• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 2005년도 춘계학술발표회
• /
• pp.107-108
• /
• 2005

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 2005년도 추계학술발표회
• /
• pp.562-563
• /
• 2005

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1998년도 추계학술발표회요약집
• /
• pp.269-269
• /
• 1998

• Nuclear Engineering and Technology
• /
• 제41권10호
• /
• pp.1347-1360
• /
• 2009

A multi-dimensional component for the thermal-hydraulic system analysis code, MARS, was developed for a more realistic three-dimensional analysis of nuclear systems. A three-dimensional and two-fluid model for a two-phase flow in Cartesian and cylindrical coordinates was employed. The governing equations and physical constitutive relationships were extended from those of a one-dimensional version. The numerical solution method adopted a semi-implicit and finite-difference method based on a staggered-grid mesh and a donor-cell scheme. The relevant length scale was very coarse compared to commercial computational fluid dynamics tools. Thus a simple Prandtl's mixing length turbulence model was applied to interpret the turbulent induced momentum and energy diffusivity. Non drag interfacial forces were not considered as in the general nuclear system codes. Several conceptual cases with analytic solutions were chosen and analyzed to assess the fundamental terms. RPI air-water and UPTF 7 tests were simulated and compared to the experimental data. The simulation results for the RPI air-water two-phase flow experiment showed good agreement with the measured void fraction. The simulation results for the UPTF downcomer test 7 were compared to the experiment data and the results from other multi-dimensional system codes for the ECC delivery flow.

• Nuclear Engineering and Technology
• /
• 제46권6호
• /
• pp.725-736
• /
• 2014

It is very important to detect and identify small anomalies and component failures for the safe operation of complex and large-scale artifacts such as nuclear power plants. Each diagnostic technique has its own advantages and limitations. These facts inspire us not only to enhance the capability of diagnostic techniques but also to integrate the results of diagnostic subsystems in order to obtain more accurate diagnostic results. The article describes the outline of four diagnostic techniques developed for the condition monitoring of the fast breeder reactor "Monju". The techniques are (1) estimation technique of important state variables based on a physical model of the component, (2) a state identification technique by non-linear discrimination function applying SVM (Support Vector Machine), (3) a diagnostic technique applying WT (Wavelet Transformation) to detect changes in the characteristics of measurement signals, and (4) a state identification technique effectively using past cases. In addition, a hybrid diagnostic system in which a final diagnostic result is given by integrating the results from subsystems is introduced, where two sets of values called confidence values and trust values are used. A technique to determine the trust value is investigated under the condition that the confidence value is determined by each subsystem.

• Nuclear Engineering and Technology
• /
• 제37권6호
• /
• pp.511-524
• /
• 2005

Thermalhydraulic reactor simulation of tomorrow will require a new generation of codes combining at least three scales, the CFD scale in open medium, the component scale and the system scale. DNS will be used as a support for modelling more macroscopic models. NEPTUNE is such a new generation multi-scale platform developed jointly by CEA-DEN and EDF-R&D and also supported by IRSN and FRAMATOME-ANP. The major steps towards the next generation lie in new physical models and improved numerical methods. This paper presents the advances obtained so far in physical modelling for each scale. Macroscopic models of system and component scales include multi-field modelling, transport of interfacial area, and turbulence modelling. Two-phase CFD or CMFD was first applied to boiling bubbly flow for departure from nucleate boiling investigations and to stratified flow for pressurised thermal shock investigations. The main challenges of the project are presented, some selected results are shown for each scale, and the perspectives for future are also drawn. Direct Numerical Simulation tools with Interface Tracking Techniques are also developed for even smaller scale investigations leading to a better understanding of basic physical processes and allowing the development of closure relations for macroscopic and CFD models.

• Nuclear Engineering and Technology
• /
• 제55권3호
• /
• pp.827-838
• /
• 2023

Centrifugal pump is a key part of nuclear power plant systems, and its health status is critical to the safety and reliability of nuclear power plants. Therefore, fault diagnosis is required for centrifugal pump. Traditional fault diagnosis methods have difficulty extracting fault features from nonlinear and non-stationary signals, resulting in low diagnostic accuracy. In this paper, a new fault diagnosis method is proposed based on the improved particle swarm optimization (IPSO) algorithm-based variational modal decomposition (VMD) and relevance vector machine (RVM). Firstly, a simulation test bench for rotor faults is built, in which vibration displacement signals of the rotor are also collected by eddy current sensors. Then, the improved particle swarm algorithm is used to optimize the VMD to achieve adaptive decomposition of vibration displacement signals. Meanwhile, a screening criterion based on the minimum Kullback-Leibler (K-L) divergence value is established to extract the primary intrinsic modal function (IMF) component. Eventually, the factors are obtained from the primary IMF component to form a fault feature vector, and fault patterns are recognized using the RVM model. The results show that the extraction of the fault information and fault diagnosis classification have been improved, and the average accuracy could reach 97.87%.

• 한국지진공학회논문집
• /
• 제28권3호
• /
• pp.141-147
• /
• 2024

Earthquakes of magnitude 3.0 or greater occur in Korea about 10 times on average yearly, and the number of earthquakes occurring in Korea is increasing. As many earthquakes have recently occurred, interest in the safety of nuclear power plants has increased. Nuclear power plants are equipped with many cabinet-type control facilities to regulate safety facilities, and function maintenance is required during an earthquake. The seismic performance of the cabinet is divided into structural and functional performances. Structural performance can be secured during the design procedure. Functional performance depends on the vibration performance of the component. Therefore, it is necessary to confirm the seismic performance of the components. Generally, seismic performance is confirmed through seismic simulation tests. When checking seismic performance through seismic simulation tests, it is difficult to determine the effect of frequency and maximum acceleration on an element. In this paper, shaking table tests were performed using various frequencies and various maximum accelerations. The seismic performance characteristics of the functions of electrical equipment components were confirmed through tests.

• 방사성폐기물학회지
• /
• 제3권3호
• /
• pp.237-247
• /
• 2005

방사능에 오염된 시설물의 해체 작업은 예측할 수 없는 방사능의 출현으로 항상 사고의 위험성에 노출되어 있어 계획했던 해체 일정이 변경되어야 하고, 전체 공정의 재설계가 다시 수행되어야 하는 비경제적인 작업이 수없이 반복되고 있다. 해체 디지털 목업 시스템 설계에 필요한 구성인자들을 검토하였다. 조사된 단위 구성요소들은 해체 데이터베이스 시스템, 연구로 시설과 제염 및 해체 장비 모델링 시스템, 방사능 오염 분포도를 제작하는 3차원 방사화 매핑, 그리고 해체 일정을 평가하는데 기초가 되는 단위 작업별 평가식과 가중치 값 등이 있다. 독립적으로 운영되는 이들 구성 요인들을 통합된 시스템으로 만들기 위해 단위 시스템들에 대한 아키텍쳐 구현 연구가 수행되었다. 연구 결과 해체 디지털 목업 시스템을 통합된 환경에서 다양한 시나리오를 시험 평가할 수 있도록 하기위해 연구로 시설의 제염 및 해체 활동을 시각적으로 보여줄 수 있는 가시화(visualization) 모듈과 해체 일정 및 해체 비용을 평가 및 분석하는 시뮬레이션(simulation) 모듈로 구분하여 소프트웨어 아키텍쳐를 구현하였다.

• Reproductive and Developmental Biology
• /
• 제32권3호
• /
• pp.147-152
• /
• 2008

The aim of this study was to investigate what components of porcine epididymal fluid (pEF) influences the nuclear maturation of porcine germinal vesicle oocytes. Porcine cumulus-oocytes complexes from follicles were cultured in TCM 199 containing pEF. After 48 h cultures, oocytes were examined for evidence of GV breakdown, metaphase I, anaphase-telophase I, and metaphase II. Maturation rate of oocytes was significantly increased in media supplemented with 10% pEF during in vitro maturation (IVM) than in those without pEF. When lipid component of pEF was removed by treating n-heptane, no significant difference was observed in maturation of oocytes between n-heptane treatrment and intact pEF group. However, the proportion of oocytes reaching at metaphase II (M II) was significantly (p<0.05) decreased in the oocytes cultured in media containing trypsin-treated pEF compared to those in media with intact pEF. When porcine GV oocytes were matured in the medium supplemented with intact pEF or pEF heated at $56^{\circ}C$ and $97^{\circ}C$, rates of oocytes remained at GV stage were 11.7%, 29.4% and 42.0%, respectively. However, there were no difference in proportion of oocytes reaching at MII stage among intact pEF group and $56^{\circ}C$ group. Present study suggests that 1) pEF contains an enhancing component(s) for nuclear maturation in vitro of oocytes, 2) protein(s) of pEF may be capable to promote nuclear maturation in vitro, and 3) enhancing component for nuclear maturation may consist of two factors, which are responsible for germinal vesicle breakdown (GVBD) and promotion of MII stage.