• Nuclear Engineering and Technology
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• 제56권4호
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• pp.1165-1203
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• 2024

In the paper we validate theoretical models of the pulse against experimental data from the Jozef Stefan Institute TRIGA Mark II research reactor. Data from all pulse experiments since 1991 have been collected, analysed and are publicly available. This paper summarizes the validation study, which is focused on the comparison between experimental values, theoretical predictions (Fuchs-Hansen and Nordheim-Fuchs models) and calculation using computational program Improved Pulse Model. The results show that the theoretical models predicts higher maximum power but lower total released energy, full width at half maximum and the time when the maximum power is reached is shorter, compared to Improved Pulse Model. We evaluate the uncertainties in pulse physical parameters (maximum power, total released energy and full width at half maximum) due to uncertainties in reactor physical parameters (inserted reactivity, delayed neutron fraction, prompt neutron lifetime and effective temperature reactivity coefficient of fuel). It is found that taking into account overestimated correlation of reactor physical parameters does not significantly affect the estimated uncertainties of pulse physical parameters. The relative uncertainties of pulse physical parameters decrease with increasing inserted reactivity. If all reactor physical parameters feature an uncorrelated uncertainty of 10 % the estimated total uncertainty in peak pulse power at 3 $ inserted reactivity is 59 %, where significant contributions come from uncertainties in prompt neutron lifetime and effective temperature reactivity coefficient of fuel. In addition we analyse contribution of two physical mechanisms (Doppler broadening of resonances and neutron spectrum shift) that contribute to the temperature reactivity coefficient of fuel. The Doppler effect contributes around 30 %-15 % while the rest is due to the thermal spectrum hardening for a temperature range between 300 K and 800 K.

• 제어로봇시스템학회논문지
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• 제18권4호
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• pp.295-301
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• 2012

This paper deals with the design of robust DSMC (Discrete-Time Sliding Mode Control) scheme in order to overcome system uncertainty in steering system with mechanically joined structure. The proposed control scheme is one of robust control schemes based on system dynamics. Therefore, system dynamics required is not obtained from physical law but SCM (Signal Compression Method) through experiment in order to avoid complicate mathematical development and save time. However, SCM has a shortcoming that is the limitation of with $2^{nd}$ order linear model which does not include the dynamic of high-frequency band. Thus, considering system uncertainty, DSMC is designed. In addition, to reduce the chattering problem of DSMC, DSMC is derived from the reaching law and the Lyapunov stability condition. It is found that the proposed control scheme has robustness in spite of the perturbation of system uncertainty through computer simulation.

• Nuclear Engineering and Technology
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• 제37권2호
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• pp.139-150
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• 2005

A robust control design procedure for a nuclear reactor has been developed and experimentally validated on the Penn State TRIGA research reactor. The utilization of the robust controller as a component of an autonomous control system is also demonstrated. Two methods of specifying a low order (fourth-order) nominal-plant model for a robust control design were evaluated: 1) by approximation based on the 'physics' of the process and 2) by an optimal Hankel approximation of a higher order plant model. The uncertainty between the nominal plant models and the higher order plant model is supplied as a specification to the ,u-synthesis robust control design procedure. Two methods of quantifying uncertainty were evaluated: 1) a combination of additive and multiplicative uncertainty and 2) multiplicative uncertainty alone. The conclusions are that the optimal Hankel approximation and a combination of additive and multiplicative uncertainty are the best approach to design robust control for this application. The results from nonlinear simulation testing and the physical experiments are consistent and thus help to confirm the correctness of the robust control design procedures and conclusions.

• 시스템엔지니어링학술지
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• 제15권1호
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• pp.51-59
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• 2019

After Fukushima Dai-ichi NPP accident, the need for implementation of diverse and flexible coping strategies (FLEX) became evident. However, to ensure the effectiveness of the safety strategy, it is essential to quantify the uncertainties associated with the station blackout (SBO) scenario as well as the operator actions. In this paper, a systems engineering approach for uncertainty analysis (UA) of a SBO scenario in advanced pressurized water reactor is performed. MARS-KS is used as a best estimate thermal-hydraulic code and is loosely-coupled with Dakota software which is employed to develop the uncertainty quantification framework. Furthermore, the systems engineering approach is adopted to identify the requirements, functions and physical architecture, and to develop the verification and validation plan. For the preliminary analysis, 13 uncertainty parameters are propagated through the model to evaluate the stability and convergence of the framework. The developed framework will ultimately be used to quantify the aleatory and epistemic uncertainties associated with an extended SBO accident scenario and assess the coping capability of APR1400 and the effectiveness of the implemented FLEX strategies.

• 대한통합의학회지
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• 제10권4호
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• pp.153-163
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• 2022

Purpose : The purpose of this study was to investigate the differences between uncertainty of chronic diseases and quality of life with regard to elderly people. Methods : The participants of this study were 350 elderly people, aged over 65 years. The collected data were analyzed using the SPSS Window program and the general characteristics of the participants and sub-domains of quality of life were analyzed by several frequency analyses and descriptive statistics such as mean, standard deviation, skewness, and kurtosis. Further, the differences between the sub-domains of uncertainty and sub-domains of quality of life were analyzed through independent t-test and one-way ANOVA. In order to reach conclusive results, post-test was analyzed by the Scheffe test. In addition, Pearson's correlation analysis was performed to determine the correlation between the target categories. A significance level of 𝛼=.05 was used to verify statistical significance. Results : As a result of examining "uncertainty" with respect to general characteristics, such as older age, low educational background, and chronic diseases, it was observed that the more intense these factors became, the more the level of uncertainty increased. In addition, it was also noted that except "accompanying diseases" in social domain, the participants enjoyed a high level of quality of life. The correlation was noted between domains of complexity and sociality (p<.01), domains of inconsistency and sociality (p<.01), domains of complexity and living environment (p<.01), domains of inconsistency and living environment (p<.01), and total score of uncertainty and total quality of life (p<.01). Conclusion : In this study, differences were found between "uncertainty" and "quality of life" of elderly people; the correlation between the sub-domains based on general traits was found to be negative (-). This suggests that objective evidence can be presented for the prevention of diseases by using mental health programs for the elderly in future.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 1987년도 제29회 수공학연구발표회논문초록집
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• pp.123-137
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• 1987

The groundwater hydrographs due to the recharge of water table aquifer resulting from rainfall are simulated by relating the existing linearized method, which is originally the non-linear equation suggested by Boussinesq, to the basin charcteristics. To thes end, the recharge curve is assumed as the skewed distribution of sine curve, and the parameters contained in the equation are determined from the geomorphologic and soil maps. The whole drainage area is divied in order to consider the spatial variation of parameters. The obtained parameters are tried for several cases with different values given arbitrarily to study the aspects of hydrographs according to their variation. This procedures are applied to the natural basin of Bocheong watershed(area:475.5$\textrm{km}^2$) in Korea. As a result, it is shown that considerable uncertainty is expressed for the results obtained with the given values of parameters. Thus, such uncertainty should be precluded to a certain extent by examining and observing the physical characteristics as much as possible for the determination of groundwater flows.

• Nuclear Engineering and Technology
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• 제54권2호
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• pp.479-485
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• 2022

At the Korea Institute of Radiological and Medical Sciences, physical human phantoms were developed to evaluate various radiation protection quantities, based on the mesh-type reference computational phantoms of the International Commission on Radiological Protection. The physical human phantoms were fabricated such that a radiophotoluminescent glass dosimeter (RPLGD) with a Tin filter, namely GD-352M, could be inserted into them. A Tin filter is used to eliminate the overestimated signals in low-energy photons below 100 keV. The measurement uncertainty of the RPLGD reader system based on GD-352M should be analyzed for obtaining reliable protection quantities before using it for practical applications. Generally, the measurement uncertainty of RPLGD systems without Tin filters is analyzed for quality assurance of radiotherapy units using a high-energy photon beam. However, in this study, the measurement uncertainty of GD-352M was analyzed for evaluating the protection quantities. The measurement uncertainty factors in the RPLGD include the reference irradiation, regression curve, reproducibility, uniformity, energy dependence, and angular dependence, as described by the International Organization for Standardization (ISO). These factors were calculated using the Guide to the Expression of Uncertainty in Measurement method, applying ISO/ASTM standards 51261(2013), 51707(2015), and SS-ISO 22127(2019). The measurement uncertainties of the RPLGD reader system with a coverage factor of k = 2 were calculated to be 9.26% from 0.005 to 1 Gy and 8.16% from 1 to 10 Gy. A blind test was conducted to validate the RPLGD reader system, which demonstrated that the readout doses included blind doses of 0.1, 1, 2, and 5 Gy. Overall, the E_n values were considered satisfactory.

• 한국화재소방학회논문지
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• 제33권3호
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• pp.112-120
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• 2019

국내 PBD에서 화재시뮬레이션을 이용한 안전성 평가의 신뢰성을 개선시키기 위하여, 화재시뮬레이션의 입력변수 및 수치모델의 불확실도가 고려된 ASET의 평가방법에 대한 검토가 수행되었다. 이를 위해 영화관 및 오피스텔이 검토 대상으로 선정되었다. 주요 결과는 다음과 같다. 인명안전기준에 제시된 주요 물리량에 가장 큰 영향을 미치는 열발생률의 불확실도를 고려할 때, 온도, CO 및 가시도의 상당한 변화가 발생됨을 확인하였다. 또한 수치모델의 불확실도를 반영한 편향인자를 고려할 때, 온도 및 CO는 큰 변화가 없으나 FDS의 낮은 연기농도 예측성능으로 인하여 가시도는 크게 증가됨을 알 수 있었다. 마지막으로 국내 PBD에서 ASET이 대부분 가시도에 의해 결정되는 원인이 논의되었으며, 정확한 ASET 평가를 위해 화재시뮬레이션의 입력변수 및 수치모델의 불확실도 적용 방안이 제안되었다.

• 한국전문물리치료학회지
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• 제23권2호
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• pp.93-99
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• 2016

Background: Parametric statistical procedures are typically conducted under the condition in which a sample distribution is statistically identical with its population. In reality, investigators use inferential statistics to estimate parameters based on the sample drawn because population distributions are unknown. The uncertainty of limited data from the sample such as lack of sample size may be a challenge in most rehabilitation studies. Objects: The purpose of this study is to review the bootstrapping method to overcome shortcomings of limited sample size in rehabilitation studies. Methods: Articles were reviewed. Results: Bootstrapping method is a statistical procedure that permits the iterative re-sampling with replacement from a sample when the population distribution is unknown. This statistical procedure is to enhance the representativeness of the population being studied and to determine estimates of the parameters when sample size are too limited to generalize the study outcome to target population. The bootstrapping method would overcome limitations such as type II error resulting from small sample sizes. An application on a typical data of a study represented how to deal with challenges of estimating a parameter from small sample size and enhance the uncertainty with optimal confidence intervals and levels. Conclusion: Bootstrapping method may be an effective statistical procedure reducing the standard error of population parameters under the condition requiring both acceptable confidence intervals and confidence level (i.e., p=.05).

• 전기학회논문지
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• 제62권11호
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• pp.1617-1620
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• 2013

The widely-used measurement methods for conductivity of non-magnetic metals are van der Pauw method, Two Point Probe method and Eddy Current method. Among them a more simpler and easier method is the Eddy Current method and an instrument using the method is a Conductivity Meter which can measure a conductivity by contacting its probe on a sample surface. However, conductivity standards are essentially needed to confirm the meter's performance or to calibrate it. In this study, six kinds of the standards which are made of Cu, Al-1, Al-2, brass, Zn and SUS-316 are developed and conductivity ranges for the standards are 2.27 %IACS ~ 101.6 %IACS with measurement uncertainty of less than 0.3 %.