• Nuclear Engineering and Technology
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• 제46권5호
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• pp.619-632
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• 2014

The Best Estimate Plus Uncertainty (BEPU) method has been widely used to evaluate the uncertainty of a best-estimate thermal hydraulic system code against a figure of merit. This uncertainty is typically evaluated based on the physical model's uncertainties determined by expert judgment. This paper introduces the application of data assimilation methodology to determine the uncertainty bands of the physical models, e.g., the mean value and standard deviation of the parameters, based upon the statistical approach rather than expert judgment. Data assimilation suggests a mathematical methodology for the best estimate bias and the uncertainties of the physical models which optimize the system response following the calibration of model parameters and responses. The mathematical approaches include deterministic and probabilistic methods of data assimilation to solve both linear and nonlinear problems with the a posteriori distribution of parameters derived based on Bayes' theorem. The inverse problem was solved analytically to obtain the mean value and standard deviation of the parameters assuming Gaussian distributions for the parameters and responses, and a sampling method was utilized to illustrate the non-Gaussian a posteriori distributions of parameters. SPACE is used to demonstrate the data assimilation method by determining the bias and the uncertainty bands of the physical models employing Bennett's heated tube test data and Becker's post critical heat flux experimental data. Based on the results of the data assimilation process, the major sources of the modeling uncertainties were identified for further model development.

• Nuclear Engineering and Technology
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• 제48권3호
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• pp.684-701
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• 2016

The Gaussian process model (GPM) is a flexible surrogate model that can be used for nonparametric regression for multivariate problems. A unique feature of the GPM is that a prediction variance is automatically provided with the regression function. In this paper, we estimate the safety margin of a nuclear power plant by performing regression on the output of best-estimate simulations of a large-break loss-of-coolant accident with sampling of safety system configuration, sequence timing, technical specifications, and thermal hydraulic parameter uncertainties. The key aspect of our approach is that the GPM regression is only performed on the dominant input variables, the safety injection flow rate and the delay time for AC powered pumps to start representing sequence timing uncertainty, providing a predictive model for the peak clad temperature during a reflood phase. Other uncertainties are interpreted as contributors to the measurement noise of the code output and are implicitly treated in the GPM in the noise variance term, providing local uncertainty bounds for the peak clad temperature. We discuss the applicability of the foregoing method to reduce the use of conservative assumptions in best estimate plus uncertainty (BEPU) and Level 1 probabilistic safety assessment (PSA) success criteria definitions while dealing with a large number of uncertainties.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 추계학술발표회요약집
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• pp.173.2-173
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• 1999

• 아동학회지
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• 제9권1호
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• pp.81-91
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• 1988

The present research studied the relationship between children's social competence and popularity and examined popularity variables for the prediction of children's social competence. The subjects of this study were 80 children, 40 boys and 40 girls at age 5. Children's social competence was measured by the children's teachers with the use of the Social Competence Scale (Kohn & Rossman, 1972). Children's popularity and unpopularity were obtained from the subjects with the use of Moore's (1973) Sociometric Status Test. Teacher's estimate of the popularity of children was obtained with the use of Connolly & Doyle's (1981) Teacher Rankings of Popularity. The analysis of the data was by Pearson's Correlation Coefficient, and Stepwise Multiple Regression. There were significant relationships between children's social competence and popularity (children's popularity, children's unpopularity, teacher's popularity). Teacher's estimate of child's popularity was the best variable with which to predict children's social competence, the second best variable was children's popularity as measured by Moore's Sociometric Test.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2002년도 학술발표회 발표논문집
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• pp.229-232
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• 2002

This study was conducted to estimate the design flood by the determination of best fitting order of LH-moments of the annual maximum series at six and nine watersheds in Korea and Australia, respectively. Adequacy for flood flow data was confirmed by the tests of independence, homogeneity, and outliers. Gumbel (GUM), Generalized Extreme Value (GEV), Generalized Pareto (GPA), and Generalized Logistic (GLO) distributions were applied to get the best fitting frequency distribution for flood flow data. Theoretical bases of L, L1, L2, L3 and L4-moments were derived to estimate the parameters of 4 distributions. L, L1, L2, L3 and L4-moment ratio diagrams (LH-moments ratio diagram) were developed in this study.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2004년도 춘계학술대회 논문집
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• pp.101-108
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• 2004

KEPRI has developed an Nuclear Steam Supply System(NSSS) thermal-hydraulics simulation program (called ARTS-KORI), based on the best-estimate system code, RETRAN, as a part of the development project for the KORI unit 1 Nuclear Power Plant Simulator. A number of code modifications, such as simplifications and removing of discontinuities of the physical correlations, were made in order to change the RETRAN code as an nuclear Steam Supply System thermal-hydraulics engine in the simulator. Some simplified models and a backup system were also developed. This paper briefly presents the results of non-integrated standalone test of ARTS-KORI.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2004년도 춘계학술대회 논문집
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• pp.94-100
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• 2004

KEPRI has developed an Nuclear Steam Supply System(NSSS) thermal-hydraulic simulation program (called ARTS-KORIl) based on the best-estimate system code, RETRAN, as a part of the development project for the KORI unit 1 nuclear power plant simulator. To develop the RETRAN code as an NSSS T/H engine for the simulator, a number of code modifications, such as simplifications and removing of discontinuities of the physical correlations, were made to satisfy the simulator requirements of robustness and real time calculation capability Some simplified models and a backup system were also developed to simulate some transients that cannot be efficiently calculated by the RETRAN part of ARTS-KORIl.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.417-422
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• 1996

The KNGR has an advanced ECCS design feature which employs four mechanically-separated SI trains where each train consisting of one HPSI pump and one SIT injects ECC water directly into the reactor vessel downcomer annulus. To demonstrate that the KNGR ECCS design features meet the EPRI ALWR requirements of no core uncovery for a break of up to 6 inch diameter, small break LOCA cases with various break sizes were analyzed using a best-estimate analytical procedure. Two kinds of break locations are considered: cold leg and DVI line breaks. It was observed that the KNGR ECC design can tolerate a cold leg break of up to 10 inches with no core uncovery. However. since DVI line break with 6 inch diameter undergoes slight core uncovery. further investigation is required for KNGR SIS optimization.

• 한국군사과학기술학회지
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• 제9권1호
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• pp.99-108
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• 2006

In this paper, we analyzed the characteristics of emitter geolocation coverage area within which the emitter lies with a specified probability based on the LOBs(Line of Bearing) of sensors. Stansfield and MSD algorithms were applied to calculate BPE(Best Point Estimate), EEP(Elliptical Error Probable) and CEP(Circular Error Probable), They used the weighting factors composed of ${\sigma}_{Phi}$ (bearing error), QF(quality factor), $P_{e}$ (probability being inside) to optimize the performance. The characteristics of EEP was investigated in the change of them and those of CEP was analyzed based on the deployment of sensors.

• 생약학회지
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• 제23권3호
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• pp.153-157
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• 1992

The deodorizing responses of the steam distillate from some medicinal plants(G-3) on three representative malodors were evaluated by estimating the best estimate threshold(BET) of odor responses. With a single spray of G-3, the BETs of malodors such as ammonia, acetic acid, and ethyl acetate were found to increase 4.11, 32.6 and 13.1 fold, respectively, which indicated G-3 possessed a potent deodorizing activity. The deodorizing potency of G-3 was also demonstrated to be as high as and even higher than those of the commercial deodorizing agents.