최근 지구온난화로 인해 폭우, 눈 등 이상기후가 발생하면서 노면 동결(블랙아이스)로 인한 사고 및 인명피해가 늘어나고 있 는 것이 문제가 되고 있다. 이를 최소화하기 위해 본 연구에서는 다공성 골재인 팽창점토에 열저장이 가능한 상변화물질(PCM)을 적용 하였다. PCM은 상변화 과정에서 열에너지를 흡수, 저장, 방출할 수 있는 소재로 온도에 따른 결빙을 최소화할 수 있다. 따라서 본 연 구에서는 시멘트 복합재에 적용되는 PCM 함침이 가능한 경량골재에 진공함침을 실시하고 기계적, 열적 성능 검증 연구를 수행하였다. 열적 성능을 향상시키기 위해 다중벽탄소나노튜브(MWCNT)와 실리카흄을 첨가하였다. 본 연구에서는 물체의 열적 성능을 측정할 수 있는 DSC 실험을 통해 PCM 함침 경량골재 및 콘크리트 복합체의 열적 성능을 검증하였다. 콘크리트 복합체 제작 후 압축강도 시험 과 열적 성능시험을 실시하였다. 이때 열적 성능을 검증하기 위해 항온항습 챔버를 이용하여 시험을 진행하였다. 압축강도 실험을 통 해 MWCNT의 분삭액을 혼입한 PCM 함침 팽창점토가 적용된 콘크리트 복합체의 평균 압축강도는 24MPa 이상으로 구조물에 적용이 가능함을 확인하였다. 열적 성능시험을 통해 PCM 함침 팽창점토가 적용된 콘크리트 복합체는 영하의 외기온도에서도 영상의 온도를 유지할 수 있음을 확인하였다. 이와 같은 결과를 통해 주거 및 상업 건물 및 다양한 구조물에 적용이 가능할 것으로 판단된다.

본 연구는 축산시설 내 설치된 무창기공형 집열기의 배기 방향 및 유량 변화를 통해 벽체에 전달되는 일사를 차단, 이를 통한 냉방효과를 검증하려는 목적의 기초 연구로서 무창기공형 집열기 시험장치를 제작, 배기 유량 변화에 따른 위치별 온도 변화 및 이를 통한 열성능 평가를 수행하였다. 실험 결과, 무창기공형 집열기의 유량조건별 집열판 표면온도는 최고 27.7℃, 배기온도는 최고 약 10.9℃ 온도 차이를 확인하였다. 무창기공형 집열기의 유량조건별 열교환 유효도는 0.48∼0.62, 효율은 30%∼90%의 분포로 나타났다. 집열판 에너지는 유량이 증가함에 따라 감소, 집열기 내부 에너지는 유량이 증가함에 따라 증가하였다. 이를 통해 농업시설 외벽에 설치된 무창기공형 집열기의 여름철 미운용으로 인한 집열판 및 내부 온도상승과 이로 인한 벽체로의 열전달 등 무창기공형 집열기로 인한 역효과를 방지할 수 있을 뿐만 아니라 집열기 외부로의 강제 배기를 통해 벽체로 직접 투입되는 일사 차단을 통한 냉방효과 또한 구현할 수 있을 것으로 판단된다.

최근 지구온난화로 인해 발생하는 폭우 및 강설과 같은 비정상적인 기상 패턴으로 인해 도로 표면 결빙(블랙 아이스)으로 인 한 사고와 인명 피해가 증가하고 있으며, 이는 주요 문제로 대두되고 있습니다. 이러한 문제를 완화하기 위해 본 연구에서는 열저장 능력을 갖춘 상변화 물질(PCM)을 시멘트 복합재료에 포함시켰습니다. PCM은 상변화 과정에서 열에너지를 흡수, 저장 및 방출할 수 있어 온도 변동으로 인한 결빙을 최소화할 수 있습니다. PCM은 먼저 미세 캡슐화된 후 시멘트 복합재료에 강화되어 기계적 및 열적 성능 검증 연구가 수행되었습니다. 또한, 열전달 효율과 기계적 특성을 향상시키기 위해 다중벽 탄소나노튜브(CNT)와 실리카 퓸이 추 가되었습니다. 미세 캡슐화된 PCM의 열 성능은 열 거동을 측정하기 위한 재료 실험을 통해 검증되었습니다. 이후, 제조된 시멘트 복 합재의 기계적 및 열적 성능 테스트가 그 효과를 평가하기 위해 수행되었습니다. 이러한 테스트 동안 일정 온도와 습도 챔버를 사용한 열 주기 테스트가 열 성능을 검증하기 위해 수행되었습니다. 기계적 성능 실험에서는 CNT와 실리카 퓸의 포함이 미세 캡슐화된 PCM 의 포함으로 인한 강도 저하를 완화하는 것을 확인하였습니다. 더욱이, 열 주기 테스트를 통해 고효율 열저장 시멘트 복합재가 결빙 조건에서도 영하의 온도를 유지할 수 있음을 보여주었으며, 이는 효율적인 열저장 성능을 입증하였습니다.

The bentonite buffer material is a crucial component in an engineered barrier system used for the disposal of high-level radioactive waste. Because a large amount of heat from the disposal canister is released into the bentonite buffer material, the thermal conductivity of the bentonite buffer is a crucial parameter that determines the design temperature. At the Korea Atomic Energy Research Institute (KAERI), a new standard bentonite (Bentonil-WRK) has been used since 2022 because Gyeongju (KJ) bentonite is no longer produced. However, the currently available data are insufficient, making it essential to investigate both the basic and complex properties of Bentonil-WRK. Thus, this study evaluated its geotechnical and thermal properties and developed a thermal conductivity empirical model that considers its dry density, water content, and temperature variations from room temperature to 90°C. The coefficient of determination (R2) for the model was found to be 0.986. The thermal conductivity values of Bentonil-WRK were 1–10% lower than those of KJ bentonite and 10–40% higher than those of MX-80 bentonites, which were attributable to mineral-composition differences. The thermal conductivity of Bentonil-WRK ranged between 0.504 and 1.149 W·(m−1·K−1), while the specific heat capacity varied from 0.826 to 1.138 (kJ·(kg−1·K−1)).

Numerous factors contribute to the deterioration of reinforced concrete structures. Elevated temperatures significantly alter the composition of the concrete ingredients, consequently diminishing the concrete's strength properties. With the escalation of global CO2 levels, the carbonation of concrete structures has emerged as a critical challenge, substantially affecting concrete durability research. Assessing and predicting concrete degradation due to thermal effects and carbonation are crucial yet intricate tasks. To address this, multiple prediction models for concrete carbonation and compressive strength under thermal impact have been developed. This study employs seven machine learning algorithms—specifically, multiple linear regression, decision trees, random forest, support vector machines, k-nearest neighbors, artificial neural networks, and extreme gradient boosting algorithms—to formulate predictive models for concrete carbonation and thermal impact. Two distinct datasets, derived from reported experimental studies, were utilized for training these predictive models. Performance evaluation relied on metrics like root mean square error, mean square error, mean absolute error, and coefficient of determination. The optimization of hyperparameters was achieved through k-fold cross-validation and grid search techniques. The analytical outcomes demonstrate that neural networks and extreme gradient boosting algorithms outshine the remaining five machine learning approaches, showcasing outstanding predictive performance for concrete carbonation and thermal effect modeling.

The thermal evaluations for the conceptual design of the deep geological repository considering the improved modeling of the spent fuel decay heat were conducted using COMSOL Multiphysics computational program. The maximum temperature at the surface of a disposal canister for the technical design requirement should not exceed 100°C. However, the peak temperature at the canister surface should not exceed 95°C considering the safety margin of 5°C due to several uncertainties. All thermal evaluations were based on the time-dependent simulation from the emplacement time of the canister to 100,000 years later. In particular, the heat source condition was set to the decay heat rate and axial decay heat profile of the PLUS7 fuel with 4.0wt% U-235 and 45 GWD/MTU. The thermal properties of the granitic rock in South Korea were applied to the host rock region. For the reference design case, the cooling time of the SNF was set to 40 years, the distance between the deposition holes 8 meters and that between the deposition tunnels 30 meters. However, the peak temperature at the canister surface at 10 years was 95.979°C greater than 95°C. This design did not meet the thermal safety requirement and needed to be modified. For the first modified case, when the distance between the deposition tunnels was set to 30 meters, three cooling time cases of 40, 50 and 60 years and five distances of 6, 7, 8, 9 and 10 meters between the deposition holes were considered. The design with the distances of 9 and 10 meters between the deposition holes for the cooling time of 40 years and all five distances for 50 and 60 years were less than 95°C. For the second modified case, when the distance between the deposition holes was set to 8 meters, three cooling time cases of 40, 50 and 60 years and five distances of 20, 25, 30, 35 and 40 meters between the deposition tunnels were considered. The design with the distances of 35 and 40 meters between the deposition tunnels for the cooling time of 40 years, the distances of 25, 30, 35 and 40 meters for 50 years and all five distances for 60 years were less than 95°C. As a result, the peak temperature at the canister surface decreased as the cooling time and the distance between the deposition holes and the tunnels increased.

상변화 물질(PCM)은 상전이 동안 에너지를 흡수하거나 방출할 수 있는 잠열 저장 물질로 활용된다. 최근 수십 년 동 안, 연구자들은 다양한 온도 적용을 위한 건설 물질로의 다양한 PCM의 통합을 탐구해 왔다. 그러나, PCM을 통합하는 콘크리트 의 기계적 및 열적 반응은 통합 방법에 의해 영향을 받는다. PCM을 콘크리트에 추가하기 위한 여러 기술이 제안되었다. 그럼 에도 불구하고, 콘크리트에 마이크로 캡슐화 PCM(m-PCM)의 통합은 종종 기계적 강도의 상당한 감소를 초래한다. 기존 콘크리 트에 m-PCM의 추가와 관련된 한계를 극복하기 위해, 예외적인 강도 및 내구성 특성으로 인해 초고성능 시멘트 복합체(UHPCC) 가 선호된다. 따라서, 본 연구에서는 기존 기술의 단점을 해결하기 위해 PCM을 통합한 신규 나노 엔지니어링 UHPCC를 개발하 였다. 또한, 시멘트 복합체의 기계적 및 열적 성능을 향상시키기 위해 다중 벽 탄소 나노튜브(MWCNT)를 추가하였다. 결과는 MWCNT의 포함이 기계적 성능을 향상시켰을 뿐만 아니라 시멘트 복합체의 열적 성능을 향상시켰다는 것을 보여 주었다.

With the increasing number of aging buildings across Korea, emerging maintenance technologies have surged. One such technology is the non-contact detection of concrete cracks via thermal images. This study aims to develop a technique that can accurately predict the depth of a crack by analyzing the temperature difference between the crack part and the normal part in the thermal image of the concrete. The research obtained temperature data through thermal imaging experiments and constructed a big data set including outdoor variables such as air temperature, illumination, and humidity that can influence temperature differences. Based on the collected data, the team designed an algorithm for learning and predicting the crack depth using machine learning. Initially, standardized crack specimens were used in experiments, and the big data was updated by specimens similar to actual cracks. Finally, a crack depth prediction technology was implemented using five regression analysis algorithms for approximately 24,000 data points. To confirm the practicality of the development technique, crack simulators with various shapes were added to the study.

Many countries have used nuclear power to generate electricity. Uranium-235, which is used as fuel in nuclear power plants, produces many fission products. Among them, iodine-129 is problematic due to its long half-life (1.57×107 years) and high diffusivity in the environment. If it is released into the environment without any treatment, it could have a major impact on humans and ecosystems. Therefore, it must be treated into a stable form through capture and solidification. Iodine can be captured in the form of AgI through silver-loaded zeolite filters in off-gas treatment processes. However, AgI could be decomposed in the reducing atmosphere of groundwater, so it must be converted into a stable form. In this study, Al2O3, Bi2O3, PbO, V2O5, MoO3, or WO3 were added to the iodine solidification matrix, AgI-Ag2O-TeO2 glass. The glass precursors were mixed to the appropriate composition and placed in an alumina crucible. After heat treatment at 800°C for 1 hour, the melt was quenched in a carbon crucible. The leaching behavior and thermal properties of the glass samples were evaluated. The PCT-A test for leaching evaluation showed that the normalized releases of all elements were below 2 g/m2, which satisfied the U.S. glass wasteform leaching regulations. Diffrential scanning calorimetry (DSC) was performed to evaluate the thermal properties of all glass samples. The addition of MoO3 or WO3 to the AgI-Ag2O-TeO2 glass increased the glass transition temperature (Tg) and crystallization temperature (Tc) while maintaining the glass stability. The similar relative electro-static filed values of MoO3, and WO3 which are approxibately three times that of the glass network former TeO2, could provide sufficient force to the TeO2 interacting with the non-bridging oxygen forming Te-O-M (M=V, Mo, W) links. The high electrostatic forces of Mo and W increased the glass network cohension and prevented the crystallization of the glass.

Heat-generating nuclides such as Cs-137 and Sr-90 should be separated from spent nuclear fuel to reduce the short-term thermal load on the repository facility. In particular, Sr-90 must be separated because its decay process generates high temperatures. Recently, the Korea Atomic Energy Research Institute (KEARI) has been developing a waste burden minimization technology to reduce the environmental burden resulting from the disposal of spent nuclear fuel and maximize the utilization of the disposal facility. The technology incorporates a nuclide management process that maximizes disposal efficiency by selectively separating and accumulating key nuclides from spent nuclear fuel, such as Cs, Sr, I, TRU/RE, and Tc/Se. Sr nuclides dissolve in the chloride phase during the chlorination process of spent nuclear fuel and are recovered as carbonate or oxide through reactive distillation or reactive crystallization. Due to their chemical similarity, Ba nuclides are recovered along with Sr nuclides during this process. In this study, we prepared a ceramic waste form for group II nuclides, Ba(x)Sr(1-x)TiO3 (x=0, 0.25, 0.5, 0.75, 1), using the solid-state reaction method, taking into account the different ratios of Sr/Ba nuclides produced during the nuclide management process. Regardless of the Sr/Ba ratio, the established waste form fabrication process was able to produce a stable waste form. Physicochemical properties, including leaching and thermal properties, were evaluated to determine the stability of group II waste forms. In addition, the radiological properties of waste forms of Ba(x)Sr(1-x)TiO3 with varying Sr/Ba ratios were evaluated. These results provided fundamental data for the long-term storage and management of waste forms containing group II nuclides.

There have been a variety of issues related to spent nuclear fuel in Korea recently. Most of the issues are related to intermediate storage and disposal of spent nuclear fuel. However, recently, various studies have been started in advanced nuclear countries such as the United States to reduce spent nuclear fuel, focusing on measures to reduce spent nuclear fuel. In this study, a simple preliminary assessment of the thermal part was performed for the consolidation storage method which separates fuel rods from spent nuclear fuel and stores them. The preliminary thermal evaluation was analyzed separately for storing the spent fuel in fuel assembly state and separating the fuel rods and storing them. The consolidation storage method in separating the fuel rods was advantageous in terms of thermal conductivity. However, detailed evaluation should be performed considering heat transfer by convection and vessel shape when storing multiple fuel bundles simultaneously.

This study sought to conduct a fundamental investigation in order to test and evaluate the thermal performance of an aluminum stick curtain wall system. In terms of the thermal performance index, the infiltration rate of air tightness, thermal transmittance of the heat insulation property and temperature difference ratio of condensation resistance were experimentally measured. The research process can be divided into three parts. First of all, a database for the test report of the curtain wall was compiled and existing design criteria with respect to the evaluation method and standard of transparent building components such as curtain wall, window and door were analyzed to produce the specimens. Secondly, four different types of curtain wall specimens were created through investigating the curtain wall database. Thirdly, standard tests of thermal performance were carried out for airtightness, thermal performance and condensation resistance. As a result, the curtain wall specimens with low-e triple glazing covered by an aluminum capture system showed high thermal performance compared to other curtain wall specimens including low-e triple glazing with a 4-sided structural sealant glazing system. Air tightness of all types of curtain wall specimens satisfied level 1 standard for air tightness. It was found that a curtain wall which consists of a one track frame has difficulties meeting the residential standard of thermal performance with regard to thermal transmittance and condensation resistance.

PURPOSES : In this study, the thermal conductivity properties and mechanical performance of a thermally conductive asphalt mixture that can be applied to increase the efficiency of deicing asphalt pavements are evaluated. METHODS : Graphite powder and carbon fiber, which are inexpensive carbon materials, were added to the asphalt mixture to its conductivity. To determine the optimal mixing ratio of the carbon materials, the dispersibility, thermal conductivity, and performance of the conductive asphalt mixture were evaluated. The performance of the mixture was evaluated in terms of its volume characteristics, Marshall stability, dynamic modulus, indirect tensile strength (IDT), and wheel-tracking tests. RESULTS : The thermal conductivity of the asphalt mixture containing 2% graphite is 1.81 W/mK, which is approximately twice (0.94 W/mK) that of a general asphalt mixture. Meanwhile, the graphite-added asphalt mixture indicates a much higher temperature increase rate than the general asphalt mixture, and its surface temperature after 60 min is 7.5 ℃ higher. In addition, it reaches 0 ℃ from -10 ℃ at a rate 1.5 times higher than that required by the general asphalt mixture. When both 2% graphite and 1% carbon fiber are added, the thermal conductivity improves to 2.03 W/mK, and the conductivity is similar at all locations of the slab specimen location, which indicates no dispersibility issue. The results of the mechanical performance evaluation shows that the higher the ratio of the carbon material, the lower is the dynamic modulus and IDT at 20 ℃, which decreases the crack resistance. Meanwhile, the results of the Hamburg wheel-tracking test at 50 ℃ show an improvement in the permanent deformation resistance. CONCLUSIONS : The results of the conductivity and performance evaluation show that the optimal ratio is the combination of 2% graphite and 0.5% carbon fiber. This suggests that the conductive asphalt mixture incorporated with carbon materials can efficiently transfer heat generated from the heating layer at the bottom of the pavement to the pavement surface.

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.

The safety of a KTC-360 transport cask, a large-capacity pressurized heavy-water reactor transport cask that transports CANDU spent nuclear fuel discharged from the reactor after burning in a pressurized heavy-water reactor, must be demonstrated under the normal transport and accident conditions specified under transport cask regulations. To confirm the thermal integrity of this cask under normal transport and accident conditions, high-temperature and fire tests were performed using a one-third slice model of an actual KTC-360 cask. The results revealed that the surface temperature of the cask was 62°C, indicating that such casks must be transported separately. The highest temperature of the CANDU spent nuclear fuel was predicted to be lower than the melting temperature of Zircaloy-4, which was the sheath material used. Therefore, if normal operating conditions are applied, the thermal integrity of a KTC-360 cask can be maintained under normal transport conditions. The fire test revealed that the maximum temperatures of the structural materials, stainless steel, and carbon steel were 446°C lower than the permitted maximum temperatures, proving the thermal integrity of the cask under fire accident conditions.

Uranium-235, used for nuclear power generation, has brought radioactive waste. It could be released into the environment during reprocessing or recycling of the spent nuclear fuel. Among the radioactive waste nuclides, I-129 occurs problems due to its long half-life (1.57×107 y) with high mobility in the environment. Therefore, it should be captured and immobilized into a geological disposal system through a stable waste form. One of the methods to capture iodine in the off-gas treatment process is to use silver loaded zeolite filter. It converts radioactive iodine into AgI, one of the most stable iodine forms in the solid state. However, it is difficult to directly dispose of AgI itself in an underground repository because of its aqueous dissolution under reducing condition with Fe2+. It must be immobilized in the matrix materials to prevent release of iodine as a result of chemical reaction. Among the matrix glasses, silver tellurite glass has been proposed. In this study, additives including Al, Bi, Pb, V, Mo, and W were added into the silver tellurite glass. The thermal properties of each matrix for radioactive iodine immobilization were evaluated. The glasses were prepared by the melt-quenching method at 800°C for 1 h. Differential scanning calorimetry (DSC) was performed to evaluate the thermal properties of the glass samples. From the study, the glass transition temperature (Tg) was increased by adding additives such as V2O5, MoO3, or WO3 in the silver tellurite glass. The relative electro-static field (REF) values of V2O5, MoO3, and WO3 are about three times higher than that of the glass network former, TeO2. It could provide sufficient electro-static field (EF) to the TeO2 interacting with the non-bridging oxygen forming Te-O-M (M = V, Mo, W) links. Therefore, the addition of V2O5, MoO3, or WO3 reinforced the glass network cohesion to increase the Tg of the glass. The addition of MoO3or WO3 in the silver tellurite glass increased Tg and crystallization temperature (Tc) with remaining the glass stability.