Maintaining fuel sheath integrity during dry storage is important. Intact sheath acts as the primary containment barrier for both fuel pellets and fission products over the dry storage periods and during subsequent fuel handling operations. In KNF, in-house fuel performance code was developed to predict the overall behavior of a fuel rod under normal operating conditions. It includes the analysis modules to predict temperature, pellet cracking and deformation, sheath stress and strain at the mid-plane of the pellet and pellet-pellet interfaces, fission gas release and internal gas pressure. The main focus of the code is to provide information on initial conditions prior to dry storage, such as fission gas inventory and its distribution within the fuel pellet, initial volumes of storage spaces and their locations, radial profile of heat generation within the pellet, etc. To upgrade the developed code that address all the damage mechanisms, the first step was a review of the available technical information on phenomena relevant to fuel integrity. Potential degradation mechanisms that may affect sheath integrity of CANDU spent fuel during dry storage are: creep rupture under internal gas pressure, sheath oxidation in air environment, stress corrosion cracking (SCC), delayed hydride cracking (DHC), and sheath splitting due to UO2 oxidation for a defective fuel. The failure by creep rupture, SCC or DHC is in the form of small cracks or punctures. The failure by sheath oxidation or sheath splitting due to UO2 oxidation results in a gross sheath rupture. The second step was to examine the technical bases of all modules of the in-house code, identify and extend the ranges of all modules to required operating ranges. This step assessed the degradation mechanisms for the fuel integrity. The objective of this assessment is to predict the probability of sheath through-wall failure by a degradation mechanisms as a function of the sheath temperature during dry storage. Further improvements being considered include upgrades of the analysis module to achieve sufficient accuracy in key output parameters. The emphasis in the near future will be on validation of the inhouse code according to a rigorous and formal methodology. The developed models provide a platform for research and industrial applications, including the design of fuel behavior experiments and prediction of safe operating margins for CANDU spent fuel.

수생태계 생물학적 온전성을 평가하기 위하여 국내 하천 및 하구 923개 지점의 자료를 근거로 한국형 다중형 돌말지수 (KMDI)를 개발하고, 이를 금강수계 233개 지점을 대상으로 온전성평가를 실시하여 단일형 돌말지수들과 비교 검토하였다. KMDI의 개발은 1) 먼저 선행문헌들을 참고로 300개 이상의 메트릭을 추출하고, 2) 이 중 설명력이 높은 46개 후보 메트릭을 선택하며, 3) 각 메트릭 값들의 변이성, 중복성, 변별력, 환경에 대한 민감성 등을 검증하고, 최종적으로 5가지의 메트릭을 선정하였다. KMDI는 매트릭의 단순합으로 표현하고, 환경요인들에 대한 신뢰성 검토 결과, 토지이용, BOD, TN, 전기전도도 등에 대해 높은 민감성 및 설명력을 보였으나 단일형 돌말지수들 보다는 동일 지점의 생물학적 온전성은 다소 높게 평가되는 특성을 보였다. 추후 국내는 물론 지역에 상관없이 적용가능한 설명력 높은 매트릭의 발굴 및 정확한 돌말류 분석 연구가 뒷따라야 될 것으로 판단되었다.

철근콘크리트 구조물의 보수ㆍ보강 등의 유지관리를 위해서는 내구성과 내하성을 동시에 고려한 건전성평가의 의사결정기준이 절실히 요구된다. 본 논문은 CART-ANFIS을 사용하는 철근콘크리트 구조물에 대하여 효율적인 모델을 나타내었다. 철근콘크리트 구조물의 손상과 진단 등에 활용되어온 분류형 전문가시스템의 일종인 퍼지이론을 이용한 결정목 구조와 기존의 인공신경망을 이용한 결정목 구조의 건전성평가를 비교 분석한다. 손상된 철근콘크리트의 내구성 회복을 위한 보강설계 이론과 내하력 증가를 위한 보장설계 이론을 정립시켜 손상검출의 산정식을 유도하였다. 본 연구의 건전성 평가시스템 모델을 이용함으로서 보다 효율적인 철근콘크리트 유지관리 뿐만 아니라 생애주기비용 예측을 수행 할 수 있다.

어류군집을 이용한 생물보전지수(Index of Biological Integrity, IBI)와 서식지 평가지수 (qoalitativeHabitatEvaluationlndex, QHEI)를 적용하여 금호강의 수서 생태계를 평가하였다. 총체적으로 금호강의 IBI값은 13-37 범위에 있었으며, 연 평균값은 23(n=25, Std. error=1.16)으로서 Karr(1981) 와 U.S. EPA (1993) 기준에 따르면 "Poor" 또는 "Very Po

This study presents meteorological data integrity to improve environmental quality assessment in Yongdam catchment. The study examines both extreme ranges of meteorological data measurements and data reliability which include maximum and minimum temperature, relative humidity, dew point temperature, radiation, heat flux. There were some outliers and missing data from the measurements. In addition, the latent heat flux and sensible heat flux data were not reasonable and evapotranspiration data did not match at some points. The accuracy and consistency of data stored in a database for the study were secured from the data integrity. Users need to take caution when using meteorological data from the Yongdam catchment in the preparation of water resources planning, environmental impact assessment, and natural hazards analysis.

본 연구는 현재 상태에서 콘크리트 내부의 균열, 공극, 결함 등을 식별 및 판단하고 일반적인 초음파법 및 반발경도법 외에 S-wave 및 R-wave를 사용하여 미래의 머신러닝 기법의 적용 가능성을 설명합니다. 또한, 다양한 머신러닝 기법 중에서 서포트벡터머신(SVM) 및 인공신경망(ANN)을 사용하여 콘크리트 건전성 평가에 대한 모델 개발을 통해 실험데이터의 예측 결과에 대한 비교분석을 진행하였고 최종적으로 SVM 모델을 제시하였다.

The Optical Wide-field patroL-Network (OWL-Net) is a global optical network for Space Situational Awareness in Korea. The primary operational goal of the OWL-Net is to track Low Earth Orbit (LEO) satellites operated by Korea and to monitor the Geostationary Earth Orbit (GEO) region near the Korean peninsula. To obtain dense measurements on LEO tracking, the chopper system was adopted in the OWL-Net’s back-end system. Dozens of angle-only measurements can be obtained for a single shot with the observation mode for LEO tracking. In previous work, the reduction process of the LEO tracking data was presented, along with the mechanical specification of the back-end system of the OWL-Net. In this research, we describe an integrity assessment method of time-position matching and verification of results from real observations of LEO satellites. The change rate of the angle of each streak in the shot was checked to assess the results of the matching process. The time error due to the chopper rotation motion was corrected after re-matching of time and position. The corrected measurements were compared with the simulated observation data, which were taken from the Consolidated Prediction File from the International Laser Ranging Service. The comparison results are presented in the In-track and Cross-track frame.

The signal characteristic of radar wave on concrete decks is determined by the attenuation of the radar due to the conversion of EM(Electromagnetic) energy to thermal energy through electrical conduction, dielectric relaxation, scattering, and geometric spreading. In this study, it is found that the attenuation of radar signal received on top rebars in bare deck concrete with 2 way travel time shows a general decreasing linear trend because of its same relative permittivity and conductivity. The radar signal after depth-normalization, can then be interpreted as being principally influenced by the content of chlorides penetrating cover concrete, which caused corrosion of rebars in bridge decks.

The ex-vessel steam explosion may occur when, during a severe reactor accident, the molten core pours into the water in the reactor cavity. These dynamic loads on the cavity wall could potentially lead to the significant failure of the cavity wall. But the phenomenon like this steam explosion includes big uncertainty in estimating the impulsive pressure loading of RCB. In this study, risk based integrity assessment method of the NPP structure subjected to steam explosion load was suggested to capture these uncertainties involved during the structural integrity assessment of the Nuclear power plant.