• Nuclear Engineering and Technology
• /
• v.43 no.6
• /
• pp.523-530
• /
• 2011

In a previous study, the stochastic space-dependent kinetics model (SSKM) based on the forward stochastic model in stochastic kinetics theory and the Ito stochastic differential equations was proposed for treating monoenergetic space-time nuclear reactor kinetics in one dimension. The SSKM was tested against analog Monte Carlo calculations, however, for exemplary cases of homogeneous slab reactors with only one delayed-neutron precursor group. In this paper, the SSKM is improved and evaluated with more realistic and complicated cases regarding several delayed-neutron precursor groups and heterogeneous slab reactors in which the extraneous source or reactivity can be introduced locally. Furthermore, the source level and the initial conditions will also be adjusted to investigate the trends in the variances of the neutron population and fission product levels across the reactor. The results indicate that the improved SSKM is in good agreement with the Monte Carlo method and show how the variances in population dynamics can be controlled.

• Nuclear Engineering and Technology
• /
• v.11 no.3
• /
• pp.219-229
• /
• 1979

The current status of the computational methods and computer codes for the analysis of reactor kinetics is reviewed. Computational methods which have been developed for space-dependent transient analyses are presented and recent progress in the development of methods is discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.37 no.4
• /
• pp.383-391
• /
• 2009

The detonation wave characteristics of JP-7 and oxygen mixture is investigated by one-step induction parameter model (IPM) obtained from a detailed chemistry mechanism. A general procedure of obtaining reliable one-step kinetics IPM for hydrocarbon mixture from the fully detailed chemistry is described in this study. The IPM is obtained by the reconstruction of the induction time database obtained from a detailed kinetics library. The IPM was confirmed by the comparison of the induction time calculations with that from detailed kinetics. The IPM is later implemented to a fluid dynamics code and applied for the numerical simulation of detonation wave propagation. The numerical results show the detailed characteristics of the detonation wave propagation in JP-7 and oxygen mixture at affordable computing time, which is not be possible by the direct application of the detailed chemical kinetics mechanism of hydrocarbon fuel combustion.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.7
• /
• pp.89-96
• /
• 2006

The combustion temperature in gas generator should be kept below around 1,000K to avoid any possible thermal damages to turbine blade by adopting either fuel rich or oxidizer rich combustion. Thus, non-equilibrium chemical reaction dominates in the gas generator. Meanwhile, Kerosene is a compounded fuel mixed with various types of hydrocarbon elements and difficult to model the chemical kinetics. This study focus to model the non-equilibrium chemical reaction of kerosene/LOX with detailed kinetics developed by Dagaut using PSR(Perfectly stirred reactor) assumption. Also, droplet evaporation time is taken into account by calculating for the residence time of droplet and by decoupling reaction temperature from the reactor temperature. In Dagaut’s surrogate model for kerosene, chemical kinetics of kerosene consists of 1592 reaction steps with 207 chemical species. The comparison of calculation results with experimental data could provide very reliable and accurate numbers in the prediction of combustion gas temperature, species fraction and other gas properties.

• Nuclear Engineering and Technology
• /
• v.15 no.2
• /
• pp.98-109
• /
• 1983

A two-step alternating direction explicit method is developed to solve the space-dependent reactor kinetics equations in two space dimensions. As a special case in the general class of alternating direction implicit methods, this method is analysed for accuracy and stability. To test the validity of this method it is compared with the implicit-difference method used in the TWIGL program. It is shown that the two methods are closely related. The time dependent neutron fluxes of the pressurized water reactor (PWR), during control rod insertion, and, of the CANDU-PHW reactor, in case of postulated loss of coolant accident, are obtained from the numerical calculation results.

• Nuclear Engineering and Technology
• /
• v.18 no.2
• /
• pp.71-77
• /
• 1986

A one dimensional neutron kinetics program, BIK which is applicable to the safety analyses of PWR's is developed to analyze the reactor core in axial dimension. The BIK employs the finite difference technique in space and $\theta$-time integration method in time. Detailed models for the Doppler and moderator feedbacks and control rod motion are included. The benchmark of the nuclear model is carried out through the ANL benchmark problem and the time dependent nuclear power change in the rod ejection accident of KNU1 is calculated by BIK code. The results indicate that the BIK can predict the neutron dynamics with fair accuracy within the limits of one dimensional analysis and it is useful for the safety analyses of PWR's.

• Nuclear Engineering and Technology
• /
• v.42 no.3
• /
• pp.259-270
• /
• 2010

New generation nuclear reactors are designed using advanced safety analysis methods. A thorough understanding of different interacting physical phenomena is necessary to avoid underestimation and overestimation of consequences of off-normal transients in the reactor safety analysis results. This feature requires a multiphysics reactor simulation model. In this context, a coupled dynamics model based on a multiphysics formulation is developed indigenously for the transient analysis of large pressurized VVER reactors. Major simplifications are employed in the model by making several assumptions based on the physics of individual phenomenon. Space and time grids are optimized to minimize the computational bulk. The capability of the model is demonstrated by solving a series of international (AER) benchmark problems for VVER reactors. The developed model was used to analyze a number of reactivity transients that are likely to occur in VVER reactors.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.10a
• /
• pp.429-436
• /
• 1997

운전원 훈련용 시뮬레이터의 국산화 개발계획에 따라 영광 원자력 3,4호기 발전소 운전원 훈련용 시뮬레이터가 국내 최초로 개발되었다. STK(space and time kinetics)와 RETACT (Real Time Advanced Core and Thermohydraulics)코드를 이용하여 영광 3,4호기 시뮬레이터의 실시간 NSSS 모델을 생성하였다. 생성된 모델의 검증(Verification Validation)을 위해 정상상태(Steady State)에서의 주요인자들이 ANS3.5의 오차범위이내임을 확인하였다. 과도상태(Transient)의 검증을 위해 터빈정지 과도상태와 주증기 관파열(Main Steam Line Rupture)사고를 실제 발전소 시험 데이터 및 성능해석 코드(NPA)를 이용하여 분석한 결과와 비교하였다. 비교 결과 기준발전소의 반응과 큰 차이 없이 운전원 훈련용 시뮬레이터의 규격인 ANS 3.5를 잘 만족함을 확인 할 수 있었다.

• Korean Journal of Applied Biomechanics
• /
• v.29 no.3
• /
• pp.197-204
• /
• 2019

Objective: The purpose of this study was to identify the effect of high-heels (HH) modification on metatarsal stress in female workers. Method: Seven females who work in clothing stores ($heights=160.4{\pm}3.9cm$; $weights=47.4{\pm}4.1kg$; $age=31.3{\pm}11.1yrs$; $HH\;wear\;career=8{\pm}6.5yrs$) wore two types of HH (original and modified). The modified HH had been grooved with 1.5 cm radius and 0.2 cm depth around the first metatarsal area inside of the shoes using the modified shoe-last. Participants were asked to walk for 15 minutes on a treadmill and to stand for 10 minutes with original and modified HH, respectively. Kinetics data were collected by the F-scan in-shoe system. After each test, participants were asked to rate their perceived exertion using the Borg's 15-grade RPE scale and interviewed about their feeling of HH. Nonparametric Wilcoxon signed-rank test and effect size (Cohen's d) were used to determine the difference of the variables of interest between the original and modified HH. Results: In the present study, modified HH of the peak contact pressure of 1st metatarsal (PCP) left, PCP right, pressure time integral (PTI) left, peak pressure gradient (PPG) left during standing and PPG right during walking are greater than original HH. And even it didn't show statistically significant, the average in all pressure values of modified HH showed bigger than original HH. It surmised to be related to awkward with modified HH. Even though they said to feel the comfortable cause of big space inside of HH in the interview, they seemed to be not enough time to adapt with new HH. So their walking and standing postures were unstable. Conclusion: Modified the fore-medial part of HH can reduce the stress in the first metatarsal head and big toe area during standing and walking.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.11
• /
• pp.2067-2076
• /
• 2000

The experiments have been made to develop manganese-based sorbent(MT, MFT) for the removal of hydrogen sulfide from simulated hot coal gases. Manganese-based sorbents were tested in an ambient-pressure fixed-bed reactor to calculate H2S removal efficiency. and a three hole jet attrition tester to characterize the sorbent physical properties. According to the experimental results of attrition test. the attrition resistance of 5% bentonite containing sorbent was higher than that of 2% bentonite. The attrition resistances of both sorbents increased with induration temperature. Effects of sulfidation temperature. space velocity. and $H_2S$ concentrations on the $H_2S$ removal efficiency were investigated. Experimental results showed that $H_2S$ could be removed from 5,100ppmv to 20ppmv at $450^{\circ}C$, and to 30~65ppmv at $550{\sim}650^{\circ}C$ for both MT/MFT sorbents. As for the change of space velocity, the breakthrough time was decreased with space velocity.