Conducting a TSPA (Total System Performance Assessment) of the entire spent nuclear fuel disposal system, which includes thousands of disposal holes and their geological surroundings over many thousands of years, is a challenging task. Typically, the TSPA relies on significant efforts involving numerous parts and finite elements, making it computationally demanding. To streamline this process and enhance efficiency, our study introduces a surrogate model built upon the widely recognized U-network machine learning framework. This surrogate model serves as a bridge, correcting the results from a detailed numerical model with a large number of small-sized elements into a simplified one with fewer and large-sized elements. This approach will significantly cut down on computation time while preserving accuracy comparable to those achieved through the detailed numerical model.

선박용 엔진에서 배출되는 배기가스에는 다량의 수분과 미세먼지를 포함하고 있다. 미세먼지에는 여과성 미세먼지와 배기 배 출 후 액상으로 변화하는 응축성 미세먼지가 포함되어 있으며 배출 전에 걸러지는 고체상 미세먼지보다 응축성 미세먼지가 더 많은 것으 로 보고되고 있다. 본 연구에서는 배기가스의 배기열과 수분을 회수하고 응축성 미세먼지를 제거하기 위한 실험장치를 실험실 내의 가스 보일러 배기가스를 이용하여 테스트 하였다. 배기가스는 1차적으로 냉각방식으로 수분과 응축성 미세먼지가 제거되고 2차적으로 흡수제 방식에 의해 추가적으로 수분이 제거되었다. 상대습도 측정에 의한 배기가스 수분 제거율을 계산하면 1단계 배기냉각 방식으로 73%, 2단 계 흡수제 방식으로 90% 제거되는 것으로 측정되었다. 이 과정에서 응축성 미세먼지는 80~90% 제거되는 것으로 측정되었다. 개발 시스템 에 의해 회수된 열은 공정열로 활용할 수 있으며, 회수된 물은 수처리 과정을 통해 공정수로 활용할 수 있다. 또한 현재 관리 규제가 되고 있지 않지만 미세먼지의 주요 원인인 응축성 미세먼지를 효과적으로 제거할 수 있을 것으로 기대된다.

국제해사기구(IMO)를 필두로하여 국제적으로 선박에 대한 배출가스 규정을 강화하고 있으며, 대한민국 정부도 온실가스 감축 을 위한 기본 로드맵을 설정하는 등 배출가스 저감을 위한 대책 마련이 절실한 상황이다. 또한, 국내 연안을 항해하는 선박에서 배출되는 온실가스 배출량 중 90.6%를 차지하고 있는 어선에 적용가능한 효율적이고 배출가스량이 감소가능한 새로운 추진시스템의 도입이 절실 하다. 본 연구에서는 국내 연안어선에 적용가능한 전기복합 추진시스템을 제안하고, 전기복합 추진시스템이 적용가능한 대상선박을 선정 하였다. 선정된 기존 대상어선에 탑재된 추진시스템과 비교하여 개발된 전기복합 추진시스템을 적용할 경우 발생할 수 있는 예상 연료소 모량을 비교하기 위한 시뮬레이션 시스템을 Matlab/Simulink를 이용하여 구성하였다. 시뮬레이션을 통해 기계식 추진시스템, 전기복합 추 진시스템(배터리 육상충전을 하지 않은 경우, 육상충전을 한 경우)간의 연료소모량 결과를 확인하였으며 전기복합 추진시스템을 적용하 는 경우 약 13%, 16%의 연료소모량이 감소될 수 있는 것을 보여주는 결과를 확인하였다.

In Korea, five major ports have been designated as sulfur oxide emission control areas to reduce air pollutant emissions, in accordance with Article 10 of the “Special Act on Port Air Quality” and Article 32 of the “Ship Pollution Prevention Regulations”. As regulations against vesseloriginated air pollutants (such as PM, CO2, NOx, and SOx) have been strengthened, the Ministry of Oceans and Fisheries(MOF) enacted rules that newly built public ships should adopt eco-friendly propulsion systems. However, particularly in diesel–electric hybrid propulsion systems,the demand for precise control schemes continues to grow as the fuel saving rate significantly varies depending on the control strategy applied. The conventional Power Take In–Power Take Off(PTI–PTO) mode control adopts a rule-based strategy, but this strategy is applied only in the low-load range and PTI mode; thus, an additional method is required to determine the optimal fuel consumption point. The proposed control method is designed to optimize fuel consumption by applying the equivalent consumption minimization strategy(ECMS) to the PTI–PTO mode by considering the characteristics of the specific fuel oil consumption(SFOC) of the engine in a diesel–electric hybrid propulsion system. To apply this method, a specific fishing vessel model operating on the Korean coast was selected to simulate the load operation environment of the ship. In this study, a 10.2% reduction was achieved in the MATLAB/SimDrive and SimElectric simulation by comparing the fuel consumption and CO2 emissions of the ship to which the conventional rule-based strategy was applied and that to which the ECMS was applied.

Activated corrosion products deposited on the reactor coolant system in a nuclear power plant should be removed to reduce the radiation exposure to workers. Chemical decontamination processes using organic acids have been widely applied to remove the activated corrosion products. However, they are highly corrosive to the base metal and generate a considerable amount of ion exchange resin waste, which is hard to be treated. In order to resolve this problem, KAERI has been developed a chemical decontamination process using chelate-free inorganic acid, HyBRID (Hydrazine Based Reductive metal Ion Decontamination) process. Especially, the Cyclic SP (Sulfuric acid/Permanganate)- HyBRID process was suggested as the decontamination process for applying to the remove the double oxide layer generated on the reactor coolant system in the pressurized water reactor (PWR). During the Cyclic SP-HyBRID process, the process is continuously applied without discharging or recharging of the decontamination process solution from the primary circuit. Thus, it is necessary to include the removal processes of the decontamination reagents middle of the Cyclic SP-HyBRID process, e.g., ‘Mn removal step’ for removing the permanganate ions and ‘hydrazine decomposition step’ for decomposition of the remaining hydrazine. During these removal processes, the metal ions can also be removed from the process solution. In this study, the behaviors of metals were investigated during the Cyclic SP-HyBRID process. The concentration changes of metal ions in the process solution were analyzed using atomic absorption (AA) spectroscopy. The metal precipitates generated during the process were characterized using X-ray diffraction (XRD) and Fourier Transform Infrared (FT-IR) spectroscopy. From the results of the analysis, it was observed that the metal ions dissolved in the process solution were converted into metal hydroxides and precipitated at the Mn removal process. It was confirmed by equilibrium calculation result that the OH− ions generated at the Mn removal can react with the metal ions and form the metal hydroxides. It is considered that this removal behaviors of the metals can contribute the decontamination performance.

The clear-water phase (CWP) is a notable limnological phenomenon in freshwater systems caused by predatory interactions between large filter-feeding zooplankton and phytoplankton. However, the mechanisms and factors that influence the extent of CWP, particularly in complex water systems with both fluvial and lacustrine characteristics, remain poorly understood. The present study evaluated CWP occurrence patterns at different sites in a large reservoir located in a temperate monsoon region (Lake Paldang, Korea); the relationships among factors associated with CWP occurrence, such as transparency, zooplankton diversity, and chlorophyll a concentration were investigated. Transparency exhibited significant correlations with precipitation and retention time, as well as the relative abundance of zooplankton (p<0.01), suggesting that a change in the retention time due to precipitation can alter CWP. Data collected before and after CWP occurrence were analyzed using paired t-test to determine variations in CWP occurrence based on the water system characteristics. The results demonstrated that various factors were associated with CWP occurrence in the fluvial-type and lacustrine-type sites. The correlation between zooplankton biomass and transparency was stronger in the lacustrine-type sites than in the fluvial-type sites. The lacustrine-type sites, where cladoceran emergence is common and is associated with long retention times, favored CWP occurrence. The results suggest that lacustrine-type sites, which are conducive to zooplankton development and have relatively long retention times, enhance CWP occurrence. Furthermore, CWP occurrence was notable in spring, and the present study revealed that site-specific CWP could occur throughout the year, regardless of the season.