The saturation of wet storage facilities constructed and operated within nuclear power plant sites has magnified the significance of research concerning the dry storage of spent nuclear fuel. Not only do wet storage facilities incur higher operational and maintenance costs compared to dry storage facilities, but long-term storage of metal-clad fuel assemblies submerged in aqueous tanks is deemed unsuitable. Consequently, dry storage is anticipated to gain prominence in the future. Nevertheless, it is widely acknowledged that quantitatively assessing the residual water content remains elusive even when employing the apparatus and procedures utilized in the existing dry storage processes. The presence of residual water can only be inferred from damage or structural alterations to the spent nuclear fuel during its dry storage, making precise prediction of this element crucial, as it can be a significant contributor to potential deformations and deterioration. The aforementioned challenges compound the issue of retrievability, as substantial complexities emerge when attempting to retrieve spent nuclear fuel for permanent disposal in the future. Consequently, our research team has established a laboratory-scale vacuum drying facility to investigate the sensitivity of various parameters, including canister volume, pump capacity, water surface area, and water temperature, which can exert thermohydraulic influences on residual water content. Moreover, we have conducted dimensional analysis to quantify the thermohydraulic effects of these parameters and express them as dimensionless numbers. These analytical approaches will subsequently be integrated into predictive models for residual water content, which will be further developed and validated at pilot or full-scale levels. Furthermore, our research team is actively engaged in experimental investigations aimed at fine-tuning the duration of the pressure-holding phase while optimizing the evaporation process under conditions designed to avert the formation of ice caused by abrupt temperature fluctuations. Given that the canister is constructed from acrylic material, we are able to identify, from a phenomenological perspective, the specific juncture at which the boiling phenomenon becomes manifest during the vacuum drying process.

For the decommissioning or continuous long-term power generation of nuclear power plants, it is necessary to transfer the spent nuclear fuel from the wet storage pool to the dry storage. Spent nuclear fuel should go through the drying process, which is the first step of dry storage. The most important part in the drying process is the removal of the residual water. The spent fuel might be stored in a dry storage system for a long time. The integrity of internal components and spent fuel cladding should be maintained during the storage period. If residual water is present, problems such as aging of metal materials, oxidation of cladding, and the hydride-reorientation could occur. The presence or absence of residual water after vacuum drying is evaluated by pressure. If there is residual water in the vacuum drying process, it evaporates easily at low pressure to form water vapor pressure and the internal pressure rises. In the recent EPRI High burn up demonstration test, the gas inside the canister that satisfied the dryness criteria was extracted and analyzed. It showed that the water content was higher than the expected value. We are conducting verification studies on the pressure evaluation method, which is an indirect evaluation method of vacuum drying. The vacuum drying test was performed on small specimens at Sandia National Laboratory, and quantitative residual water evaluation was also performed. The report did not mention a detailed method for the assessment of residual water. Based on the test results of SNL, direct residual water evaluation was performed using energy balance. If the dryness criteria were satisfied, the quantitative amount of residual water was also evaluated. As a result, almost the same result as the evaluation result of SNL was derived, and it was confirmed that most of the water was removed when the dryness criteria was satisfied.

For Dry Storage of Spent Nuclear Fuel (SNF), all moisture must be removed from the dry storage canister through subjected to a drying process to ensure the long-term integrity. In NUREG-1536, the evacuation of most water contained within the canister is recommended a pressure of 0.4 kPa (3 torr) to be held in the canister for at least 30 minutes while isolated from active vacuum pumping as a measure of sufficient dryness in the canister. In the existing drying process, the determination of drying end point was determined using a dew point sensor indirectly. Various methods are being studied to quantify the moisture content remaining inside the canister. We presented a moisture quantification method using the drying process variables, like as temperature, pressure, and relative humidity operation data. During the drying process, it exists in the form of a mixed gas of water vapor and air inside the canister. At this time, if the density of water vapor in the mixed gas discharged out of the canister by the vacuum pump is known, the mass of water removed by vacuum drying can be calculated. The canister is equipped with a pressure gauge, thermometer and dew point sensor. The density of water vapor is calculated using the pressure, temperature and relative humidity of the gas obtained from these sensors. First, calculate the saturated water vapor pressure, and then calculate the humidity ratio. The humidity ratio refers to the ratio of water vapor mass to the dry air mass. After calculating the density of dry gas, multiply the density by the humidity ratio to calculate the density of water vapor (kg/m3). Multiply the water vapor density by the volume flow (m3/s) to obtain the mass value of water (kg). The calculated mass value is the mass value obtained per second since it is calculated through the flow data obtained every second, and the amount of water removed can be obtained by summing all the mass values. By comparing this value with the initial moisture content, the amount of moisture remaining inside the canister can be estimated. The validity of the calculations will be verified through an experimental test in the near future. We plan to conduct various research and development to quantify residual water, which is important to ensure the safety of the drying process for dry storage.

This study was conducted to evaluate the degradation and mineralization of PPCPs (Pharmaceuticals and Personal Care Products) using a CBD(Collimated Beam Device) of UV/H2O2 advanced oxidation process. The decomposition rate of each substance was regarded as the first reaction rate to the ultraviolet irradiation dose. The decomposition rate constants for PPCPs were determined by the concentration of hydrogen peroxide and ultraviolet irradiation intensity. If the decomposition rate constant is large, the PPCPs concentration decreases rapidly. According to the decomposition rate constant, chlortetracycline and sulfamethoxazole are expected to be sufficiently removed by UV irradiation only without the addition of hydrogen peroxide. In the case of carbamazepine, however, very high UV dose was required in the absence of hydrogen peroxide. Other PPCPs required an appropriate concentration of hydrogen peroxide and ultraviolet irradiation intensity. The UV dose required to remove 90% of each PPCPs using the degradation rate constant can be calculated according to the concentration of hydrogen peroxide in each sample. Using this reaction rate, the optimum UV dose and hydrogen peroxide concentration for achieving the target removal rate can be obtained by the target PPCPs and water properties. It can be a necessary data to establish design and operating conditions such as UV lamp type, quantity and hydrogen peroxide concentration depending on the residence time for the most economical operation.

This study aimed to develop a method to optimize residual chlorine concentrations in the process of providing water supply. To this end, this study developed a model capable of optimizing the chlorine input into the clearwell in the purification plant and the optimal installation location of rechlorination facilities, and chlorine input. This study applied genetic algorithms finding the optimal point with appropriate residual chlorine concentrations and deriving a cost-optimal solution. The developed model was applied to SN purification plant supply area. As a result, it was possible to meet the target residual chlorine concentration with the minimum cost. Also, the optimal operation method in target area according to the water temperature and volume of supply was suggested. On the basis of the results, this study derived the most economical operational method of coping with water pollution in the process of providing water supply and satisfying the service level required by consumers in the aspects of cost effectiveness. It is considered possible to appropriately respond to increasing service level required by consumers in the future and to use the study results to establish an operational management plan in a short-term perspective.

Oxidation of erythromycin, sulfamethazine and sulfathiazole by ozone was experimentally investigated to see the effects of background water quality such as ultrapure water, humic acid and biologically treated wastewater and water temperature on the removal rate, consequently to provide design information when the ozone treatment process is adopted. Initial concentration of the antibiotics was spiked to 10 μg/l and ozone dose was 1, 2, 3, 5, 8 mg/l. While the removal rate of erythromycin under ultrapure water background by ozone oxidation was over 99%, that under humic acid and biologically treated wastewater background was markedly reduced to the range of 59.8%~99% and 17.0%~99%, respectively. When water temperature is decreased from 20℃ to 4℃, the removal rate is reduced from the range of 17.0%~99% to the range of 9.4%~97.4% under biologically treated wastewater background. The effects of background and temperature on the removal rate of sulfamethazine and sulfathiazole were similar to erythromycin, but the degree was different. Therefore, it is concluded that the background of water to be treated as well as water temperature should be taken into consideration when the design factor such as ozone dose is determined to meet the treatment objective in the ozone treatment process.

수처리에 있어 막여과 기술은 안전한 처리수질의 보장, 시스템의 집약화 및 자동화 등의 장점으로 인해 활발히 도입되고 있다. 하지만 핵심 기자재인 막 모듈의 설계나 전체 정수처리 공정의 안정성 부분에 대해서는 아직 기술개발의 여지가 남아 있다. 본 연구에서는 막여과 공정의 연속 운전에 있어서 막오염을 완화시키기 위한 목적으로 수행하는 물리적인 역세척의 효율 향상과 더불어 이 때 발생하는 역세배출수를 막 모듈 외부로 원활히 배출할 수 있도록 한 가압식 막여과 기술과, 이 때 발생한 가압식 막여과 배출수를 이중 구조로 구획된 침지 막조 이용하여 원활히 처리할 수 있는 침지식 막여과 기술을 결합하여 기존 기술에 비해 고회수율의 달성은 물론, 집약적이고 실용적인 2단 막여과 정수처리 시스템을 개발하고자 하였다.

This study attempts to draw factors for an analysis of the operation effect of a rechlorination facility and autodrain equipment for residual chlorine equalization by installing and operating a rechlorination facility and autodrain equipment in P City and analyzing the practical evaluation method and operation effect. For this purpose, this study selected three indicators for an analysis of the effectiveness of residual chlorine equalization and conducted a comparative analysis before and after the implementation of the residual chlorine equalization. As a result of estimation, ① the reduction of the residual chlorine concentration range from a water treatment plant to the pipe end was 16.0%; ② the total reduction of chlorination input was 18.0%; and ③ the reduction of the generation of disinfection by-products was 19.5%. In addition, this achieved enough residual chlorine equalization in the supply process and shows that it could successfully achieve the economic feasibility of investment in equipment and the reduction of the generation of disinfection by-products. Like this, it is judged that the three indicators suggested in this study will be used sufficiently as indicators of an analysis of the effectiveness of residual chlorine equalization according to the operations of the rechlorination facility and autodrain equipment.

The aim of this study was to evaluate the chemical quenching system for residual ozone and to determine the operating condition for the quenching system. Hydrogen peroxide (H₂O₂) and sodium thiosulfate (Na₂S₂O₃) were investigated as quenching reagents for ozone removal, and the tendency of each chemical was notably different. In the case of H₂O₂, the degradation rate of ozone was increased as the concentration of H₂O₂ increase, and temperature and pH value have a significant effect on the degradation rate of ozone. On the other hand, the degradation rate of ozone was not affected by the concentration of Na₂S₂O₃, temperature and pH value, due to the high reactivity between the S₂O₃²- and ozone. This study evaluates the decomposition mechanism of ozone by H₂O₂ and Na₂S₂O₃ with consideration for the water quality and reaction time. Furthermore, the removal test for the quenching reagents, which can be remained after reaction with ozone, was conducted by GAC process.

It is important to predict chlorine decay with different water purification processes and distribution pipeline materials, especially because chlorine decay is in direct relationship with the stability of water quality. The degree of chlorine decay may affect the water quality at the end of the pipeline: it may produce disinfection by-products or cause unpleasant odor and taste. Sand filtrate and dual media filtrate were used as influents in this study, and cast iron (CI), polyvinyl chloride (PVC), and stainless steel (SS) were used as pipeline materials. The results were analyzed via chlorine decay models by comparing the experimental and model parameters. The models were then used to estimate rechlorination time and chlorine decay time. The results indicated that water quality (e.g. organic matter and alkalinity) and pipeline materials were important factors influencing bulk decay and sand filtrate exhibited greater chlorine decay than dual media filtrate. The two-component second-order model was more applicable than the first decay model, and it enabled the estimation of chlorine decay time. These results are expected to provide the basis for modeling chlorine decay of different water purification processes and pipeline materials.

Various treatment system for residuals have applied to save water resources, but most of them were not be satisfied with legal standard consistently. In this study, submerged membrane treatment system was operated to treat water treatment plant residuals and operation parameters was evaluated. Result of this experiment, high concentration organic matters contributed to high increase Transmembrane pressure(TMP) of membrane system(from 0.05 bar to 0.35 bar). And backwash process was effective to stabilize membrane system operation. After Cleaning-In-Place(CIP), permeability was recovered about 100 % from first operation condition. Inorganic matters (Fe, Mn, Al, Ca, Mg) were not effective membrane filtration performance. The quality of residual treatment was satisfied with drinking water quality standard and a treated water from that system was suitable for water reuse.

Analysis of design parameters of residual treatment process at eight model water treatment plants, which were located in the four major watersheds, showed that there were large differences between those design parameters and the actual conditions. In this background, a new procedure was proposed and applied to the Chungju water treatment plant as an example of the optimum design of residual treatment process based on the characteristics of raw water. In this design example, a filter backwash recycle system consisting of a surging tank and sedimentation basin was newly proposed for more safe recycle of spent backwash water. It is expected that the design procedure proposed in this study would be estimated as a meaningful attempt to develope new design procedure for the domestic water industry.

본 논문에서는 상수관로의 효율적인 유지 관리를 위해 상수도 기술진단에서 점수평가법으로 도출된 관망성능평가결과를 이용한 상수도 관로의 내구연수 및 잔존수명 산정 방법을 제시하였다. 본 연구에서 잔존수명은 ‘모델에 의해 추정된 매설 후 최적교체시기까지 경과년수’를 의미하는 ‘내구연수’와 매설 후 경과년수의 차이로 정의하였으며, 내구연수는 관망성능평가기준으로 제시된 노후관로 판정기준 점수에 도달하는 시점으로 정의하였다. 연구대상지역의 관망성능평가에 사용된 평가항목들과 노후도 점수를 상수도 관로의 잔존수명 추정을 위한 다중회귀모델의 변수로 사용하였다. 잔존수명의 산정에 필요한 내구연수를 추정하기 위하여 구축된 회귀모델에 독립변수로 사용된 노후도 점수를 나타내는 변수의 값으로 노후관로 판정기준 점수에 해당하는 값을 대입하였다. 개발된 회귀모델을 이용하여 연구대상지역 상수도 관로의 내구연수 및 잔존수명을 산정하였으며 그 결과를 지방공기업법에서 제시하고 있는 내용연수와 비교하여 분석하였다.

파랑과 해저지반 그리고 해안 해양 구조물과의 상호작용은 지반공학뿐만 아니라 해안공학 분야에서도 중요한 이슈중의 하나이며, 파랑에 의해 해저지반 내부에 발생하는 응력 및 간극수압 거동의 파악은 다양한 해안 해양 구조물의 기초 설계 및 해저 연안 지반의 불안정성 검토에 있어서 중요한 과제이다. 해저지반의 불안정에 대한 문제 중, 파랑에 의한 해저지반의 액상화는 기존의 연구를 통하여, 두개의 메커니즘이 존재한다는 것이 밝혀졌으며, 이는 각각 파랑에 의해 해저지반 내부에 발생하는 과잉간극수압의 변동 특성 및 잔류 특성에 따른 것이다. 본 연구에서는 일본 시코쿠 코치(高知)현에 위치하고 있는 코치항에서 채취한 토사에 대한 동적 특성을 고려하여, 파랑에 의해 해저지반 내부에 발생하는 침투류에 의한 잔류과잉간극수압에 대하여 해석을 하였으며, 더 나아가, 코치항에서 계측된 값과 비교 분석을 하였다.