• Nuclear Engineering and Technology
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• 제52권1호
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• pp.135-147
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• 2020

A methodology for evaluation of mechanical and thermal effects of localized non-axisymmetric oxidation in zircaloy claddings on LWR fuel reliability is proposed. To this end, the basic capabilities of the FALCON fuel behaviour code are used. Examples of methodology application to adjustment of selected operational limits for modern BWR fuel rods, to capture effects of the excess local oxidation, are presented. Specifically, the limiting rod internal pressure for the onset of cladding lift-off is reduced, depending on initial excess oxidation spot sizes. Also, the power limits for Anticipated Operational Occurrences are adjusted, to preclude fuel melting and cladding failure due to PCMI and PCI-SCC in the affected fuel rods.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2002년도 춘계공동학술발표회요약집
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• pp.41.1-41
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• 2002

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제16권3호
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• pp.163-172
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• 2016

Electric load forecasting is essential for effective power system planning and operation. Complex and nonlinear relationships exist between the electric loads and their exogenous factors. In addition, time-series load data has non-stationary characteristics, such as trend, seasonality and anomalous day effects, making it difficult to predict the future loads. This paper proposes a locally-weighted polynomial neural network (LWPNN), which is a combination of a polynomial neural network (PNN) and locally-weighted regression (LWR) for daily shortterm peak load forecasting. Model over-fitting problems can be prevented effectively because PNN has an automatic structure identification mechanism for nonlinear system modeling. LWR applied to optimize the regression coefficients of LWPNN only uses the locally-weighted learning data points located in the neighborhood of the current query point instead of using all data points. LWPNN is very effective and suitable for predicting an electric load series with nonlinear and non-stationary characteristics. To confirm the effectiveness, the proposed LWPNN, standard PNN, support vector regression and artificial neural network are applied to a real world daily peak load dataset in Korea. The proposed LWPNN shows significantly good prediction accuracy compared to the other methods.

• Nuclear Engineering and Technology
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• 제41권6호
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• pp.753-764
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• 2009

JAEA started the LSTF experiments in 1985 for the fourth stage of the ROSA Program (ROSA-IV) for the LWR thermal-hydraulic safety research to identify and investigate the thermal-hydraulic phenomena and to confirm the effectiveness of ECCS during small-break LOCAs and operational transients. The LSTF experiments are underway for the ROSA-V Program and the OECD/NEA ROSA Project that intends to resolve issues in thermal-hydraulic analyses relevant to LWR safety. Six types of the LSTF experiments have been done for both the system integral and separate-effect experiments among international members from 14 countries. Results of four experiments for the ROSA Project are briefly presented with analysis by a best-estimate (BE) code and a computational fluid dynamics (CFD) code to illustrate the capability of the LSTF and codes to simulate the thermal-hydraulic phenomena that may appear during SBLOCAs and transients. The thermal-hydraulic phenomena dealt with are coolant mixing and temperature stratification, water hammer up to high system pressure, natural circulation under high core power condition, and non-condensable gas effect during asymmetric SG depressurization as an AM action.

• 제어로봇시스템학회논문지
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• 제22권5호
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• pp.367-373
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• 2016

In this paper, range measurement performance of LRF (Laser Range Finder) module and image contrast of color CCD camera are evaluated under the aerosol (high temperature steam) environments, which are simulated severe accident conditions of the LWR (Light-Water-Reactor) nuclear power plant. Data of LRF and color CCD camera are key informations, which are needed in the implementation of SLAM (Simultaneous Localization and Mapping) function for emergency response robot system to cope with urgently accidents of the nuclear power plant.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.819-823
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• 2024

The main criteria used in NEI 18-04 to define SSCs as risk-significant include (1) the SSC is required to keep all LBEs within the F-C target, and (2) the total frequency with the SSC failed exceeds 1% of the limit for at least one of the three cumulative risk metrics used for evaluating the integrated plant risk. The first one is a reasonable criterion in determining the risk significant SSCs. However, the second criterion may not be adequate to serve the purpose of determining the risk significance of SSCs. In the second criterion, the cumulative risk metric values representing the integrated plant risk (less the preventive and mitigative effects of the SSC being evaluated) are compared to a risk limit that represents a very small contribution to the overall integrated plant risk, which corresponds appropriately to the contributions from individual SSCs. The easiest approach to redefine the NEI 18-04 definition of risk-significant SSCs in relation to the integrated plant risk metrics is to compare the difference, between the risk metric value calculated with the SSC failed and the risk metric value calculated with the SSC credited, with 1% of the risk limit established for the integrated plant risk metrics.

• 한국농림기상학회지
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• 제14권2호
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• pp.79-89
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• 2012

본 연구는 광환경 변화에 따른 병풍쌈의 엽록소 함량, 광합성 특성, 엽록소형광반응 그리고 생장 특성을 조사하기 위해 실시하였으며, 실험을 위해 병풍쌈을 무처리구(full sunlight)와 3개의 서로 다른 피음조건(88~93%, 65~75% and 45%~55% of full sunlight)에서 생육시켰다. 병풍쌈은 피음수준이 증가할수록 총 엽록소 함량, 광화학반응효율, T/R율, SLA, LAR, LWR은 증가하고 암호흡은 감소하여, 낮은 광조건에서 빛의 흡수량과 광합성에 대한 이용효율을 높이는 반응을 나타냈다. 5월의 중피음처리구에서 가장 높은 최대광합성속도와 순양자수율을 나타냈으며, 피음처리구보다 전광처리구에서 가장 낮은 최대광합성속도, 광화학반응효율, 엽록소 함량을 나타냈다. 위의 결과에 따라 병풍쌈은 음지식물로 강한 광에 대한 민감성이 매우 높고, 광을 제한하여도 강피음 상태를 지속하게 되면 광합성 능력이 크게 감소될 수 있으며, 건전한 생육을 위해서는 노천광의 65~75%를 차단시킨 광환경 조건이 적합하다고 생각된다.

• 한국산림과학회지
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• 제100권4호
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• pp.598-608
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• 2011

본 연구는 우리나라 난대수종 중의 하나인 가시나무를 1년생 용기묘로 생산하고자 할 때 피음 및 시비처리가 용기묘의 생장과 품질에 미치는 영향을 구명하고자 실시되었다. 피음은 전광 및 전광의 35%, 55%, 75%의 수준으로 조절하였으며, 시비수준은 무시비구와 함께 수용성 복합비료(N:P:K=19:19:19, v/v)를 1000, 2000, 3000 ppm으로 조절하여 실시하였다. 본 실험을 통하여 가장 높은 간장생장은 21.1 cm를 보인 55% 피음의 2000 ppm 시비구로 조사되었으며, 근원경생장에 있어서는 35% 피음의 2000 ppm 시비구에서 3.96 mm로 가장 좋았다. 우수한 간장과 근원경생장을 보인 35%와 55% 피음에서 시비농도와 관계없이 시비구 전체 묘목의 H/D율을 보면 4.27~5.26의 범위를 보였다. 잎의 건물생산량이 가장 높은 처리구는 1.292 g을 기록한 55% 피음의 2000 ppm 시비구이었으며, 줄기와 뿌리는 각각 0.592 g과 0.998 g으로 조사된 35% 피음의 2000 ppm 시비구이었다. 묘목 전체 건물생산량은 35% 피음의 2000 ppm 시비구에서 가장 높은 생산량을 보였으며, 55% 피음의 2000 ppm, 35% 피음의 3000 ppm 시비구 순으로 높게 나타났다. 피음 및 시비처리에 따른 가시나무 LWR의 가장 높은 값은 75% 피음의 3000 ppm 시비구로 조사되었으며, RWR은 피음처리 수준에 관계없이 시비처리한 묘목이 무시비처리 묘목보다 낮았다. 전반적으로 높은 QI는 55%피음의 시비처리구들이었으며, 가장 높은 QI는 35% 피음의 2000 ppm 시비구로 조사되었다. 본 실험의 결과로 볼 때 생장이 뛰어나며 품질지수가 높은 가시나무 1년생 용기묘 생산에 적합한 피음수준은 35~55% 정도로, 시비수준은 2000 ppm이 적합한 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제41권7호
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• pp.929-944
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• 2009

The present study is concerned with the extension of the Effective Convectivity Model (ECM) to the phase-change problem to simulate the dynamics of the melt pool formation in a Light Water Reactor (LWR) lower plenum during hypothetical severe accident progression. The ECM uses heat transfer characteristic velocities to describe turbulent natural convection of a melt pool. The simple approach of the ECM method allows implementing different models of the characteristic velocity in a mushy zone for non-eutectic mixtures. The Phase-change ECM (PECM) was examined using three models of the characteristic velocities in a mushy zone and its performance was compared. The PECM was validated using a dual-tier approach, namely validations against existing experimental data (the SIMECO experiment) and validations against results obtained from Computational Fluid Dynamics (CFD) simulations. The results predicted by the PECM implementing the linear dependency of mushy-zone characteristic velocity on fluid fraction are well agreed with the experimental correlation and CFD simulation results. The PECM was applied to simulation of melt pool formation heat transfer in a Pressurized Water Reactor (PWR) and Boiling Water Reactor (BWR) lower plenum. The study suggests that the PECM is an adequate and effective tool to compute the dynamics of core melt pool formation.

• Nuclear Engineering and Technology
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• 제41권5호
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• pp.575-602
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• 2009

In the wake of the Three Mile Island accident, vigorous research efforts were initiated to acquire a basic knowledge of the progression and consequences of accidents that involve a substantial degree of core degradation and melting. The primary emphasis of this research was placed on containment integrity, with: i) hydrogen combustion-detonation, ii) steam explosion, iii) direct containment heating (DCH), and iv) melt attack on the BWR Mark-I containment shell identified as energetic processes that could lead to early containment failure (i.e., within the first 24 hours of the accident). Should the core melt fail the reactor vessel, then non-condensable gas production from Molten Core-Concrete Interaction (MCCI) was identified as a mechanism that could fail the containment by pressurization over the long term. One signification question that arose as part of this investigation was the effectiveness of water in terminating an MCCI by flooding the interacting masses from above, thereby quenching the molten core debris and rendering it permanently coolable. Successful quenching of the core melt would prevent basemat melt through, as well as continued containment pressurization by non-condensable gas production, and so the accident progression would be successfully terminated without release of radioactivity to the environment. Based on these potential merits, ex-vessel corium coolability has been the focus of extensive research over the last 20 years as a potential accident management strategy for current plants. In addition, outcomes from this research have impacted the accident management strategies for the Gen III+LWR plant designs that are currently being deployed around the world. This paper provides: i) an historical overview of corium coolability research, ii) summarizes the current status of research in this area, and iii) highlights trends in severe accident management strategies that have evolved based on the findings from this work.