Hydride reorientation is widely known as one of the major degradation mechanisms in Zirconium cladding during dry storage. Some previous theoretical models for hydride reorientation used assumption of an ideal radial basal pole orientation for HCP structure of Zirconium cladding. Under this assumption, circumferential hydride was considered to precipitate in the basal plane while radial hydride was considered to precipitate in the prismatic plane, thereby giving energetical penalty on thermodynamical precipitation of radial hydrides. However, in reality, reactor-grade Zirconium cladding exhibits average 30° tilted texture, adding complexity to the hydride precipitation mechanism. In this study, reactor-grade Zirconium cladding was charged with hydrogen and hydride reorientation -treated specimens were fabricated. Microstructural characterization of hydrides was conducted via following three methods in terms of interface and stored energy. And this study aimed to compare these characteristics between circumferential and radial hydrides. Using Electron Back Scattered Diffraction (EBSD), the interface was investigated assuming that interface lies parallel to the axial axis of the tube. These were further validated with Transmission Electron Microscope (TEM). In addition, Differential Scanning Calorimetry (DSC) analysis was conducted to calculate the stored energy. This investigation is expected to establish fundamental understanding of how hydrides precipitate in Zirconium cladding with different orientations. And it will also increase the predictability of radial hydride formation and help understanding the mechanical behavior of Zirconium cladding with radial hydrides.

Background: After the coronavirus disease 2019 (COVID-19) pandemic, many changes in education were observed, particularly non-face-to-face classes. Many studies have focused on the suitability of non-face-to-face classes and the satisfaction of both students and teachers with this teaching method. However, no study on the suitability of numerous teaching methods in teaching physical therapy subjects has been conducted. Objectives: To investigated the suitability of three teaching methods, namely, face-to-face, non-face-to-face, and mixed classes, in teaching physical therapy subjects. Design: Survey research. Methods: 336 students studying physical therapy participated. A survey was conducted on the suitability of face-to-face, non-face-to-face, and mixed classes for 16 subjects. The survey was conducted using a Google questionnaire. Results: Face-to-face classes were found to be suitable for teaching the basic fields of physical therapy, and face-to-face and mixed classes were suitable for teaching the principle of diagnostic evaluation. Furthermore, faceto- face classes were found to be suitable for teaching physical therapy interventions. In other subjects, face-to-face classes were suitable for teaching rehabilitation medicine, non-face-to-face classes were suitable for teaching medical terms, and mixed classes were suitable for teaching daily life activities. Conclusion: The results of this study can be used as a basis for choosing the appropriate methods for learning and teaching physical therapy subjects.

Since SMR’s reduced reactor radius results in higher neutron leakage, SMR operates at a relatively lower discharge burnup level than traditional Light Water Reactors (LWRs). It may result in larger spent fuel amounts for SMRs. Furthermore, recent studies demonstrated that NuScale reactor will generate a significantly higher volume of low- and intermediate-level waste owing to components located near the active core including the core barrel and the neutron reflector. For spent nuclear fuel simulation, FRAPCON-4.0 was updated. Major modifications were made for fission and decay gas release, pellet swelling, cladding creep, axial temperature distribution, corrosion, and extended simulation time covering from steady-state to dry storage. In this study, typical 17×17 PWR fuel (60 MWd/kgU) and NuScale Power Module (36 MWd/kgU) was compared. NuFuel-HTP2™ fuel assembly, which has a half-length of proven LWR fuel, was employed. Owing to the lower discharge burnup and operating temperature, the maximum hydrogen pickup was 73 wppm and the maximum hoop stress was ~25 MPa. Therefore, hydride reorientation issue is irrelevant to SMR spent fuel. In this context, the current regulatory limit for dry storage (i.e. 400°C and 90 MPa) can be significantly alleviated for LWR-based SMRs. The increased safety margin for SMR spent fuel may compensate high spent fuel management cost of SMRs incurred by an increased amount. The comprehensive analysis on SMR spent fuel management implications are discussed based on simulated SMR fuel characteristics.

Hydride reorientation is one of the major concerns for cladding integrity during dry storage. In this study, mechanical property of post-reorientation cladding was investigated according to the morphology and amount of the hydrides. Cladding peak temperature limit 400°C was suggested by U.S. NRC in concern of cladding creep and hydride reorientation. In line with this regulatory limit, hydride reorientation was conducted during cool-down process from the maximum temperature of 400°C, using constant internal pressurization method. The specimens were charged for hydrogen from 100 to 1,000 wppm, and various pressures range of 7.5-18.5 MPa were applied. The morphology was examined by optical microscopy. Radial hydride fraction (RHF) and radial hydride continuous path (RHCP) were calculated using image analysis software PROPHET. Finally, strain energy density (SED) was investigated via ring compress tests and the hydrogen concentration was analyzed. The result shows that when RHF is higher than 5%, SED exponentially decreases with RHF. For RHF less than 5%, SED was primarily affected by the total amount of hydrogen. Shortened length of radial hydrides with the presence of circumferential hydrides may block the radial propagation of crack. The result implies that lower burnup spent fuel with lower hydrogen concentration may be more vulnerable in terms of radial hydride compared to higher burnup fuel.

본 연구는 대덕산･금대봉 생태계보전지역 내 분포하는 관속 식물상을 파악하여 식물분포를 밝히고, 향후 대덕산-금대봉 생태계보전지역의 주요 식물에 대한 효율적인 관리와 보전을 위해 수행하였다. 2017년 4월부터 2019년 10월까지 총 14회에 걸쳐 현지조사를 실시하였다. 대덕산-금대봉 생태계보전지역에 자생하는 관속식물상은 83과 245속 372종 4아종 45변종 8품종으로 총 428분류군이 조사되었다(Appendix 1). 이 중 한국특산 식물은 키버들, 참개별꽃, 진범, 갈퀴현호색 등 19분류군이며, 환경부지정 희귀 및 멸종위기 식물은 개병풍, 가시오갈피, 대성 쓴풀, 복주머니란으로 총 4분류군이 조사되었고, 산림청 지정 희귀식물은 19과 34속 34종 2변종 총 36분류군이 나타났다. 침입외래식물은 토끼풀, 달맞이꽃, 지느러미엉겅퀴 등 4과 8속 8종 총 8분류군으로 조사되었으며. 도시화지수(UI)는 2.5%, 귀화율(NI)은 1.9%로 나타났다. 본 조사지역의 양치식물은 7과 9속 7종 2변종으로 총 9분류군이 나타났고, 양치식물계수는 0.52로 나타났다. 대한약전 기준 약용자원식물은 16과 24속 24 종 2변종 1품종 27분류군이 확인되었다. 민속식물은 772과 175 속 216종 28변종 3품종 4아종 251분류군이 확인되었으며, 대덕산‧금대봉에서 출현한 428분류군 중 58.6%가 민속식물로 나타났다. 민속식물을 분류 별로 보면 가장 많은 213분류군이 식용 식물로 분류되었다. 약용식물은 161분류군이었으며, 향신용식물은 11분류군으로 나타났다. 환경부에서 멸종위기 식물로 지정된 대성쓴풀과 복주머니란 등의 희귀식물은 시급히 보호 및 보전에 필요한 대책을 마련해야 할 것으로 판단되며, 나도범의 귀는 북방계식물로 남한 내 자생지가 검룡소 1곳이 보고되고 있어 자생지보호의 필요성이 있을 것으로 판단된다.