• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.4
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• pp.405-418
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• 2019

Based on spent fuels characteristics from domestic nuclear power plants and a disposal scenario from the current basic plan for high-level radioactive waste management, an improved disposal system has been proposed that enhances disposal efficiency and economic effectiveness compared to the existing disposal system. For this purpose, two disposal canisters concepts were derived from the length of the spent fuel generated from the nuclear power plants. In the disposal scenario, the acceptable amount of decay heat for each disposal container was determined, taking into account the discharge and disposal times of spent fuels in accordance with the current basic plan. Based on the determined decay heat of the two types of disposal canisters and the associated disposal system, thermal stability analyses were performed to confirm their suitability to the proposed disposal system design requirement and disposal efficiency assessment. The results of this study confirm 20% reduction in the disposal area and 20% increase in disposal density for the proposed disposal system compared to the existing system. These results can be used to establish a spent fuel management policy and to design a viable commercial disposal system.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.339-346
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• 2018

A geological repository system consists of a disposal canister with packed spent fuel, buffer material, backfill material, and intact rock. The buffer is indispensable to assure the disposal safety of high-level radioactive waste. Since the heat generated from spent nuclear fuel in a disposal canister is released to the surrounding buffer materials, the thermal properties of the buffer material are very important in determining the entire disposal safety. Especially, since thermal expansion can cause thermal stress to the intact rock mass in the near-field, it is very important to evaluate thermal expansion characteristics of bentonite buffer materials. Therefore, this paper presents a thermal expansion coefficient prediction model of the Gyeongju bentonite buffer materials which is a Ca-bentonite produced in South Korea. The linear thermal expansion coefficient was measured considering heating rate, dry density and temperature variation using dilatometer equipment. Thermal expansion coefficient values of the Gyeongju bentonite buffer materials were $4.0{\sim}6.0{\times}10^{-6}/^{\circ}C$. Based on the experimental results, a non-linear regression model to predict the thermal expansion coefficient was suggested and fitted according to the dry density.

• Journal of the Korean Geophysical Society
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• v.1 no.1
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• pp.41-50
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• 1998

Schlumberger soundings, dipole-dipole survey and electrical conductivity mappings were carried out inside and in front of the entrance of the Okmyung waste landfill in August, 1997 and January, 1998. Inside and in front of the landfill, 11 and 4 electrical soundings and 1 dipole-dipole survey were carried out, respectively. Electrical conductivities were measured at 164 points along the 4 lines in front of the entrance of the landfill. Interpretations of survey data show that low resistivity zones of 0.3∼3 Ωm extend down to 65 m depth from the surface in the 6th landfill, which indicates subsurface contamination by leachate and leachate level at 3∼6 m depth from the surface. In the 9th landfill, low resistivity zones below 2 Ωm appear at 11∼15 m depth from the surface, which indicates a very slim chance of subsurface contamination. On the other hand, electrical surveys and electrical conductivity mappings reveal low resistivities at shallow depths in front of the entrance of the landfill, indicating a high possibility of contamination of weathered zone in this area. It appears that southern part of this area close to the 6th landfill is more contaminated by leachate.

• Nuclear Engineering and Technology
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• v.45 no.6
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• pp.731-744
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• 2013

Energy security is a topic of high importance to many countries throughout the world. Countries with access to vast energy supplies enjoy all of the economic and political benefits that come with controlling a highly sought after commodity. Given the desire to diversify away from fossil fuels due to rising environmental and economic concerns, there are limited technology options available for baseload electricity generation. Further complicating this issue is the desire for energy sources to be sustainable and globally scalable in addition to being economic and environmentally benign. Nuclear energy in its current form meets many but not all of these attributes. In order to address these limitations, TerraPower, LLC has developed the Traveling Wave Reactor (TWR) which is a near-term deployable and truly sustainable energy solution that is globally scalable for the indefinite future. The fast neutron spectrum allows up to a ~30-fold gain in fuel utilization efficiency when compared to conventional light water reactors utilizing enriched fuel. When compared to other fast reactors, TWRs represent the lowest cost alternative to enjoy the energy security benefits of an advanced nuclear fuel cycle without the associated proliferation concerns of chemical reprocessing. On a country level, this represents a significant savings in the energy generation infrastructure for several reasons 1) no reprocessing plants need to be built, 2) a reduced number of enrichment plants need to be built, 3) reduced waste production results in a lower repository capacity requirement and reduced waste transportation costs and 4) less uranium ore needs to be mined or purchased since natural or depleted uranium can be used directly as fuel. With advanced technological development and added cost, TWRs are also capable of reusing both their own used fuel and used fuel from LWRs, thereby eliminating the need for enrichment in the longer term and reducing the overall societal waste burden. This paper describes the origins and current status of the TWR development program at TerraPower, LLC. Some of the areas covered include the key TWR design challenges and brief descriptions of TWR-Prototype (TWR-P) reactor. Selected information on the TWR-P core designs are also provided in the areas of neutronic, thermal hydraulic and fuel performance. The TWR-P plant design is also described in such areas as; system design descriptions, mechanical design, and safety performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.193-203
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• 2011

The purpose of this study, looking to which the recycled fine aggregates from waste concrete have a lot of problems as a material for structure purpose, is applying the recycled fine aggregate to Self-Compacting Concrete(In the reminder of this paper, it often referred to as SCC) by using the characteristic which the powder containing the recycled fine aggregates can increase strength and liquidity. In this study, that is, the recycled fine aggregate powder is appropriate for developing high strength(over 40 MPa) and liquidity(JSCE 2 grade), the characteristic of the SCC and it was increased the ratio of mixing the recycled fine aggregates emerging from waste concrete and the normal fine aggregates by 25%, making differential in total 5 levels and applied to SCC. After all, this study was reviewed the physical properties of the fresh concrete, analyzed the mechanical properties and durability of the hardening concrete and tried to ensure the possibility of utilizing the recycled fine aggregates as a material for SCC. As a result, this study reached a conclusion that among the 5-level replacement ratios of the physical, mechanical analysis and the durability characteristics, the normal fine aggregates could be applied up to a replacement ratio of 50% more than the recycled fine aggregates and resulted in a deterioration in performance the replacement ratio larger than 50%. It is judged that the applicability of the real structures should be followed up in order to check the possibility of applying the recycled fine aggregates to real life.

• Journal of the Korea Organic Resources Recycling Association
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• v.2 no.1
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• pp.31-40
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• 1994

In the later part of 1980's, a great emphasis has been placed on the treatment issues of livestock wastes due to the continuous increase in consumption of livestock and meat products. Continued economic development for three decades has enhanced the nationally general level of life for the purpose of exit out of absolute poverty, thus accompanied with people's demand for a quality of environment beyond the traditional economic factors over times. Such an individual or collective demand for environment of life has been primarily focussed and argued on only rural environment in the early development periods. In perspective of clean water supply and security for urban area, however, it is more important to treat livestock wastes in the oriented-sustainable environment than in the conventional ways without working on environment degradation. Livestock wastes composed of the high-concentrated organic matter ought to be controlled and treated in sound ways, if not, which on one hand may result in pollution of underground water, surface water and a nasty smell, and on the other hand also may cause people to file a civil petition. Therefore on the research paper, reviewing occurrence of livestock waste and situation of treatment in details, through scrutinizing the government regulation and financing or subsidizing for it, author intends to find out the initiative of 'resourcefication' of treating of livestock wastes in the environmental soundness and efficiency

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.6 no.2
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• pp.101-109
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• 2008

For the Kyungju bentonite which is considered as a candidate material for the buffer and backfill in the high-level waste repository, the thermal conductivities of compacted bentonite and a bentonite-sand mixture were measured. The thermal conductivities of the compacted bentonites with a dry density of 1.2 to $1.8\;Mg/m^3$ and the bentonite-sand mixture with a dry density of 1.6 and $1.8\;Mg/m^3$ were measured within the gravimetric water content range of 10wt% to 20wt% and the sand fraction range of 10 to 30wt%. The thermal conductivity of compacted bentonite and a bentonite-sand mixture increases with increasing dry density and sand weight fraction in the case of constant water weight fraction, and increases with increasing water weight fraction and sand weight fraction in the case of constant dry density. The empirical correlations to describe the thermal conductivity of compacted bentonite and a bentonite-sand mixture as a function of water fraction at each dry density were suggested. These correlations can predict the thermal conductivities of bentonite and a bentonite-sand mixture with a difference below 10%.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.17 no.3
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• pp.329-338
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• 2019

Suction of unsaturated bentonite buffers is a very important input parameter for hydro-mechanical performance assessment and design of an engineered barrier system. This study analyzed suction measurement techniques and constitutive models of unsaturated porous media reported in the literature, and suggested suction measurement techniques and constitutive models suitable for bentonite buffer in an HLW repository. The literature review showed the suction of bentonite buffer to be much higher than that of soil, as measured by total suction including matric suction and osmotic suction. The measurement methods (RH-Cell, RH-Cell/Sensor) using a relative humidity sensor were suitable for suction measurement of the bentonite buffer; the RH-Cell /Sensor method was more preferred in consideration of the temperature change due to radioactive decay heat and measurement time. Various water retention models of bentonite buffers have been proposed through experiments, but the van Genuchten model is mainly used as a constitutive model of hydro-mechanical performance assessment of unsaturated buffers. The water characteristic curve of bentonite buffers showed different tendencies according to bentonite type, dry density, temperature, salinity, sample state and hysteresis. Selection of water retention models and determination of model input parameters should consider the effects of these controlling factors so as to improve overall reliability.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1636-1639
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• 2005

The process equipment and remote handling for the deep geological disposal of high-level radioactive waste(HLW) should be checked prior to the operation in view of reliability and operability. In this study, the concept of virtual environment workcell is implemented to analyze and define the feasible disposal process instead of real mock-up, which is very expensive and time consuming. To do this, the parts of process equipment for the disposal and maintenance will be modeled in 3-D graphics, assembled, and kinematics will be assigned. Also, the virtual workcell for the encapsulation and disposal process of spent fuel will be implemented in the graphical environment, which is the same as the real environment. This virtual workcell will have the several functions for verification such as analyses for the equipment's work space, the collision detection, the path planning and graphic simulation of the processes etc. This graphic virtual workcell of the HLW disposal process can be effectively used in designing of the processes for the hot cell equipment and enhance the reliability of the spent fuel management.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.4
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• pp.415-422
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• 2008

The emission characteristics of odorous compounds discharged from the major environmental treatment facilities in Chungju were closely investigated by an ammonia passive sampler and by analyzing a questionnaire of the public complains. Amongst the four major emission sources, the manure treatment facility showed the highest concentration. The major components were sulfur compounds including H$_2$S, tri-methyl amine, and aldehydes. The foodwaste treatment processes releases sulfur compounds and aldehydes. Municipal waste water treatment facility emits a high concentration of acetaldehyde. It was found that the perceived odor level depends on the meteorological condition, and the odor intensity was higher at midnight than daytime.