As the decommissioning of domestic nuclear power plants (Gori Unit 1 and Wolseong Unit 1) becomes more visible, many research projects are being conducted to safely and economically decommissioning of domestic nuclear power plants (NPPs). After permanent shutdown, decommissioning of NNPs proceeds through decontamination, cutting of main equipment, waste disposal and site restoration stages. And various technologies are applied at each stage. In particular, remote cutting of neutron induced structures (RV, RVI, etc.) is a technology used in developed countries in the cutting stage, and remote cutting has been evaluated as a core technology for minimizing workers’ radiation exposure. Generally, remote cutting technologies are divided into mechanical/thermal/electrical cutting. Among various thermal cutting technologies, plasma arc cutting (PAC) is more economical and easily to remote control than other cutting technologies, and is also effective in cutting STS304 plates. PAC is a thermal cutting technology that melts the base material at the cutting area with a plasma arc heat source and removes melted material by blowing it out with cutting gas. The cutting quality depends on the stand-off distance and power (current), material thickness, cutting speed, etc., while double arcing will occur if the cutting conditions are not suitable. A monitoring system that can confirm double arcing during remote cutting is necessary because double arcing can reduce cutting quality, increase secondary waste (increase kerf and aerosol), and cause non-cutting. In this study, we used an ultrahigh-speed camera equipped with a band-pass filter to capture clear arc shapes, and measured voltage waveforms with a data acquisition system. We studied a monitoring method that can confirm the occurrence of double arcing by synchronizing the obtained arc shape and voltage waveform, and the effects of double arcing on the STS304 plates. The results of this study are expected to be helpful in the development of the remote cutting process using plasma arc cutting when decommissioning of domestic NPPs.

Kori Unit 1, pressurized water reactor, is the Korea’s first commercial nuclear power plant. It successfully generated electricity for a period of 30 years, commencing from April 19, 1978. Following its approval for continued operation in 2008, Kori Unit 1 continued to operate for an additional 9 years, resulting in a total operational period of 39 years. On June 18, 2017, Kori Unit 1 was permanently shut down. Since then, Korea is actively preparing for the decommissioning of nuclear power plant. During the decommissioning of a nuclear power plant, the heavy components such as reactor, steam generator, pressurizer, reactor coolant pump located in the containment building should be taken out of the containment building. To take out heavy components from the containment building, pipes connected to heavy component should be cut. There are numerous pipes connected to the heavy component, each with varying dimensions and material. Each pipe has a different level of contamination depending on its use. In this study, optimal cutting method of pipe connected to steam generator, one of the heavy components of nuclear power plant, is proposed during the decommissioning of Kori unit 1. In case of pipe connected to Kori unit 1 steam generator, material is stainless steel or carbon steel. These pipes have varying inner diameter, ranging from 0.6 cm to 74 cm, and thickness ranging from 0.15 cm to 7.1 cm. These pipes are classified as low and intermediate level waste (LILW) or very low level waste (VLLW). Because characteristics of pipes are different, each pipe optimal cutting methods are proposed differently considering material, dimension, contamination level, cutting cost, cutting time, and the management of secondary waste. As a result, the cutting method for pipe of reactor coolant system is selected to orbital cutting. The cutting method of main steam pipe and main feedwater pipe is selected to oxygen cutting. In case of other small pipes, cutting method is selected to circular saw.

The dismantling of the reactor pressure vessel has been carried out at a number of commercial nuclear power plants, including the Zion nuclear power plant in the United States and the Stade nuclear power plant in Germany. The dismantling method for the reactor pressure vessel is either in the air or in the water, depending on the utility. In general, a mechanical cutting method is used when dismantling the reactor pressure vessel in the water. And when dismantling a nuclear reactor pressure vessel in the air, the thermal cutting method is applied. However, there is no case of dismantling commercial nuclear reactor pressure vessel by applying a mechanical method in the air. In this study, when a nuclear reactor pressure vessel is dismantled by applying a mechanical method in the air, the applicability was evaluated by testing it using a demonstration mockup of Kori Unit 1. For the evaluation, the mockup was made in the actual size of Kori Unit 1. Mechanical cutting devices used the band saw and the circular saw. In the test, the cutting of the reactor pressure vessel was performed remotely by reflecting the working conditions of the decommissioning site. The band saw cutting method was applied to vertical cutting, and the circular saw cutting method was applied to horizontal cutting. In order to dismantle one cut-off piece, mockup test was performed according to a series of dismantling processes, it consists of preparatory work, vertical cutting process, horizontal cutting process, packaging process and finishing work. The cutting speed of the band saw is 3–10 mm·min−1, and the cutting speed of the circular saw is 2–4 mm·min−1. As a result of the test, when the mechanical cutting method was applied, as is known, the kerf width was smaller than when the thermal cutting method was applied. The cut surface showed a clean state without drag lines generated during thermal cutting. However, the working time was much slower than when the thermal cutting method was applied.

본 연구는 하절기 ‘매향’ 딸기 자묘의 삽목 번식에 적 절한 관수 방법을 구명하기 위해 수행되었다. 딸기 자묘의 삽수는 24구 딸기 전용 포트(24구, 60 × 34 × 10cm) 에 상업용 혼합 상토(Tosilee)를 이용하여 삽목하고, 반 밀폐형 소형비닐터널에 위치시켰다. 각각의 반 밀폐형 소형터널의 처리는 다음과 같이 처리했다; 대조구(무처 리), 두상관수(하루 두 번), 매트관수(하루 두 번), 그리 고 안개관수(8:00시부터 18:00시까지 30분 온/오프 설정). 딸기 자묘는 반 밀폐형 소형터널 내에서 8일 동안 발근을 하였고, 그 이후 플라스틱 필름을 제거 하였다. 삽목 후 61일째에 초장, 근장, 1차 근수, 엽병장, 엽장, 엽폭, 크라운 직경, 엽록소 값, 엽면적, 지상부와 지하부의 생 체중 및 건물중을 측정하였다. 터널 내의 하루 평균 상 대습도는 각각 안개관수, 두상관수, 매트관수, 대조구순 으로 72.5, 56.3, 45.8, 그리고 29%를 나타냈다. 그러나 공기온도는 모든 처리에서 유사하였다. 딸기 자묘의 4일 째와 8일째 발근율은 두상관수와 안개관수 처리에서 유 의적으로 높았다. 초장, 엽병장, 크라운 직경, 엽면적은 두상관수와 안개관수 처리에서 높은 값을 나타냈다. 게다가 지상부의 생체중 및 건물중은 다른 처리에 비해 두상관수와 안개관수 처리에서 무거웠다. 지하부의 건물 중은 안개관수 처리에서 유의적으로 무거웠다. 하지만 근장, 1차 근수, 엽록소 값, 지하부의 생체중은 모든 처 리구에서 유의적인 차이를 나타내지 않았다. 결과적으로, ‘매향’ 딸기의 삽목 번식 시 생육과 발근율은 두상관수 와 안개관수 처리에서 가장 효과적인 것으로 나타났다.

돌나물의 노지 가을삽식을 위하여, 줄기의 삽수 부위(상부, 중부, 하부) 및 삽식 방법(점파, 조파 산파)에 따른 월동전후 생육특성을 조사하였다. 삽수부위에 따른 삽목후 40일째의 월동전 생육은 상부 삽수에서 초장, 근장, 줄기수, 지경수, 지상부 생체중 및 건물중 등에서 유의하게 높았으며, 월동후 개화전(May 10th) 생육은 개체당 줄기수, m2당 지상부 생체중 및 건물중에서 하부 삽수보다 유의한 증가를 보였다. 삽식 방법에 따른 삽목후 40일째의 월동전 생육은 점파(10×10cm)가 조파나 산파보다 양호하였고, m2당 지상부 생체중 및 건물중도 점파〉산파〉조파 순으로 높았다. 월동후 생육(May 10th)은 개체당 줄기수, m2당 생체중 및 건물중에서 점파가 조파보다 유의하게 증가하였다. 돌나물의 가을 노지 삽식은 줄기 상부의 삽수를 이용하는 것이 월동 전후 생육 및 수량성에 유리하였으며, 삽식방법은 점파에서의 수량성이 가장 양호하였으나, 생력화를 위해서는 월동후 생체중에서 점파와 유의한 차이를 보이지 않은 혼파방법이 바람직할 것으로 기대되었다.

This experiments were carried out to determine growth characteristics, dry matter yield and voluntary intake of silage according to growth stage of Sorghumsudangrass(SSH) hybrid in mono-cropping and inter-cropping(C; com, T1; cutting of SSH at milk stage.

Polyacetal resin is usually used to make molds, but it is difficult to achieve dimension accuracy during molding. Therefore it is usually necessary to cut the polyacetal resin after a molding process. Polyacetal resin is easily machining by standard machine tool. Acetal is also a thermal stable material which can be totted without coolant Another concern about the use of polyacetal resin is that it absorbs water easily, which also results in problems with dimension accuracy Therefore, in this study, the cutting resistance of water-absorbed polyacetal resin and its surface roughness after cutting in order to achieve the highest degree of accuracy in the cutting of polyacetal resin were investigated. Also, The Robust Design method uses a mathematical tool called orthogonal arrays to study a large number of decision variables with a small number of experiments. It also uses a new measure of quality, called signal-to-noise (S/N) ratio, to predict the quality from the customer's perspective. Thus, we have taken Taguchi's parameter design approach, specifically orthogonal array, and determined the optimal levels of the selected variables through analysis of the experimental results using S/N ratio.

A study to analyze and solve problems of polyacetal resin cutting experiment has presented in this paper. We have taken Taguchi's parameter design approach, specifically orthogonal array, and determined the optimal levels of the selected variables through analysis of the experimental results using S/H ratio.

The objective of ECMS(Environmentally Conscious Manufacturing Systems) is to consider environmental effects through the entire product life cycle from product development stage to design, manufacturing, supplying, using and disposing stage. Recently, environment-oriented recycling, reusing and manufacturing technologies have been researched actively in every engineering fields. In the field of chemical engineering, HHS(Health Hazard Scores) which classifies and analyzes hazardous materials in production processes has been presented. Metal cutting processes also have a lot of harmful factors, and especially hazardous components in cutting fluids have been known to have a bad effect on workers and working area. However, research works such as HHS have been little accomplished in metal cutting processes. In this research, a environmentally conscious machining process is presented by classifying hazardous components in cutting fluids, by using LCA(Life Cycle Assessments) and HHS method, and by evaluating environmental effects from cutting fluids.

As the first step of study on fabrication of ceramic powders from phytoliths in rice, especially in rice husks, pulverization method of rice husks and the properties of milled rice husks were investigated. Impact methods, such as ball milling, were not meaningful for pulverizing elastic and thin fabric structure of rice husks. The most effective one was cutting method. In the present work, a rotating knife cutting method was applied to pulverizing rice husks. A 40-mesh screen was inserted under the rotating knives. The most portion of the milled powder was found in -50/+100 mesh section. Morphology of the milled rice husks revealed that the husks larger than 70 mesh were flake-like shape, at -70/+100 mesh section relatively equi-axed shape, at -170/+325 mesh section rod-like shape, and below 325 mesh section dust-like shape. Tap density of raw rice husks was about 0.1 , while those of milled rice husks were over . This meant that, for a given volume of reactor, raw material charge can be increased more that 4 times when using milled rice husks than unmilled one. True densities of unmilled and milled rice husks were higher than , and increased with decreasing milled sizes.

This field experiment was undertaken to find out the effect of grazing and cutting management on the forage quality and soil hardness at different legumes sown swards of the experimental field of Livestock Experiment Station in Suweon, from August 1985 to

This field experiment was conducted to determine the effect of grazing and cutting management on the forage production and botanical composition at different legumes sown swards of the experimental field of Livestock Experiment Station. in Suweon, from Au

본 연구는 희귀 식물인 거문도닥나무를 대상으로 종자 및 삽목번식을 통하여 효율적인 번식방법을 규명하고자 하였다. 실험 결과 종자번식은 실내, 실생 번식 모두 발아율에서 유의성이 나타났다. 저장 종자는 저온 습윤의 경우 항온 20℃ 효과를 보였으며, 변온 처리에서는 발아율이 대체적으로 낮게 나타나 종자 번식에서 거문도닥나무는 습윤 저장 후 항온 20℃에서 발아율 이 높았으며, 실생 번식은 노천매장에서 종자를 번식하는 것이 가장 효과적인 것으로 실험에서 확인되었다. 삽목번식의 관수 시설에 따라 캘러스 형성, 뿌리 수 등 발근율을 확인한 결과 미 스트 관수 비닐하우스에서 녹지의 중간, 아랫부분에서 10.0%가 발근 하였고, 숙지 삽목은 모두 발근 하지 않았다. 특히, 뿌리 수와 뿌리 길이가 각각 5개, 112.6 ㎜로 미스트 관수 비닐하우스에서 월등히 높은 결과를 보여 거문도닥나무 삽목은 습도에 영향을 미치는 것을 알 수 있었다. 전처리에 따른 녹지 삽목은 미스트 관수 비닐하우스에서 거문도닥나무의 중간 부분, 아랫부분을 대상으로 삽목을 실험한 결과 캘러스 형성률, 발근율, 뿌리 수, 뿌리 길이 모두 유의성이 있었다. 녹지 삽목은 평균 발근 율이 23.7%로 저조하였으며, IBA 500 ppm, IBA 1000 ppm, NAA 2000 ppm에서 발근 좋은 것으로 나타났다. 이에, 녹지 삽목의 아랫부분보다 중간 부분이 삽목번식에 효과가 있는 것으 로 실험에서 확인되었다. 특히, 숙지 삽목은 평균 발근율이 11.9%로 녹지 삽목에 비해 저조하였는데 이는 숙지 부분의 잎이 거의 없으며, 잎이 있는 때는 조기에 떨어져 삽목에 영향을 준 것으로 판단된다.

눈향나무(Juniperus chinensis var. sargentii Henry)는 누워서 자라는 상록침엽관목으로 수고 60 cm까지 성장한다. 지리적으로는 동북아시아에 한정되어 분포하는 수종이며, 우리나라에서는 고산지대의 산정부근에서만 극히 일부 자생하여 멸종의 위기에 직면하고 있는 위기종(Endangered species)으로 지정되어 보호되고 있다. 본 연구는 희귀수종 눈향나무의 유전자원보존을 위한 삽목증식법을 개발하기 위하여 삽목시기 및 발근촉진제의 종류별 농도에 따른 발근특성을 조사하였다. 삽목 발근율은 삽목시기와 발근촉진제의 종류 및 농도에서 각각 고도의 유의성이 인정되었다. 삽목은 8월보다 5월이 적정한 시기로 판단되었으며, 발근율과 발근특성을 고려한 발근촉진제의 종류 및 농도는 IBA 1000 mgL-1 처리하는 것이 발근율 36.4%(무처리 30.4%)로 캘러스 형성율이 높고 발근이 촉진되는 것으로 나타났다. 삽수의 발근에 따른 뿌리의 수, 길이 및 굵기에 대한 특성에서는 모두 발근촉진제의 종류 및 농도에 따른 통계적인 유의성이 인정되지 않았다.