be below the limit regardless of the installation method, and the length of the segment satisfied the occupant protection performance. At a collision speed of 100 km/h, when the segment length of the 2.5-m barrier was fixed, the THIV value exceeded the limit value; thus, the occupant protection performance was not satisfied, and the occupant safety index differed depending on the installation method. The maximum rotation angle of the vehicle, which reflects the behavior of the vehicle after the collision, also varied depending on the installation method, and was generally small in the case of precast concrete. CONCLUSIONS : Low-profile barriers can be installed using a fixed or precast method, but as a result of the simulation, the precast movable barrier shows better results in terms of passenger safety. Therefore, it would be advantageous to secure protection performance by installing a low-profile barrier with the precast method for increased safety in high-speed vehicle collisions.

높아진 생활수준과 주 5일 근무의 정착으로 여가시간이 증가했고, 이에 따라 물을 이용한 공간 에 대한 관심도 크게 증가하였다. 하지만 급격한 양적 성장이 이루어짐에 따라 물놀이 공간은 대부분 획일화된 시설물과 배치로 조성되어 있으며, 다양한 행태에 대한 지원 또한 미흡한 실정이다. 이에 본 연구에서는 빅데이터를 활용한 실증 데이터를 바탕으로 물놀이 공간 및 시설 물의 이용행태를 분석하고자 하였다. 그 결과, 각 물놀이 시설물이 서로 다른 놀이를 지원하며, 각각 유발되는 놀이의 형태나 이용행태가 상이하다는 결론을 도출하였다. 이에 본 연구는 앞으 로 물놀이 공간 조성 시, 물리적 환경과 이용자 간의 관계를 고려하여 설계할 수 있도록 기본자 료를 제시하고자 하였다.

CNTs/Al-Li composite was first prepared by hot-pressed sintering from Al-Li alloy powder and CNTs solution, and then the hot compression tests were performed on MMS-100 thermal simulator at strain rate range of 0.01– 10 s− 1, deformation temperature range of 350–500 °C, and total deformation amount of 60%. True stress–strain curves were plotted, and constitutive equation as well as hot processing maps were successfully confirmed based on Arrhenius constitutive model and Prasad instability criterion. Results show that CNTs/Al-Li composite have a very poor hot deformation ability and narrow processing region, which is strain rate range of 0.1–1 s− 1 and deformation temperature range of 360–400 °C. Hot extrusion experiment was carried out and the processing parameters were selected according to the established hot processing map, and an improvement on strength and a good balance between strength and plasticity can be obtained, which is about 650 MPa for tensile strength and 9% for elongation.