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.

원전 해체 공정 중 다량의 콘크리트 방사성 폐기물의 절단 과정에서 불가피하게 방사성 에어로졸이 생성된다. 방사성 에어 로졸은 인체 호흡기 흡착에 의한 내부피폭을 유발하기 때문에 작업자의 방사선 방호를 위한 내부피폭평가가 필수적으로 시행되어야 한다. 그러나 실제 작업환경의 에어로졸 특성값을 사용하기에는 선행 연구가 미비하며 콘크리트에 포함된 방사성 핵종의 수가 많기 때문에 정확한 작업자 내부피폭평가를 위해서는 상당한 시간과 인력이 필요하다. 따라서, 본 연구에서는 사전 연구된 콘크리트 에어로졸 특성값을 활용하여 원전 해체 전 절단 작업자의 내부 피폭량을 빠르게 예측할 수 있는 새로운 방법론을 제시하고자 한다. 본 연구팀은 콘크리트 절단 시 발생하는 사전 연구에서 발표된 에어로졸의 수농도 크기 분포데이터를 뉴턴-랩슨법을 이용하여 피폭평가 계산에 필요한 방사능중앙 공기중역학직경(Activity Median Aerodynamic Diameter)값으로 변환하였다. 또한 원전 정지 10년 후 비방사능 값을 ORIGEN code로 계산하였으며, 최종적으로 핵종별 예 탁유효선량을 IMBA 프로그램을 이용하여 계산하였다. 핵종별 예탁유효선량값을 비교한 결과 152Eu에 의한 최대 예탁유효선량은 전체 선량값의 83.09%를 차지하고, 152Eu를 포함한 상위 5개 원소(152Eu, 154Eu, 60Co, 239Pu, 55Fe)의 경우 최대 99.63%를 차지함을 확인하였다. 따라서 원전 해체 전 콘크리트의 구성 원소 중 상위 5개 주요 원소 측정을 먼저 시행한다면 더 빠르고 원활한 방사능 피폭관리 및 해체 작업 안전성 평가가 가능할 것으로 판단된다.

In the development of advanced ceramic tools, material improvements and design freedom are critical in improving tool performance. However, in the die press molding method, many factors limit tool design and make it difficult to develop innovative advanced tools. Ceramic 3D printing facilitates the production of prototype samples for advanced tool development and the creation of complex tooling products. Furthermore, it is possible to respond to mass production requirements by reflecting the needs of the tool industry, which can be characterized by small quantities of various products. However, many problems remain in ensuring the reliability of ceramic tools for industrial use. In this study, alumina inserts, a representative ceramic tool, was manufactured using the digital light process (DLP), a 3D printing method. Alumina inserts prepared by 3D printing are pressurelessly sintered under the same conditions as coupon-type specimens prepared by press molding. After sintering, a hot isostatic pressing (HIP) treatment is performed to investigate the effects of relative density and microstructure changes on hardness and fracture toughness. Alumina inserts prepared by 3D printing show lower relative densities than coupon specimens prepared by powder molding but indicate similar hardness and higher fracture toughness values.

The consumption of pre-treated vegetables (including fresh-cut vegetables) has been significantly increased because of their ease of use for cooking. Vegetable cutting machine has been widely utilized for producing fresh-cut vegetables or agricultural products with different sizes; however, its design standard is not specifically established depending on types of agricultural products. Therefore, this study was conducted to determine mechanical properties (compressive and shear force) of targeted agricultural products (radish, carrot, squash, cucumber, shiitake mushroom and sweet potato) for developing multipurpose vegetable cutting machine. According to ASAE standard (s368.3), compressive and shear force of targeted agricultural products were measured by using custom built UTM (universal testing machine). Shape type of samples and speed ranges (5~15 mm/min) of loading rate on bioyield and shear points were varied by targeted agricultural products. The range of averaged bioyield points of targeted agricultural products were between 7.89 and 146.98 N. On the other hands, their averaged shear points were from 22.50 to 53.47 N. Results clearly showed that the bioyield and shear points of targeted agricultural products were thoroughly affected by their components. As accumulating compressive and shear points of agricultural products, it can be technical feasible to establish the design standard and control mechanism of multipurpose vegetable cutting machine.