• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.3
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• pp.179-189
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• 2014

Pyroprocessing has been developed for the purpose of resolving the current spent nuclear fuel management issue and enhancing the recycle of valuable resources. An electrolytic reduction of the pyroprocessing is a process to reduce oxides into metals using LiCl as an electrolyte and requires a post-treatment process due to the inclusion of residual salt in porous metal products. A vacuum distillation has been adopted for various molten salt systems and could be applied to the post-treatment process of the electrolytic reduction. The residual salt in the metal products includes LiCl, alkali chlorides, and alkaline earth chlorides. In this paper, vapor pressures of chlorides have been estimated and the composition changes on the residual liquid during the vacuum distillation process have been calculated. A model combining a material balance and vapor-liquid equilibrium relations has been proposed under a constant vapor discharging flow rate and liquid composition changes have been calculated using the vapor pressures with respect to a dimensionless time. The behaviors have been compared with temperature and molten salt composition changes to simulate the process condition variation. The distillation of the residual salt has been dominated by LiCl which is the main component of the salt and CsCl of which vapor pressure is higher than that of LiCl would be readily removed. RbCl exhibits similar vapor pressure with LiCl and maintains its composition. However, $SrCl_2$ and $BaCl_2$ of which vapor pressures are much lower than that of LiCl are concentrated with time and expected to be possibly precipitated during the distillation when the initial compositions are increased.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.353-357
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• 2017

In this study, the inclusion phenomena of tetrahydrofuran + 3-hydroxytetrahydrofuran + $CH_4$ clathrate hydrates were explored via thermodynamic and spectroscopic approaches. The phase equilibria of the double hydrates - THF + $CH_4$ and 3-OH THF + $CH_4$ clathrate hydrates - were determined by pressure-temperature trace during hydrate formation and dissociation, and the result revealed that the equilibrium pressures were shifted to lower pressure region compared to pure $CH_4$ hydrate. The powder X-ray diffraction patterns revealed that the double hydrates of THF + 3-OH THF formed structure II type clathrate hydrates with $CH_4$. The dispersive Raman spectra of the double clathrate hydrates also exhibited that $CH_4$ can be trapped in both $5^{12}6^4$ and $5^{12}$ cages whereas THF and 3-OH THF were encaged in $5^{12}6^4$ cage.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.114-130
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• 1999

It is very important to study on the structural behaviors of structurally damaged tunnel linings. A series of centrifuge model tests were performed in order to investigate different behaviors of tunnel linings. A 1/100-scaled aluminum horseshoe tunnel linings with a radius 5 cm, height 8 cm were buried in a depth with dry Joomunjin standard sand, the relative density of which was 86%. Such sectional forces as bending moments and thrusts along the tunnel circumference were measured by twelve strain gages. Earth pressures in soil mass and on the outside of lining model were estimated by pressure transducers, ground surface settlements at a center and edges by using LVDTs.

• Journal of Environmental Science International
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• v.21 no.2
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• pp.189-202
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• 2012

Power spectral analysis for $PM_{10}$ observed at 10 cities in the Korean Peninsula from 2004 to 2010 was carried out to examine the spatial and temporal features of $PM_{10}$ evolution cycle. The power spectrum analysis proposed 9 typical cycles (0.5 day, 1day, 5.4day, 8~10day, 19~21day, 26day, 56day, 180day and 365day) for $PM_{10}$ evolution and the cycles are strongly associated with dilution and transportation due to the meterological influence. The spectrum intensity of 5.4day and 26day $PM_{10}$ evolution cycles mainly depend on the advection cycles of synoptic pressures system and long-term variation of climatological forcing, respectively. The intensity of $PM_{10}$ evolution with longer temporal cycles than one day tends to be stronger in La ni$\tilde{n}$a period in comparison with that in El ni$\tilde{n}$o period. Mean of typical intensity of $PM_{10}$ evolution in La ni$\tilde{n}$a period estimated to be 30% larger than El ni$\tilde{n}$o period. Thus the global scale meteorological phenomena such as El ni$\tilde{n}$o and La ni$\tilde{n}$a also can influence the variation of wind system in the Korean Peninsula and $PM_{10}$ evolution. but global scale forcing tends to influence different manner for $PM_{10}$ evolution in accordance with its temporal cycles.

• Geotechnical Engineering
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• v.13 no.4
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• pp.135-148
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• 1997

Coulomb's theory has been usually used in practice to obtain lateral earth pressure against retaining wall. Such theory is based in the assumption that the lateral pressure is a tai angular distribution, since the point of applying the lateral thrust cannot be obtained by using it. However, the results of laboratory and field tests showed that the lateral pressure was not a triangular but a nonlinear distribution. To overcome the drawback of the Coulomb's theory, the different theoretical approaches(Handy, 1985. Kingsley, 1989 : Kellogg, 1993, Chung et at,1993, 1996a) were performed for gravity wall backfilled by cohesionless soil. On the other hand, for retaining wall backfilled by ,cohesive soil, theoretical analyses were carried out only on the basis of the Rankine's or Coulomb's concepts, but the equations showed different results. Here was newly derived the equations of lateral pressures under undrained condition against gravity wall backfilled by cohesive soil. They were based on the Coulomb's wedge, adopted the arching concept. Some of the equations were derived by neglecting tension crack, while the others by considering it. Comparative results for applying different examples showed that the equation considering tension crack might be reasonable.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.119-127
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• 2017

This paper presents a study of reinforced earth model wall reinforced by geosynthetics subjected to vertical surcharge. 7 types of reinforced earth model wall were constructed in the model box($100cm{\times}140cm{\times}100cm$) to assess the deformation and stress behavior of model walls according to different tensile strength and laying number of reinforcement and surcharge pressures. 3 types of geosynthetics that have different tensile strength were used as reinforcement. The test was carried out by changing the number of reinforcement to 5, 7, 9, and surcharge pressure to 50, 100, 150, 200, 250 kPa. The model test found that the maximum lateral displacements occurred at the 0.7 H (H : Wall height) position from the bottom of the model wall and vertical stress was low in the smaller surcharge pressure and the larger tensile strength of reinforcement.

• Smart Structures and Systems
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• v.15 no.3
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• pp.769-785
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• 2015

Although timber structures have been extensively used in underground temporary supporting system, their actual performance is poorly understood, resulting in potentially conservative and over-engineered design. In this paper, a novel wireless sensor technology, SmartPlank, is introduced to monitor the field performance of timber structures during underground construction. It consists of a wooden beam equipped with a streamlined wireless sensor node, two thin foil strain gauges and two temperature sensors, which enables to measure the strain and temperature at two sides of the beam, and to transmit this information in real-time over an IPv6 (6LowPan) multi-hop wireless mesh network and Internet. Four SmartPlanks were deployed at the London Underground's Tottenham Court Road (TCR) station redevelopment site during the Stair 14 excavation, together with seven relay nodes and a gateway. The monitoring started from August 2013, and will last for one and a half years until the Central Line possession in 2015. This paper reports both the short-term and long-term performances of the monitored timber structures. The grouting effect on the short-term performance of timber structures is highlighted; the grout injection process creates a large downward pressure on the top surface of the SmartPlank. The short and long term earth pressures applied to the monitored structures are estimated from the measured strains, and the estimated values are compared to the design loads.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2017.10a
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• pp.74-74
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• 2017

Electrorefining is a key step in pyroprocessing. The electrorefining process is generally composed of two recovery steps - the deposit of uranium onto a solid cathode and the recovery of the remaining uranium and TRU elements simultaneously by a liquid cadmium cathode. Uranium deposit recovered from the solid cathode is a dendritic powder. It is necessary to separate the adhered salt from the deposits prior to the consolidation of uranium deposit. The adhered salt is composed of lithium, potassium, uranium, and rare earth chlorides. Distillation process was employed for the cathode processing. One of the operation methods is distillation of the salt at low temperature ($900^{\circ}C$), and then melting of the deposit at high temperature to avoid a backward reaction. For the development of the salt distiller, the distillation behavior of the low vapor pressure chlorides should be studied. Rare earth chlorides in the adhered salt of uranium deposits have relatively low vapor pressures compared to the process salt (LiCl-KCl). In this study, the evaporation rates of the lanthanum and neodymium chlorides were measured for the salt separation from electrorefiner uranium deposits in the temperature range of $825{\sim}910^{\circ}C$. The evaporation rate of both chlorides increased with an increasing templerature. The evaporation rate of lanthanum chloride varied from 0.12 to $1.68g/cm^2/h$. Neodymium chloride was more volatile than lanthanum chloride. The evaporation rate of neodymium chloride varied from 0.20 to $4.55g/cm^2/h$. The evaporation rate of both chlorides are more than $1g/cm^2/h$ at $900^{\circ}C$. Even though the evaporation rates of both chlorides were less than that of the process salt, the contents of the lanthanide chlorides were small in the adhered salt. Therefore it can be concluded that $900^{\circ}C$ is suitable for the operation temperature of the salt distiller.

• Journal of the Korean GEO-environmental Society
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• v.12 no.9
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• pp.27-33
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• 2011

In the case of the existing method of underground pipe construction, the difficulty of the bedding compaction of pipe causes reducing the compaction efficiency and the stability of the underground facilities and conclusively damaging the structures. One of the methods to solve these problem is using the flowable fills as a backfill material. Therefore, in this study, numerical analysis of the underground pipe was performed in order to evaluate the behavior of pipe according to backfill mixtures. To estimate the deformation characteristic of the underground pipe, the displacement of the main part of the pipe, ground settlement and vertical earth pressures were measured in different backfill mixtures and maintaining the other conditions constantly. As a result of numerical analysis, using the flowable fills as the backfill material is better than using sand in reducing the ground settlement, the pipe deformation and the vertical earth pressure aspect.

• Geomechanics and Engineering
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• v.30 no.5
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• pp.401-411
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• 2022

To obtain the dynamic mechanical properties, fracture modes, energy and brittleness characteristics of Furong Baijiao coal rock, the dynamic impact compression tests under 0, 4, 8 and 12 MPa confining pressure were carried out using the split Hopkinson pressure bar. The results show that failure mode of coal rock in uniaxial state is axial splitting failure, while it is mainly compression-shear failure with tensile failure in triaxial state. With strain rate and confining pressure increasing, compressive strength and peak strain increase, average fragmentation increases and fractal dimension decreases. Based on energy dissipation theory, the dissipated energy density of coal rock increases gradually with growing confining pressure, but it has little correlation with strain rate. Considering progressive destruction process of coal rock, damage variable was defined as the ratio of dissipated energy density to total absorbed energy density. The maximum damage rate was obtained by deriving damage variable to reflect its maximum failure severity, then a brittleness index BD was established based on the maximum damage rate. BD value declined gradually as confining pressure and strain rate increase, indicating the decrease of brittleness and destruction degree. When confining pressure rises to 12 MPa, brittleness index and average fragmentation gradually stabilize, which shows confining pressure growing cannot cause continuous damage. Finally, integrating dynamic deformation and destruction process of coal rock and according to its final failure characteristics under different confining pressures, BD value is used to classify the brittleness into four grades.