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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Nuclear Engineering and Technology
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Journal DOI :
Korean Nuclear Society
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Volume & Issues
Volume 33, Issue 6 - Dec 2001
Volume 33, Issue 5 - Oct 2001
Volume 33, Issue 4 - Aug 2001
Volume 33, Issue 3 - Jun 2001
Volume 33, Issue 2 - Apr 2001
Volume 33, Issue 1 - Feb 2001
Selecting the target year
An Input Feature Selection Method Applied to Fuzzy Neural Networks for Signal Estimation
Na, Man-Gyun ; Sim, Young-Rok ;
Nuclear Engineering and Technology, volume 33, issue 5, 2001, Pages 457~467
It is well known that the performance of a fuzzy neural network strongly depends on the input features selected for its training. In its applications to sensor signal estimation, there are a large number of input variables related with an output As the number of input variables increases, the training time of fuzzy neural networks required increases exponentially. Thus, it is essential to reduce the number of inputs to a fuzzy neural network and to select the optimum number of mutually independent inputs that are able to clearly define the input-output mapping. In this work, principal component analysis (PCA), genetic algorithms (CA) and probability theory are combined to select new important input features. A proposed feature selection method is applied to the signal estimation of the steam generator water level, the hot-leg flowrate, the pressurizer water level and the pressurizer pressure sensors in pressurized water reactors and compared with other input feature selection methods.
An Assessment on the Containment Integrity of Korean Standard Nuclear Power Plants Against Direct Containment Heating Loads
Seo, Kyung-Woo ; Kim, Moo-Hwan ; Lee, Byung-Chul ; Jeun, Gyoo-Dong ;
Nuclear Engineering and Technology, volume 33, issue 5, 2001, Pages 468~482
As a process of Direct Containment Heating (DCH) issue resolution for Korean Standard Nuclear Power Plants (KSNPs), a containment load/strength assessment with two different approaches, the probabilistic and the deterministic, was performed with all plant-specific and phenomena-specific data. In case of the probabilistic approach, the framework developed to support the Zion DCH study, Two-Cell Equilibrium (TCE) coupled with Latin Hypercubic Sampling (LHS), provided a very efficient tool to resolve DCH issue. In case of the deterministic approach, the evaluation methodology using the sophisticated mechanistic computer code, CONTAIN 2.0 was developed, based on findings from DCH-related experiments or analyses. For three bounding scenarios designated as Scenarios V, Va, and VI, the calculation results of TCE/LHS and CONTAIN 2.0 with the conservatism or typical estimation for uncertain parameters, showed that the containment failure resulted from DCH loads was not likely to occur. To verify that these two approaches might be conservative , the containment loads resulting from typical high-pressure accident scenarios (SBO and SBLOCA) for KSNPs were also predicted. The CONTAIN 2.0 calculations with boundary and initial conditions from the MAAP4 predictions, including the sensitivity calculations for DCH phenomenological parameters, have confirmed that the predicted containment pressure and temperature were much below those from these two approaches, and, therefore, DCH issue for KSNPS might be not a problem.
A Neuro-Fuzzy Inference System for Sensor Failure Detection Using Wavelet Denoising, PCA and SPRT
Na, Man-Gyun ;
Nuclear Engineering and Technology, volume 33, issue 5, 2001, Pages 483~497
In this work, a neuro-fuzzy inference system combined with the wavelet denoising, PCA (principal component analysis) and SPRT (sequential probability ratio test) methods is developed to detect the relevant sensor failure using other sensor signals. The wavelet denoising technique is applied to remove noise components in input signals into the neuro-fuzzy system The PCA is used to reduce the dimension of an input space without losing a significant amount of information. The PCA makes easy the selection of the input signals into the neuro-fuzzy system. Also, a lower dimensional input space usually reduces the time necessary to train a neuro-fuzzy system. The parameters of the neuro-fuzzy inference system which estimates the relevant sensor signal are optimized by a genetic algorithm and a least-squares algorithm. The residuals between the estimated signals and the measured signals are used to detect whether the sensors are failed or not. The SPRT is used in this failure detection algorithm. The proposed sensor-monitoring algorithm was verified through applications to the pressurizer water level and the hot-leg flowrate sensors in pressurized water reactors.
Pressure-Temperature Limit Curve of Reactor Vessel by ASME Code Section III and Section XI
M.J. Jhung ; Kim, S.H. ; Lee, T.J. ;
Nuclear Engineering and Technology, volume 33, issue 5, 2001, Pages 498~513
Performed here is a comparative assessment study for the generation of the pressure- temperature (P/T) limit curve of the reactor vessel. Using the cooling or heating rate and vessel material properties, the stress distribution is obtained to calculate stress intensity factors, which are compared with the material fracture toughness to determine the relations between operating pressure and temperature during cool-down and heat-up. P/T limit curves are generated with respect to crack direction, clad thickness, toughness curve, cooling or heating rate and neutron fluence, and their results are compared.
Study on the Improvement of Indirect Intra-Oral Dental Digital X-ray Image Sensor with Optical Coupling
Whang, Joo-Ho ; Chung, Jin-Bum ; Kim, Tae-Woo ;
Nuclear Engineering and Technology, volume 33, issue 5, 2001, Pages 514~525
Optimum characteristics of digital X-ray sensor components were analyzed to develop intra- oral dental digital X-ray image sensor using indirect method. Parametric analysis was carried out to optimize the phosphor thickness and the fiber optic plate (FOP) coupling to charge coupled device (CCD). X-ray absorption and light diffusion in the phosphor layer were analyzed by the Monte Carlo method. Real time X-ray image was obtained with prototype X- ray image sensor using general CCD camera with 1∼10 Ip/mm resolution. It has been previously shown that large resolution degradation in X-ray images was caused by miss alignment of FOP to CCD and optical adhesive selection. In this study, we reported that X-ray image quality was greatly improved by using optimized characteristics of alignment device and phosphor thickness.
Fatigue Crack Growth Characteristics of the Pressure Vessel Steel SA 508 Cl. 3 in Various Environments
Lee, S. G. ; Kim, I. S. ; Park, Y. S. ; Kim, J. W. ; Park, C. Y. ;
Nuclear Engineering and Technology, volume 33, issue 5, 2001, Pages 526~538
Fatigue tests in air and in room temperature water were performed to obtain comparable data and stable crack measuring conditions. In air environment, fatigue crack growth rate was increased with increasing temperature due to an increase in crack tip oxidation rate. In room temperature water, the fatigue crack growth rate was faster than in air and crack path varied on loading conditions. In simulated light water reactor (LWR) conditions, there was little environmental effect on the fatigue crack growth rate (FCGR) at low dissolved oxygen or at high loading frequency conditions. While the FCGR was enhanced at high oxygen condition, and the enhancement of crack growth rate increased as loading frequency decreased to a critical value. In fractography, environmentally assisted cracks, such as semi-cleavage and secondary intergranular crack, were found near sulfide inclusions only at high dissolved oxygen and low loading frequency condition. The high crack growth rate was related to environmentally assisted crack. These results indicated that environmentally assisted crack could be formed by the Electrochemical effect in specific loading condition.
Development of Reference Scenarios Based on FEPs and Interaction Matrix for the Near-surface LILW Repository
Lee, Dong-Won ; Kim, Chang-Lak ; Park, Joo-Wan ;
Nuclear Engineering and Technology, volume 33, issue 5, 2001, Pages 539~546
Systematic procedure of developing radionuclide release scenarios was established based on FEP list and Interaction Matrix for near-surface LILW repository. FEPs were screened by experts＇review in terms of domestic situation and combined into scenarios on the basis of Interaction Matrix analysis. Under the assumption of design scenario, The system domain was divided into three sections: Near-field, Far-field and Biosphere. Sub-scenarios for each section were developed, and then scenarios for entire system were built up with sub-scenarios of each section. Finally, sixteen design scenarios for near-surface repository were evaluated A reference scenario and other noteworthy scenarios were selected through experts＇scenario screening.
Shape Optimization of the H-shape Spacer Grid Spring Structure
Yoon, Kyung-Ho ; Kim, Hyung-Kyu ; Kang, Heung-Seok ; Song, Kee-Nam ; Park, Ki-Jong ;
Nuclear Engineering and Technology, volume 33, issue 5, 2001, Pages 547~555
In pressurized light water reactor fuel assembly, spacer grids support nuclear fuel rods both laterally and vertically. The fuel rods are supported by spacer grid springs and grid dimples that are located in the grid cell. The support system allows for some thermal expansion and imbalance of the fuel rods. The imbalance is absorbed by elastic energy to prevent coolant flow- induced vibration damage. Design requirements are defined and a design process is established. The design process includes mathematical optimization as well as practical design method. The shape of the grid spring is designed to maintain its function during the lifetime of the fuel assembly. A structural optimization method is employed for the shape design. Since the optimization is carried out in the linear range of finite element analysis, the optimum solution is verified by nonlinear analysis. A good design is found and the final design is compared with the initial conceptual design. Commercial codes are utilized for structural analysis and optimization.