저장조에 위치한 사용후핵연료는 가혹한 원자로 조건에 의해 구조적 건전성이 와해되므로 외력에 취약하다. 따라서 운반 및 취급 중 사고 상황이 고려되어야 한다. 극단적인 경우, 핵연료 취급 중 사고로 인해 핵연료 저장조에서 핵연료집합체 낙하 가 발생할 수 있다. 이러한 사고 상황 하에서 연료봉 파손 등을 평가하기 위해서 수조에 충돌할 때 발생하는 충돌력을 분석 할 필요가 있다. 이는 핵연료가 수조 바닥에 충돌할 때의 속도를 입력으로 하여 평가될 수 있다. 연료봉이 핵연료 중량 및 부 피의 대부분을 차지하고 있으므로, 연료봉 다발은 수중 항력을 예측하는데 중요한 역할을 한다고 볼 수 있다. 본 연구에서는 3×3 의 짧은 연료봉 다발을 모델로 사용하여 수중에서 낙하할 때 받는 수력을 계산하였고, 이를 전산모사와의 비교를 통하 여 검증하였다. 본 방법론을 사용후핵연료 건전성 평가에 적용할 수 있을 것으로 기대된다.

This work investigated the decomposition of aqueous anatoxin-a originated from cyanobacteria using an underwater dielectric barrier discharge plasma system based on a porous ceramic tube and an alternating current (AC) high voltage. Plasmatic gas generated inside the porous ceramic tube was uniformly dispersed in the form of numerous bubbles into the aqueous solution through the micro-pores of the ceramic tube, which allowed an effective contact between the plasmatic gas and the aqueous anatoxin-a solution. Effect of applied voltage, treatment time and the coexistence of nutrients such as NO3 -, H2PO4 - and glucose on the decomposition of anatoxin-a was examined. Chemical analyses of the plasma-treated anatoxin-a solution using liquid chromatography-mass spectrometry (LC-MS) and ion chromatography (IC) were performed to elucidate the mineralization mechanisms. Increasing the voltage improved the anatoxin-a decomposition efficiency due to the increased discharge power, but the energy required to remove a given amount of anatoxin-a was similar, regardless of the voltage. At an applied voltage of 17.2 kV (oxygen flow rate: 1.0 L min-1), anatoxin-a at an initial concentration of 1 mg L-1 (volume: 0.5 L) was successfully treated within 3 min. The chemical analyses using LC-MS and IC suggested that the intermediates with molecular weights of 123~161 produced by the attack of plasma-induced reactive species on anatoxin-a molecule were further oxidized to stable compounds such as acetic acid, formic acid and oxalic acid.

질산성질소는 자연계의 질소 순환과정에서 발생되며, 수중에서는 질산성질소가 무기이온인 질산염(NO3 - )의 형태로 존재한다. 질산성질소는 과도한 질소비료시비나 동물의 분뇨에 의해 오염된 지하수에 존재하며, 인체에 노출 시 암과 같은 질병 유발 가능성을 높인다. 본 연구에서는 흡착등온식 및 흡착속도식 모델을 이용하여 질산염 농도 및 시간에 따른 키토산 비드의 수중 질산염 흡착특성을 평가하였다. 질산염의 농도에 따른 흡착실험에서 Langmuir와 Freundlich 식을 이용하여 최대흡착량 및 흡착형태를 산출한 결과, 키토산 비드의 질산염 흡착형태는 Langmuir식에 가장 일치되 는 경향을 보였으며, 이때 키토산 비드의 질산염 최대흡착량은 14.83 mg 질산염/g 키토산비드이었다. 질산염의 시간에 따른 흡착실험에서 1차속도식 및 2차속도식을 이용하여 질산염의 흡착속도 및 확산형태를 평가한 결과, 키토산 비드 의 초기 흡착속도는 외부확산에 의한1차속도식 경향을 보였으며, 일정시간이 지난 후에는 내부확산에 의한 2차속도식 형태의 경향을 보였다. 본 연구에서 수행한 흡착 모델에 따른 수중질산염의 제거 연구는 키토산 비드의 흡착 형태 및 질산염 제거량을 수학적으로 예측하는데 도움이 된다.

This study was carried out for characterization of MIO synthesized in our laboratory by co-precipitation method and applied isotherm and kinetic models for adsorption properties. XRD analysis were conducted to find crystal structure of synthesized MIO. Further SEM and XPS analysis was performed before and after phosphate adsorption, and BET analysis for surface characterization. Phosphate stock solution was prepared by KH2PO4 for characterization of phosphate adsorption, and batch experiment was conducted using 50 ml conical tube. Langmuir and Freundlich models were applied based on adsorption equilibrium test of MIO by initial phosphate solution. Pseudo first order and pseudo second order models were applied for interpretation of kinetic model by temperature. Surface area and pore size of MIO were found 89.6 m2/g and 16 nm respectively. And, the determination coefficient (R2) value of Langmuir model was 0.9779, which was comparatively higher than that of Freundlich isotherm model 0.9340.

Jinhae Bay located in the southern of Korean Peninsular is an important spawning area in Korea. By some preliminary studies it was measured several times that adult Pacific codes (Gadus microcephalus) were passed (swimming layer: 15 to 18 m) over a submerged sea tunnel (sea bottom: about 30 m) rather than another immigration route when the Pacific codes were tagged surgically with an acoustic transmitters and released inside of the Bay. There is a possibility that the Pacific codes and the other fishes use the route on the sea tunnel as an immigration route are affected by a human–generated underwater noise around the sea tunnel due to the sea tunnel traffic. On this study the 25–hour measurements of the underwater noise level by water layer were conducted with a hydrophone attached on a portable CTD and an underwater noise level meter during four seasons, and the acoustical characteristics of the underwater noise was analyzed. The mean traffic volume for one hour at the sea tunnel on the spring was shown the largest value of 1,408 [standard deviation (SD): 855] vehicles among four seasons measurement. The next one was ordered on the autumn [1,145 (SD: 764)], winter [947 (SD: 598)] and summer [931 (SD: 558)] vehicles. Small size vehicle was formed 84.3% of the traffic volume, and ultra–small size, medium size, large size and extra–large size of the vehicle were taken possession of 8.7%, 3.2%, 2.0% and 1.8%, respectively. On the daily change of the noise level in vertical during four seasons the noise level of 5 m–layer was shown the highest value of 121.2 (SD: 3.6) dB (re 1 μPa), the next one was 10 m– layer [120.7 (SD: 3.5)], 2 m– and 15 m–layer [120.3 (SD: 3.5 to 3.7)] and 1 m–layer [119.2 (SD: 3.6)] dB (re 1 μPa). In relation with the seasonal change of the noise level the average noise level measured during autumn was shown the highest value of 123.9 (SD: 2.6) dB (re 1 μPa), the next was during summer [121.4 (SD: 3.2)], spring [118.0 (SD: 3.4)] and winter [116.5 (SD: 5.1)] dB (re 1 μPa). In results of eigenray computation when the real bathymetry data (complicate shape of sea bed) was applied the average number of eigenray was 2.68 times (eigenrays: 11.03 rays) higher than those of model bathymetry (flat and slightly sloped sea bottom). When the real bathymetric data toward inside (water depth becomes shallow according to a distance between the source of noise and hydrophone) of the Bay was applied on the eigenrays calculation the number of the eigenray was 1.31 times (eigenrays: 12.49 rays) larger than the real bathymetric data toward outside (water depth becomes deep with respect to the distance). But whenthe model bathymetric data toward inside of the Bay was applied the number of the eigenray was 1.05 times (eigenrays: 4.21 rays) larger than the model bathymetric data toward outside.

The aim of this study is to find out the behavior and acoustic backscattering of the large jellyfish Nemopliema nomurai using hydroacoustics in situ. N. nomurai was distributed at depths ranging from 10~15 m during the day. Regarding the behavior of N. nomurai, there was no significant change in depth, and 3D tortuosity was not high. The vertical direction was ±10° from the horizontal, and moving speed was 0.9~1.5 m s–1.With regard to hydro–acoustical characteristics, the mean TS of N. nomurai ranged from –69.6~–56.0 dB at 38 kHz and –69.4~–54.5 dB at 120 kHz. TS variation (Max TS–Min TS) at 38 and 120 kHz was 0~10.2 dB and 0.2~16.0 dB, respectively. Mean TS and TS variation (Max TS–Min TS) of N. nomurai were higher at 120 kHz than at 38 kHz. The results showed that the use of hydroacoustics was effective in estimating the distribution depth, behavior, and acoustic characteristics of the target.

낙동강 상류에 설치된 수중보 2곳(St.1, St.2)과 본류에 설치된 낙단보(St.3) 및 상주보(St.4)의 저서성대형무척추동물 군집구조와 군집안정성을 분석하였다. 조사는 2014년 봄, 여름, 가을 총 3회 수질조사와 병행하여 실시하였다. 분류군별 출현현황은 소형 수중보(St.1, St.2)와 대형 보(St.3, St.4)에서 각각 총 11목 32종, 14목 52종, 13목 34종, 9목 18종이 출현하였다. 군집지수 분석결과, 평균 다양도지수(Hˊ)와 풍부도지수(Rˊ)는 St.2에서 각각 2.65와 2.54로 가장 높았으며, 평균 우점도지수(DI)는 St.4(0.84)에서 가장 높게 나타났다. 섭식기능군(FFG) 분석결과, P(Predator)와 GC(Gathering Collector)의 종수 점유율은 대형보에서 88.0%~90.0%, 수중보에서 64.3%~83.3%로 나타났다. 서식기능군(FHG) 분석결과, 비교적 유수역을 선호하는 종으로 구성된 CL(Clinger)의 점유율이 소형 수중보에서는 32.3%~48.4%로 대형보의 9.7%~25.8% 보다 더 높게 나타났다. 군집안정성 분석결과, 대형 보에서 I 그룹(저항력↑, 회복력↑)과 III 그룹(저항력↓, 회복력↓)에 속하는 종들이 수중보에 비해 각각 더 높은 점유율(75.0% > 70.0%, 16.7% > 14.0%)을 나타냈다. 이화학적 수질요인과의 상관관계를 분석한 결과, 종수 및 개체수는 물리적 환경요인인 pebble입자와 양의 상관성(p<0.05)을 나타냈다. 또한 전기전도도, COD가 종수, 그리고 DO가 개체수와 음의 상관성(p<0.05)을 나타냈다.

본 연구는 통상 muntz metal로 불리는 구리와 아연의 합금 금속의 산화 환원 반응을 이용한 폐수 중 탈인 처리에 관한 연구이다. 연구를 위하여 200 ㎛ 두께의 극세사 형태로 제조된 구리 아연 금 속합금이 수용액 중에서 산화 환원 반응 작용으로 인하여 발생하는 OH radical을 이용하여 금속과 phosphate의 공침 반응에 의해 탈인 처리되는 원리를 이용한 인 처리법에 관한 연구이다. 인 제거 효율은 장시간의 순환 처리보다는 1회 처리에서 가장 제거 효율이 높았으며, 1시간 이후의 순환처리에서는 더 이 상의 제거효율을 보이지 않았다. 이는 금속합금 물질은 표면적이 넓어서 1회 처리만으로도 수용액의 pH 를 평형에 도달하게 하여 반응 효율이 높은 것으로 나타났다. 제조한 합성폐수의 pH 조건은 pH 5 에서 pH 9 사이이며, pH 8일 때 제거 효율이 가장 높았으며 pH 8 이상에서는 효율 증가를 보이지 않았다. 이때 인산염은 H2PO4 -, HPO4 2-의 형태로 가장 많이 존재하는 것으로 조사되었으며, 온도에 따른 인 제 거는 온도만의 영향이 아닌 타 영향인자와의 관계를 고려해야 하며 본 연구에서는 온도가 낮을수록 높은 인 제거 효율을 보였다.

The worldwide abundance of various jellyfish appears to have increased in coastal ecosystems in recent years. The enormous jellyfish blooms cause a variety of problems for the local ecology, fisheries, and aquatic-sports in coastal locations. In this study, jellyfish sting protection net was installed to ensure the safety and reduction of the inflow into the Haeundae beach. In order to confirm the stability of the protection net, the tension for protection net was measured from variation of current speed. The periods for maximum tension were observed correspond to the periods of maximum current speed. The maximum tension for protection net was measured up to 4,100 kg. From field evaluations, the jellyfish sting protection net has demonstrated to stability from the current and tide in the Haeundae beach.

The heat treatment machine based on immersion was developed to reduce temperature difference during netting process and appraised it performance compared current heat treatment machine using high pressure. It was also reviewed the optimum heat treatment procedures for PBSAT monofilament net in accordance with the immersion time and temperature. The procedure was based on physical measurement such as breaking load, elongation and angle of the mesh for PBSAT monofilament. The water temperature gap of the treatment machine based on immersion was less than 1°C. and the energy consumption was also increased in high temperature condition. It was identified that the optimum temperature was 75°C and its optimum processing time was between 15 minutes and 20 minutes to get qualified physical properties.

Visual census and hydro-acoustic survey was carried out at Ulju small scale marine ranching area (MRA) to estimate demersal fish aggregations on September and November 2013. In this hydro-acoustic survey, the authors combined an image sonar with a scientific echo sounder to monitor an underwater situation and compare two acoustic data. Consequently, visual census survey was useful to estimate fish species composition for hydro-acoustic survey, because it is easy to identify aggregated fish species and overcome limits on a fishing depth and ability of an conventional fishing gear like a bottom gill-net or a fish trap at marine ranching area. Mean fish density was estimated as 0.757 g/m2 on September and 0.219 g/m2 on November and Fish abundance was finally calculated as 1.51ton (coefficient of variation, CV=13.1%) on September and 0.44ton (CV=47.7%) on November, respectively. Hydro-acoustic survey combined with the image sonar was useful to monitor fish aggregations and estimate fish stocks around artificial reefs at shallow coastal MRA. We were able to easily identify the underwater structures like an artificial reef and a fishing rope as well as fish aggregations from image sonar data. Therefore, the method was effective to separate unwanted echo signals in acoustic data of scientific echo sounder.

This study is aimed to analyze the three-dimensional underwater irradiance using an optical simulation software and to clarify the propriety and operation method under considering luminous intensity distribution of the luring lamp and penetrability in the seawater, when we use the light diffuser type 300W high powered LED and the metal halide lamp (MHL) on a coastal squid jigging vessel in the 10-ton class, simultaneously. For their attenuation characteristics of each wavelength in relation to the sea, LED lamp was to be effective in the 1.9-fold at 50 m depth and 2.1-fold at 80 m for underwater irradiance more than MHL according to the power consumption. In addition, the underwater irradiance distribution using the LED and MHL combination was rather increased even when reducing total power usage up to 20% depending on the simulation with changing the configuration and lighting angle of the lamp. These results can be utilized as an evaluation method of the operation and performance of the LED lamp according to adjusting its arrangement and lighting angle.

본 논문에서는 해중터널와 수중운항체의 충돌거동을 파악하기 위하여 두 구조체를 모델링하고 해석을 수행하였다. 충돌이 일어나는 해중터널은 원통형으로 단면을 가정하고 콘크리트와 라이닝강판을 가진 구조로 가정하였다. 충돌부위를 제외한 인접부분은 탄성거동을 하는 보요소로 모델링하고 계류라인은 장력을 받는 케이블로 모델링하였다. 수중운항체는 1800톤급 잠수함을 가정하였으며 수리동역학적 부가질량을 고려하여 충돌질량을 산정하였다. 해중터널에 작용하는 부력은 동적완화방법을 사용하여 초기조건에 포함시켰다. 부력비의 변화와 충돌속도의 변화를 고려하여 충돌해석을 수행한 결과, 충돌에너지의 소산은 주로 해중터널에서 발생하고 수중운항체에 의한 에너지 소산은 미미한 것으로 나타났다. 또한 계류라인의 장력과 부력비의 변화에 따라 해중터널의 충돌거동은 큰 영향을 받았다. 특히 충돌력은 기존의 설계기준의 선박충돌력과는 상이한 경향을 보이는 것으로 나타났다.