• Proceedings of the KSME Conference
• /
• 2001.06e
• /
• pp.463-468
• /
• 2001

This paper presents the methodology for thermal hydraulic analysis of Pressurized Water Reactor (PWR) steam generators. Topics include porous media approach, governing equations, physical models and correlations for solid-to-fluid interaction and heat transfer and numerical solution scheme. Some details about the ATHOS3 code currently used widely for thermal hydraulic analysis of PWR steam generators in the industry are presented. The ATHOS3 code is applied to the thermal hydraulic analysis of steam generator in the Korea YGN 3&4 nuclear power plant and the computed results are presented.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.1918-1923
• /
• 2009

결정질 암반에서 지하수의 수리적 특성을 파악하기 위해 수행되고 있는 수리시험 방법은 정률법, 정압법, 순간주입(회복)법 등 세 가지로 구분할 수 있다. 본 연구에서 다루는 정압주입시험 (Constant Head Injection Test, CHIT)은 위의 정압법의 한 종류로 토목공학, 지질공학 분야에서 대상 구간의 투수계수 추정을 위해 널리 쓰이는 수리 시험이며, 이는 단일 패커나 이중패커를 이용하여 시험 구간을 격리하고, 격리된 구간에 일정한 압력으로 물을 주입하여 주입되는 물의 양을 파악함으로써, 시험 구간의 수리전도도(Hydraulic conductivity)를 산출하는 전통적인 수리시험이다. 본 연구에서는 수치실험을 통해 시험 구간 및 주입 압력의 크기 등 인위적인 요인에 의해 도출되는 투수계수가 어떻게 달라지는지에 대해 평가해 보았다. 일반적으로 단열 암반에서 수행한 정압주입시험의 해석에 있어 매질을 균질, 등방성 다공질이라는 가정으로 구간별 투수량계수를 산출하기 때문에, 다공성 매질의 지하수 유동을 모사하는 MODFLOW를 수치모사 코드로서 이용하였다. 시험구간의 크기 및 주입압력에 대한 민감도 분석 결과, 시험구간의 크기에 상관없이 수치모의에서 입력한 수리전도도 값에 비해 낮은 수리전도도 값이 산출되었으며, 주입 압력이 클수록 산출되는 수리전도도 값이 매질의 수리전도도 값과 차이가 났다. 민감도 분석 결과 현장수리시험에서 정압 주입시험에 의한 구간별 수리전도도 산출함에 있어 시험구간의 크기와 주입 압력 값에 대하여 고려해야 한다고 판단된다.

• The Journal of Engineering Geology
• /
• v.19 no.1
• /
• pp.71-79
• /
• 2009

Step-drawdown tests were conducted at four pumping Wells, two in porous media and two in fractured rocks, respectively. In general, P = 2.0 suggested by Jacob (1947) is applied to porous media and fractured rocks in terms of drawdowns of step-drawdown test. In an attempt to review problems of linear model (Jacob's graphic method) in interpreting the step-draw down test, the outcomes of well parameters (aquifer loss coefficient (B), well loss coefficient (C) and well loss exponent (P)) calculated from linear and nonlinear model (Labadie and Helweg's least-squares method) were compared and analyzed. The values of C and P calculated from linear and nonlinear models differed according to permeability of aquifer and the conditions of pumping well. The value C obtained from nonlinear models in porous media and fractured rocks is about $10^0{\sim}10^{-2}$ and $10^{-3}{\sim}10^{-6}$ times lower than in their linear models, respectively. The value P of porous media obtained from nonlinear model ranged from 2.123 to 2.775, while it ranged from 3.459 to 5.635 for fractured rocks. In case of nonlinear model, well loss highly depends on the value P. At this time, well efficiencies calculated from linear and nonlinear models were $1.56{\sim}14.89%$ for porous media and $8.73{\sim}24.71%$ for fractured rocks, showing a significant error according to chosen models. In nonlinear model, it was found that the regression analysis using the least squares method was very useful to interpret step-drawdown test in all aquifer.

• Proceedings of the KIEE Conference
• /
• 2003.07c
• /
• pp.1938-1940
• /
• 2003

본 연구는 요소 센서 제작을 위한 과정으로서, 전기화학적 방법을 이용한 다공질 실리콘 구조 형성과, PDV(Physical Vapor Deposition) 법에 의한 백금 박막 코팅 및 전기화학적 전도성 고분자 코팅과 urease 고정화 단계를 고찰하고 감도 특성을 제시 하였다. 전극 기질로서 B을 도우핑한 p-type 실리콘웨이퍼를 사용하였고, HF:$C_2H_5OH:H_2O$=1:2:1의 부피비를 갖는 에칭 용액에서 5분간 -7 $mA/cm^2$의 일정 전류를 가하여 폭 2 ${\mu}m$, 깊이 10 ${\mu}m$의 다공질 실리콘(PS) 충을 형성하였다. 그 위에 200 ${\AA}$의 Ti 층을 underlayer로서 증착하고, 2000 ${\AA}$의 Pt를 중착하여 PS/Pt 박막 전극을 제작하고, 전도성 고분자로서 polypyrrole (PPy), 또는 poly(3-mehylthiophene) (P3MT)을 전기화학적으로 코팅한 후, urease(EC 3.5.1.5, type III, Jack Bean, Sigma)를 고정화 하였다. 고정화 시 전해질 수용액의 pH는 7.4로 하여 urease표면이 음전하를 갖도록 하고, 전극에 0.6 V (vs. SCE(Saturated Calomel Electrode))의 일정 전압을 가함으로써 urease가 전도성 고분자 표면에 전기적으로 흡착되도록 하였다. 이상의 방법으로 제작한 요소 센서의 감도는 PPy와 P3MT를 전자 전달 매질로 사용한 경우, 각각 8.44 ${\mu}A/mM{\cdot}cm^2$와 1.55 ${\mu}A/mM{\cdot}cm^2$의 감도를 보였다.

• Journal of computational fluids engineering
• /
• v.17 no.4
• /
• pp.41-48
• /
• 2012

A numerical analysis of thermal stratification in the upper plenum of the MONJU fast breeder reactor was performed. Calculations were performed for a 1/6 simplified model of the MONJU reactor using the commercial code, CFX-13. To better resolve the geometrically complex upper core structure of the MONJU reactor, the porous media approach was adopted for the simulation. First, a steady state solution was obtained and the transient solutions were then obtained for the turbine trip test conducted in December 1995. The time dependent inlet conditions for the mass flow rate and temperature were provided by JAEA. Good agreement with the experimental data was observed for steady state solution. The numerical solution of the transient analysis shows the formation of thermal stratification within the upper plenum of the reactor vessel during the turbine trip test. The temporal variations of temperature were predicted accurately by the present method in the initial rapid coastdown period (~300 seconds). However, transient numerical solutions show a faster thermal mixing than that observed in the experiment after the initial coastdown period. A nearly homogenization of the temperature field in the upper plenum is predicted after about 900 seconds, which is a much shorter-term thermal stratification than the experimental data indicates. This discrepancy is due to the shortcoming of the turbulence models available in the CFX-13 code for a natural convection flow with thermal stratification.

• The Journal of Engineering Geology
• /
• v.14 no.3 s.40
• /
• pp.301-311
• /
• 2004

This study is suggested a new dielectric tracer test method to understand geological structure of porous media and groundwater flow to use the dielectric constant which is one of electrical special quality of various geological materials. To measure their parameters, tracer material is made an ethanol mixing liquid(EML) having a same specific gravity of water. Also, soil materials are prepared a dielectric tracer test using the FDR system that could measure dielectric constant for saturated standard sand and river sand layers which have different initial porosity. To compare with their results, we discussed with the concentration variation of saline water having a saline concentration $3\%$ which is general tracer material by using the electro multi-meter system in the laboratory or field test. In two tracer experiment results, EML tracer test could confirm definitely EML concentration variation from each saturated soil layer as standard and river sands. However, tracer test of saline water $3\%$ concentration could not confirm permeating movement of water by degree of salinity change because these are settled at lower part column in a whole column area continuously. These causes are that specific gravity of saline water is heavier than water. That is, it could know that deposition of saline water is composed of lower part of soil column continuously independently of the direction of water into saturated soil material.

• Geophysics and Geophysical Exploration
• /
• v.18 no.4
• /
• pp.223-231
• /
• 2015

Self-potential (SP) is sensitive to groundwater flow and there are many causes to generate SP. Among many mechanisms of SP, pore-fluid flow in porous media can generate potential without any external current source, which is referred to as electrokinetic potential or streaming potential. When calculating SP responses on the surface due to geothermal fluid within an engineered geothermal system (EGS) reservoir, SP anomaly is usually considered to be generated by fluid injection or production within the reservoir. However, SP anomaly can also result from geothermal water fluid within EGS reservoirs experiencing temperature changes between injection and production wells. For more precise simulation of SP responses, we developed an algorithm being able to take account of SP anomalies produced by not only water injection and production but also the fluid of geothermal water, based on three-dimensional finite-element-method employing tetrahedron elements; the developed algorithm can simulate electrical potential responses by both point source and volume source. After verifying the developed algorithm, we assumed a simple geothermal reservoir model and analyzed SP responses caused by geothermal water injection and production. We are going to further analyze SP responses for geothermal water in the presence of water production and injection, considering temperature distribution and geothermal water flow in the following research.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.10 no.1
• /
• pp.1-11
• /
• 2012

The equation of the step-drawdown test "$s_w=BQ+CQ^p$" written by Rorabaugh (1953) is suitable for drawdown increased non-linearly in the fractured rocks. It was found that value of root mean square error (RMSE) between observed and calculated drawdowns was very low. The calculated $C$ (well head loss coefficient) and $P$ (well head loss exponent) value of well head losses ($CQ^p$) ranged $3.689{\times}10^{-19}{\sim}5.825{\times}10^{-7}$ and 3.459~8.290, respectively. It appeared that the deeper depth in pumping well the larger drawdowns due to pumping rate increase. The well head loss in the fractured rocks, unlike that in porous media, is affected by properties of fractures (fractures of aperture, spacing, and connection) around pumping well. The $C$ and $P$ value in the well head loss is very important to interpret turbulence interval and properties of high or low permeability of fractured rock. As a result, regression analysis of $C$ and $P$ value in the well head losses identified the relationship of turbulence interval and hydraulic properties. The relationship between $C$ and $P$ value turned out very useful to interpret hydraulic properties of the fractured rocks.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.1
• /
• pp.93-107
• /
• 2013

Thermal conduction of the particulate composites or granular materials can be widely used in porous materials and geotechnical engineering. And it has continued to develop "effective thermal conductivity" of medium by modeling energy relationship among particles in medium. This study focuses on the development of the effective thermal conductivity at the unsaturated conditions of soils using the modified network model approach assisted by synthetic 3D random packed systems (DEM method, Discrete Element Method) at the particle scale. To verify the network model, three kinds of glass beads and the Jumunjin sand are used to obtain experimental values at various unsaturated conditions. The PPE (Pressure Plate Extractor) test is then performed to obtain SWCC (Soil-Water Characteristic Curve) of soil samples. In the modified network model, SWCC is used to adjust the equivalent radius of thermal cylinder at contact area between particles. And cutoff range parameter to define the effective zone is also adjusted according to the SWCC at given conditions. From a series of laboratory tests and the proposed network model, the modified network model which adopts a SWCC shows a good agreement in modeling thermal conductivity of granular soils at given conditions. And an empirical correlation between the fraction of the mean radius (${\chi}$) and thermal conductivity at given saturated condition is provided, which can be used to expect thermal conductivity of the granular soils, to estimate thermal conductivity of granular soils.