• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.1
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• pp.23-34
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• 2004

To validate the previous conceptual design of cover system, construction of the engineered barrier test facility is completed and the performance tests of the disposal cover system are conducted. The disposal test facility is composed of the multi-purpose working space, the six test cells and the disposal information space for the PR center. The dedicated detection system measures the water content, the temperature, the matric potential of each cover layer and the accumulated water volume of lateral drainage. Short-term experiments on the disposal cover layer using the artificial rainfall system are implemented. The sand drainage layer shows the satisfactory performance as intended in the design stage. The artificial rainfall does not affect the temperature of cover layers. It is investigated that high water infiltration of the artificial rainfall changes the matric potential in each cover layer. This facility is expected to increase the public information about the national radioactive waste disposal program and the effort for the safety of the planned disposal facility.

• The Journal of Engineering Geology
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• v.9 no.2
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• pp.89-100
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• 1999

This study was carried out to assess the physicochemical properties of domestic bentonites and zeolites from Tertiary Formation as the candidate material for a engineered barrier of a radioactive waste repository. Natural bentonite and zeolite samples were collected from nine bentonite mines and six zeolite mines in Yeonil-Gampo area. The commercial products of bentonite and zeolite were obtained from local companies. The collected samples were investigated to study the following physicochemical properties: X-ray diffraction patterns, swelling, cation exchange capacity(CEC), specific surface area, montmorillonite content, pH, organic carbon content, thermal property, microstruciure and chemical composition. Based on the physicochemical properties of bentonite and zeolite, the bentonites from U-41 and G-46 mines and the zeolites from Daedo and Y-1 mines are regarded as the most desirable candidate materials.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.2
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• pp.123-131
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• 2021

The buffer is a key component of an engineered barrier system that safeguards the disposal of high-level radioactive waste. Buffers are located between disposal canisters and host rock, and they can restrain the release of radionuclides and protect canisters from the inflow of ground water. Since considerable heat is released from a disposal canister to the surrounding buffer, the thermal conductivity of the buffer is a very important parameter in the entire disposal safety. For this reason, a lot of research has been conducted on thermal conductivity prediction models that consider various factors. In this study, the thermal conductivity of a buffer is estimated using the machine learning methods of: linear regression, decision tree, support vector machine (SVM), ensemble, Gaussian process regression (GPR), neural network, deep belief network, and genetic programming. In the results, the machine learning methods such as ensemble, genetic programming, SVM with cubic parameter, and GPR showed better performance compared with the regression model, with the ensemble with XGBoost and Gaussian process regression models showing best performance.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.4
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• pp.273-281
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• 2007

Hyperalkaline groundwater formed by groundwater-cement components and its reaction with bedrock in a nuclear waste repository were simulated by geochemical modeling. The result of groundwater-cement components reaction showed that the pH of water was 13.3 and the precipitated minerals were Brucite, Katoite, Calcium Silicate Hydrate(CSH1.1), Ettringite, Hematite, and Portlandite. The result of interaction between such minerals and groundwater sampled in Gyeongju area also showed that the pH of groundwater reached 12.4. Interaction between such hyperalkaline groundwater and granite was simulated by kinetic model during $10^3$ years. This result showed that the final pH of groundwater reached 11.2 and the variation of pH was controlled by dissolution/precipitation of silicate and CSH minerals. Groundwater quality was also determined by dissolution/precipitation of silicate, CSH, oxide minerals. Our results show that geochemical modeling of long-term hyperalkaline groundwater and rock interaction can contribute to the safety assessment of engineered barrier by predicting geochemical condition in repository site.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.6
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• pp.603-612
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• 2006

The study with laboratory sandbox model has been carried out to address potential use of reclaimed water, as a way for artificially recharging the coastal aquifer, to effectively prevent from seawater intrusion. To do this, we assessed hydraulic and geochemical properties depending upon various extraction and recharging conditions. While solely being recharged, the intrusion could be significantly retarded than those of recharge and extraction implied together. At 0.5 to 2 for the ratio of the extraction over the recharge rate, the fresh water was exploited from the tank, where the void regime was simultaneously saturated with the recharged water. In the meantime, the saline water zone was diluted and back-tracked by the recharged water due to forming a hydraulic geochemical barrier around the injection well. However, if the ratio was being increased to greater than 4, saltwater more deeply intruded to the freshwater zone because the artificial recharge was not sufficiently supplied to timely back-fill the void space. When the aquifer water was intermittently extracted at the ratio of $0.5{\sim}2$ over the recharge rate, the value of S.M.I. decreased, but increasing it to more than 4 unlikely escalated the value of S.M.I as much as $3{\sim}47%$ indicating that the salt water intruded. It finally revealed that the proper ratio of extraction/recharge or intermittent extraction would efficiently retracted seawater intrusion while the freshwater sources could be conservatively utilized.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.1
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• pp.37-43
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• 2014

A parametric sensitivity to the annual exposure dose rate to the farming exposure group has been deterministically carried out for three principal elements identified in the near-field of the pyroprocessed waste repository system as a series study of Part 1 of the coupled paper with the same title. Credit time for both metal and ceramic containers, annual nuclide release rete and the degree of loss of bentonite buffer around the container are selected and investigated deterministically for important nuclides. To this end the A-KRS has been assessed and then compared among each other with the normal, the worst, and the best case scenarios associated with their extreme values these elements could have. All the elements are shown to be sensitive to the results as was in Part 1. Methodology studied through this study and the results are expected to make a good feedback to the repository design.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.8
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• pp.465-471
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• 2015

Adsorption experiments for radionuclides such as $^3H$, $^{90}Sr$ and $^{99}Tc$ were conducted using fractured rock collected in unsaturated zone. The released radionuclide through artificial barrier from the near surface repository can be transported by the flow of rainfall or pore water through fractures in unsaturated zone and reach to groundwater flow. Therefore, it is important to investigate transport behavior (retardation) of radionuclides through fractured rock for the safety assessment and long-term performance of repository. Fractured rock samples were collected and characterized by X-ray microtomography (XMT) analysis, which can be used to develop a more robust unsaturated fracture transport model. When fracture-filling materials are exist, distribution coefficient of $^{90}Sr$ is higher than without fracture-filling materials. In this study, batch sorption distribution coefficient ($K_d$) of radionuclide was determined and used to increase our understanding of radionuclide retardtion through fracture-filling materials.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.1
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• pp.19-35
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• 2014

A parametric sensitivity to the annual exposure dose rate to the farming exposure group has been probabilistically carried out for three principal elements associated with the nuclide transport behavior in the near-field of the pyroprocessed waste repository system. Credit time for both metal and ceramic containers, annual nuclide release rete, and the degree of loss of bentonite buffer around the container are selected as the elements and investigated for important nuclides. All the elements are shown to be sensitive to the results. Methodology studied through this study and the results are expected to make a good feedback to the repository design. As a follow-up study, separated in Part 2, the A-KRS will be deterministically assessed and then compared among each other with the normal, the worst, and the best case scenarios associated with their extreme values these elements could have.