The purpose of this study was to compare the efficiency of air and oxygen injected into the underwater non-thermal dielectric barrier discharge plasma (DBD plasma) device used to remove five types of antibiotics (tetracycline, doxycycline, oxytetracycline, clindamycin, and erythromycin) artificially contained in the fish farm discharge water. The voltage given to generate DBD plasma was 27.8 kV, and the measurement intervals were 0, 0.5, 1, 2, 4, 8, 16 and 32 minutes. Tetracycline antibiotics significantly decreased in 4 minutes when air was injected and were reduced in 30 seconds when oxygen was injected. After the introduction of air and oxygen at 32 minutes, 78.1% and 95.8% of tetracycline were removed, 77.1% and 96.3% of doxycycline were removed, and 77.1% and 95.5% of oxytetracycline were removed, respectively. In air and oxygen, 59.6% and 83.0% of clindamycin and 53.3% and 74.3% of erythromycin were removed, respectively. The two antibiotics showed lower removal efficiency than tetracyclines. In conclusion, fish farm discharge water contains five different types of antibiotics that can be reduced using underwater DBD plasma, and oxygen gas injection outperformed air in terms of removal efficiency.

From Fukushima nuclear disaster, as the water which is supplied by rain and groundwater flow into reactor building, contaminated water which contains radioactive nuclides is occurred. Although about 600 tons of contaminated water was generated at the early of accident, as the groundwater management system is developing, about 150 tons of contaminated water is generated now. Tokyo Electric Power Holdings (TEPCO) operate a multi-nuclide removal equipment which is called ‘ALPS’ and store purified water (ALPS treated water) in the Fukushima NPP site by tank. From 2023, the Japanese government decided to dilute the stored ALPS treated water and discharge it into the ocean to secure space on the site. In this study, based on the data opened to the public by TEPCO, the current status of ALPS is investigated. The dilution and discharge process under conceptual design was investigated. In addition, the treatment capacity of ALPS was analyzed based on the radioactivity concentration data of 7 nuclides. And then, two points to be checked found. First, it was confirmed that the performance of ALPS temporarily decreased between 2015 and 2018 due to reduced replacement cycle of filter and absorbent. Second, it was confirmed that the ALPS treated water from specific ALPS still haven’t satisfied the discharge limit for I-129, Sr-90, and Cs-137. In the case of Cs-137, about 1.7 times the radioactivity concentration was detected compared to the discharge limit. For I-129 and Sr-90, about 2.4 times and 2.1 times of radioactivity concentration was detected compared to the discharge limit. From this study, some of the ALPS treated water are confirmed that the radioactivity concentration exceeds the discharge limit, and the treatment capacity of ALPS might be unstable depend on the ALPS operation such as replacement cycle. Therefore, before the discharging of contaminated water on 2023, it is necessary to inspect ALPS if it purifies contaminated water with reliability or not, and to secure the reliable evaluation method to measure radioactivity concentration.

Regulations on the concentration of boron discharged from industrial facilities, including nuclear power plants, are increasingly being strengthened worldwide. Since boron exists as boric acid at pH 7 or lower, it is very difficult to remove it in the existing LRS (Liquid Radwaste System) using RO and ion exchange resin. As an alternative technology for removing boron emitted from nuclear power plants, the electrochemical boron removal technology, which has been experimentally applied at the Ringhal Power Plant in Sweden, was introduced in the last presentation. In this study, the internal structure of the electrochemical module was improved to reduce the boron concentration to 5 mg/L or less in the 50 mg/L level of boron-containing waste liquid. In addition, the applicability of the electrochemical boron removal technology was evaluated by increasing the capacity of the unit module to 1 m3/hr in consideration of the actual capacity of the monitor tank of the nuclear power plant. By applying various experimental conditions such as flow rate and pressure, the optimum boron removal conditions using electrochemical technology were confirmed, and various operating conditions necessary for actual operation were established by configuring a concentrated water recirculation system to minimize secondary waste generation. The optimal arrangement method of the 1 m3/hr unit module developed in this study was reviewed by performing mathematical modeling based on the actual capacity of monitor tank and discharge characteristics of nuclear power plant.

The sewer capacity design have been based on the Huff model or the rational equation in South Korea and often failed to determine optimal capacity, resulting in frequent urban flooding or over-sizing. A time distribution of rainfall (i.e., Huff or ABM method) could be used instead of a rainfall hyetograph obtained from statistical analysis of previous rainfalls. In this study, the Huff method and the ABM method, which predict the time distribution of rain intensity, which are widely used to calculate sewage pipe drainage capacity using the SWMM, were compared with the standard rainfall intensity hyetograph of Seoul. If the rainfall duration was 30 minutes to 180 minutes, the rainfall intensity value calculated by the Huff model tended to be less than the rainfall intensity value of the standard rainfall intensity in the initial 5-10 minutes. As a result, more than 10% to 30% of under-design would be made. In addition, the rainfall intensity value calculated by the Huff model from the section excluding the initial 5-10 minutes of rainfall to the rainfall duration was calculated larger than the value using the standard rainfall intensity equation, which would result in an over-design of 10% to 30%. In the case of a relatively long rainfall duration of 360 minutes (6 hours) to 1,440 minutes (24 hours), it showed an lower rainfall intensity of 60 to 90% in the early stages of rainfall, but the problem of under-design had been solved as the rainfall duration time had elapsed. On the other hand, in the alternating block method (ABM) method, it was found that the rainfall intensity at the entire period at each assumed rainfall duration accurately matched the standard rainfall intensity hyetograph of Seoul.

Tributyl phosphate (TBP) is a well-known and important compound in the nuclear industry for the nuclear fuel reprocessing, and it is also used in a various field such as plastic industry as antifoaming agent. Untreated organic pollutants in TBP can remain in the soil water and cause serious environmental pollution, thus it should be degraded through environmentally friendly methods. The non-thermal plasma-based advanced oxidation process (AOP) is one of the most widely studied and best developed processes owing to its simple structure and ease of operation. In this study, a plasma-based AOP was stably generated using submerged multi-hole dielectric barrier discharge (DBD) and applied to relatively high concentration of TBP solution. A submerged DBD plasma system was designed to directly interact with water, thereby producing reactive oxygen species (ROS) and functioning as a powerful oxidizer. Additionally, UV, O3, and H2O2 are generated by the developed plasma system without using any other additives to produce OH radicals for degrading organic pollutants; therefore, this system circumvents the use of complex and advanced oxidation processes. The electrical properties and concentrations of the active species were analyzed to establish optimal plasma operating conditions for degrading TBP solution. The results were analyzed by measuring the total organic carbon (TOC) and changes in solution properties. Based on these results, a degradation mechanism of TBP solution is proposed. After 50 min of plasma treatment, the concentration of TOC was gradually decreased. Consequently, we found that plasma-based AOP using submerged multi-hole DBD has advantages as an alternative technology for degrading organic pollutants such as TBP solution.

통영 LNG 기지에서 방류되는 냉배수가 진해만에 미치는 영향을 알아보고, 냉배수의 활용 방안 모색을 위해 총 4개의 냉배수 방류량에 대한 진해만의 환경변화를 1년간(2018년) 모의하였다. 실제 냉배수 방류량인 Case1(10 m3 sec-1)의 모의 결과, 모든 분기에서 냉배 수에 의한 진해만의 환경변화는 매우 미미하게 나타났다. 모의 방류량인 Case2(100 m3 sec-1)의 경우 방류구 반경 5 km 범위에서 1 ~ 3℃의 수온 감소를 보였으며, Case3(1000 m3 sec-1)에서는 방류구 반경 8 km 범위에서 최대 4 ~ 5℃의 수온이 감소하였고 진해만 전 해역에 걸쳐 냉 배수가 확산하는 결과를 보였다. 플랑크톤의 성장 속도는 최대 15% 감소하였으며(11월), 대형조류의 성장 속도는 행암만 부근에서 최대 6 % 증가하는 결과를 보였다. 상기 결과로부터 통영 LNG 기지에서 방류되는 냉배수에 의한 진해만의 환경변화는 미미한 것을 확인하였 다. 또한 Case3 결과로부터 국소지역의 ‘적조 방재’, ‘해조류 성장’을 목적으로 냉배수의 활용이 가능할 것으로 기대된다.

We report on the one-step synthesis of luminescent carbon nanodots (C-dots) via an electrical discharge between two graphite electrodes submerged into organic solvent (octane). This is a simple approach for the fabrication of C-dots with tunable photoluminescence (PL) that differs from the other preparation methods, as no post-passivation step is required. The synthesized carbon nanoparticles are of spherical shape and their size is distributed in the range of 2–5 nm and exhibit luminescence sensitive to excitation wavelength.

Nickel nanopowders are obtained by the spark discharge method, which is based on the evaporation of the electrode surface under the action of the discharge current, followed by vapor condensation and the formation of nanoparticles. Nickel electrodes with a purity of 99.99% are used to synthesize the nickel nanoparticles in the setup. Nitrogen is used as the carrier gas with a purity of 99.998%. XRD, TEM, and EDX analyses of the nanopowders are performed. Moreover, HRTEM images with measured interplanar spacings are obtained. In the nickel nanopowder samples, a phase of approximately 90 wt% with an expanded crystal lattice of 6.5% on average is found. The results indicate an unusual process of nickel nanoparticle formation when the spark discharge method is employed.