• Nuclear Engineering and Technology
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• 제51권1호
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• pp.198-206
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• 2019

A new methodology to analyze the nuclear material accountability for pyroprocessing system is developed. The $Pu-to-^{244}Cm$ ratio quantification is one of the methods for Pu accountancy in pyroprocessing. However, an uncertainty in the $Pu-to-^{244}Cm$ ratio due to the non-uniform composition in used fuel assemblies can affect the accountancy of Pu. A random variable, LOPu, is developed to analyze the probability of detection for Pu diversion of hypothetical scenarios at a pyroprocessing facility considering the uncertainty in $Pu-to-^{244}Cm$ ratio estimation. The analysis is carried out by the hypothesis testing and the event tree method. The probability of detection for diversion of 8 kg Pu is found to be less than 95% if a large size granule consisting of small size particles gets sampled for measurements. To increase the probability of detection more than 95%, first, a new Material Balance Area (MBA) structure consisting of more number of Key Measurement Points (KMPs) is designed. This multiple KMP-measurement for the MBA shows the probability of detection for 8 kg Pu diversion is greater than 96%. Increasing the granule sample number from one to ten also shows the probability of detection is greater than 95% in the most ranges for granule and powder sizes.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.617-626
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• 2022

To effectively monitor the variety of distributions of neutron flux, fuel power or temperatures in the reactor core, usually the ex-core and in-core neutron detectors are employed. The thermocouples for temperature measurement are installed in the coolant inlet or outlet of the respective fuel assemblies. It is necessary to reconstruct the measurement information of the whole reactor position. However, the reading of different types of detector in the core reflects different aspects of the 3D power distribution. The feasibility of reconstruction the core three-dimension power distribution by using different combinations of in-core, ex-core and thermocouples detectors is analyzed in this paper to synthesize the useful information of various detectors. A comparison of multilayer perceptron (MLP) network and radial basis function (RBF) network is performed. RBF results are more extreme precision but also more sensitivity to detector failure and uncertainty, compare to MLP networks. This is because that localized neural network could offer conservative regression in RBF. Adding random disturbance in training dataset is helpful to reduce the influence of detector failure and uncertainty. Some convolution neural networks seem to be helpful to get more accurate results by use more spatial layout information, though relative researches are still under way.

• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2698-2703
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• 2024

A bilateral comparison was conducted between the International Atomic Energy Agency (IAEA) and the Korea Research Institute of Standards and Science (KRISS) to measure the absorbed dose to water in accelerator photon beams. KRISS served as a linking laboratory to compare the IAEA standard with the key comparison reference value (KCRV) of the BIPM.RI(I)-K6 program, in which KRISS participated in 2017. Two ionization chambers from the IAEA were used as transfer instruments for the comparison. Both laboratories measured the calibration coefficients of these instruments and calculated the ratios. The ratio of the KRISS standard to the KCRV was applied to obtain the degree of equivalence of the IAEA, along with its uncertainty. The largest deviation of the IAEA measurement from the KCRV was 3.4 mGy/Gy, significantly smaller than the expanded uncertainty of 10.7 mGy/Gy (k = 2, 95% level of confidence). This study demonstrates the equivalence of IAEA's measurement standard for accelerator photon beams to other primary standard dosimetry laboratories. It provides evidence for the satisfactory operation of IAEA's quality management system and enhances the international credibility of the IAEA SSDL network, particularly in high-energy accelerator photon beams from linear accelerators.

• 한국농림기상학회지
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• 제21권4호
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• pp.307-316
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• 2019

농업 분야 온실가스 발생은 토양환경, 기상환경, 작물 생장 등 모든 생태계 변화와 인위적인 영농활동의 상호작용에 따라 변화하여 배출량 변동성의 크기가 매우 크므로 배출량 자료에 대한 신뢰구간 확보가 필요하다. 이에 온실가스 배출량 및 흡수량에 대한 신뢰구간을 정의하는 불확도 평가가 필요하지만 불확도 평가 방법에 대한 연구는 부족한 실정이다. 따라서 본 연구에서는 밭토양에서 발생하는 N₂O 배출량 저감 효과의 유의성을 불확도 추정기법을 통하여 판정하고자 하였다. 질소 비료 시비효과 증진 및 N₂O 배출량 감소를 위한 요소분해효소 억제제 NBPT 함유 원예용 비료, 표준시비, 무시비 등 5처리 집단들의 신뢰구간에 차이가 있는지를 불확도 평가를 통해 확인하였으며, N₂O 배출량 개별 자료들의 변동성을 모두 고려한 신뢰구간을 찾아내어 분석한 결과로 신뢰성 있는 저감 효과(처리간 차이)의 유무를 판정할 수 있었다. 또한 고추와 배추 재배지에서 요소분해효소 억제제 NBPT 함유 원예용 비료를 시용하면 표준시비와 같은 생육상황에서 온실가스 저감효과를 볼 수 있는 것으로 확인되었다.

• 한국안전학회지
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• 제27권1호
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• pp.76-85
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• 2012

This paper proposes a robust damper design technique for adjacent structures against model uncertainty. This approach introduces multi-objective optimization based system identification using measurement information which enables reasonable selection of the perturbation range in the robust design. Moreover, in order to improve the numerical efficiency in sampling the structural models required for the robust design of large structures, we define new objective functions which enable us to minimize the number of candidate models suitable to the purpose of the robust design. In addition, the performance index is newly employed to evaluate the robust performance of the sampled structural models, and the robust design has been performed according to the performance index. As a numerical example to demonstrate the efficiency of the proposed method, 5-story and 10-story two adjacent buildings are taken into account, and the existing and newly proposed robust design approaches are compared with each other. The results demonstrate that the proposed approach can guarantee more robust damper system only using small number of samples of the structural models because of using the measurement information which leads to improvement in the numerical efficiency, compared with the existing robust design methods.

• 한국항공우주학회지
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• 제30권5호
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• pp.118-126
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• 2002

한국항공우주연구원은 추력 3,000 lbf급 고공환경 시험설비인 Altitude Engine Test Facility(AETF)를 갖추고 소형 가스터빈엔진의 고공환경 성능시험에 활용하고 있다. AETF를 국제수준으로 발진시키기 위하여 측정정화도 및 신뢰도 향상을 위한 일련의 연구를 진행하고 있으며 측정불확도 개선을 위한 설비 개선이 일부 진행된 상태이다. 본 연구에서는 해면고도(sea level), 마하수(Mn) 0.3, 0.5, 0.7, 0.9일 때 단축(single spool) 터보제트 엔진에 대한 정상상태 성능시험을 수행하였고, 이를 성능 예측 프로그램(DECK)과 비교분석하였다. 가스터빈엔진의 주요 성능변수인 공기유량, 추력, 비연료소모율에 대하여 측정불확도를 분석하여 총기유랑은 0.791~0.914%, 순추력은 0.851~1.706%의 불확도를 나타내었고 연료 유량의 측정불확도는 1.372~7.348%, 비연료소모율의 측정불확도는 1.642~5.205%로 산정되었다. 또한 본 연구를 통하여 측정불확도 개선 방안이 확인되었다.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2003년도 가을 학술논문집
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• pp.562-571
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• 2003

발전용원자로에서 뱃치방식으로 환경으로 배출된 액체유출물 내에 함유된 방사능 평가 결과에 오차를 유발하는 시료채취, 제조, 방사능 계측, 유출물 배출체적 측정 등 다양한 인자를 분석하였다. 환경배출 방사능 평가에 포함된 많은 인자들은 단일 측정에 의해 얻어지고 환경배출 방사능의 참값을 알 수 없음에 따라, 평가결과의 오차를 예측하는 것은 원칙적으로 불가능하다. 이에 따라 1993년 ISO가 권고한 측정의 불확도 표현지침에 근거하여 액체폐기물 배출방사능에 대한 불확도 평가모델을 수립하고 가상적인 조건에 대한 액체유출물 환경배출 방사능 평가결과의 불확도를 평가하였다. 그 결과, 액체유출물을 통한 환경배출 방사능 평가결과에 불확도를 유발하는 인자의 상대적인 기여도는 배출폐액의 체적, 시료의 체적, 총방사능 계측값의 순서를 갖는 것으로 나타났다. 또한 개별 변수의 확률분포와 특성값을 토대로 몬테칼로 모사법을 적용하여 최종 환경배출 방사능 평가결과의 확률분포를 해석함으로써, 지금까지 단일 값을 평가 및 보고되었던 발전용 원자로의 액체상 방사성물질 환경배출량이 실제로는 일정한 확률분포를 갖고 있음을 확인하였다.

• 한국전자통신학회논문지
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• 제13권1호
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• pp.77-84
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• 2018

터빈유량계(Turbine flowmeter)는 유량 측정시 높은 정확도와 반복성을 위해 선택되지만 교정시의 표준 환경 조건과 현장에서의 환경 조건 차이로 다양한 측정 불확도 요인을 발생시킨다. 또한 교정된 측정값 외의 구간에서의 사용을 위해 신뢰성 높은 보간 기법(Interpolation method)이 필요하다. 따라서 본 논문에서는 유량 측정(Flow measurement) 신뢰성 향상을 위해 터빈유량계의 출력 신호의 정확한 측정과 교정된 결과값의 보간, 온도변화를 실시간 보정(correction)하는 장비를 설계 및 제작하고 성능 검증을 수행함으로 현장에서의 측정 신뢰도를 확보하였다.

• 대한조선학회논문집
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• 제51권4호
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• pp.311-320
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• 2014

Test uncertainty of a towed underwater Stereoscopic Particle Image Velocimetry (SPIV) system was assessed in a towing tank. To estimate the systematic error and random error of mean velocity and turbulence properties measurement, velocity field of uniform flow was measured. Total uncertainty of the axial component of mean velocity was 1.45% of the uniform flow speed and total uncertainty of turbulence properties was 3.03%. Besides, variation of particle displacement was applied to identify the change of error distribution. In results for variation of particle displacement, the error rapidly increases with particle movement under one pixel. In addition, a nominal wake of a model ship was measured and compared with existing experimental data by five-hole Pitot tubes, Pitot-static tube, and hot wire anemometer. For mean velocity, small local vortex was identified with high spatial resolution of SPIV, but has serious disagreement in local maxima of turbulence properties due to limited sampling rate.

• 센서학회지
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• 제13권6호
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• pp.411-416
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• 2004

In the international temperature scale of 1990 (ITS-90), standard platinum resistance thermometer (SPRT) is a defining standard thermometer used in the temperature range from 13.8033 K to $961^{\circ}C$. Uncertainty of SPRT is about several mK and uncertainty of defining fixed points of the ITS-90 which is used for calibrating SPRT is about several tenth of mK. Above $0^{\circ}C$. the defining fixed points are gallium melting point and indium, tin, zinc, aluminium and silver freezing points which are all realized using an electric furnace or a liquid bath. To realize freezing point of tin ($231.928^{\circ}C$) and zinc ($419.527^{\cir}C$), two 3-zone furnaces which have 3 electric heaters were manufactured. Temperature gradient of the constructed furnaces were tested. Uncertainty caused by temperature gradient of furnace and immersion effect of SPRT in the sealed-type freezing point cells were evaluated 0.038 mK for tin freezing point and 0.036 mK for zinc freezing point.