• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.3
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• pp.207-213
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• 2010

The effect of temperature on swelling pressure was observed with a Korean domestic Ca-bentonite which has been considered as a potential buffer material in the engineering barrier of a high level radioactive waste (HLW) disposal system. The Ca-bentonite was compacted to a dry density of 1.6 g/$cm^3$, and then de-ionized water was supplied into it with a constant pressure of 0.69 MPa. The equilibrium swelling pressures were measured with different temperatures of $25^{\circ}C$, $30^{\circ}C$, $40^{\circ}C$, $50^{\circ}C$, $60^{\circ}C$, $70^{\circ}C$, respectively. The Ca-bentonite showed a sufficiently high swelling pressure of 5.3 MPa at room temperatures. Then it was clearly showed that the equilibrium swelling pressure was decreased with an increase of temperature. Interestingly, there were some differences in temperature effect on the equilibrium swelling pressure when the environmental temperature is increasing or decreasing. For further clarifying the swelling behaviour of a Korea domestic Ca-bentonite, the change of a compaction level, and the composition variation of a supplied water would be needed to use in conceptual design of HLW disposal system.

• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.29-40
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• 2024

This study aimed to evaluate the swelling behavior characteristics of KJ-II buffer blocks by performing numerical analysis of swelling pressure measurement experiments using the nonlinear elasticity model of COMSOL Multiphysics. The analysis was conducted under boundary conditions that included isotropic constraints and water injection pressure, mirroring the experimental settings. Validation of the numerical model was achieved by comparing its outputs with experimental results. The validated model was then used to simulate swelling deformations under unconfined conditions and to analyze swelling pressure as influenced by dry density and the geometric shape of the buffer material. The results accurately represented the swelling deformation observed during the saturation process and demonstrated that swelling pressure increases with higher dry density. Moreover, simulations concerning the geometric shape of the buffer material indicated a markedly faster rate of pressure increase in U-shaped samples compared to cylindrical ones. Analysis suggested that stress manifested preemptively near the internal edges of U-shaped samples during saturation. To enhance the simulation's fidelity to actual buffer material behavior, further refinement of the analysis model using a nonlinear elasticity model is recommended.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2016.10a
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• pp.243-244
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• 2016

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2009.11a
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• pp.251-252
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• 2009

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2010.10a
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• pp.205-206
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• 2010

• Tunnel and Underground Space
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• v.29 no.6
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• pp.439-455
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• 2019

A buffer is the major component of a high level radioactive waste repository. Due to their thermal conductivity and low permeability, bentonites have been considered as a key component of a buffer system in most countries. The deep geological condition generates ground water inflow and results in swelling pressure in the buffer and backfill. Investigation of swelling pressure of bentonite buffer is an important task for the safe disposal system. The swelling pressure that can be critical is affected by mechanical and hydro properties of the system. Therefore, in this study, a sensitivity analysis was conducted to examine the effect of hydro-mechanical (HM) behaviors in the MX-80 bentonite. Based on the results of the swelling pressure generation with HM model parameters, a coupled HM analysis of an unsaturated buffer and backfill in a deep geological repository was also carried out to investigate the major factor of the swelling pressure generation.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.335-338
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• 2008

2단발포에서 금형시간이 천연고무(NR) 스폰지의 팽윤에 미치는 효과를 검토하였다. Kneader와 Rollmill을 사용하여 NR컴파운드를 제조하고 높은 압력조건의 1차금형에서 부분가교시킨 후 대기압의 2차 금형에서 발포와 가교를 완성시켰다. NR스폰지의 겉보기밀도를 측정하고 주사전자현미경을 사용하여 셀구조를 관찰하였다. 얻어진 스폰지에 대하여 실온에서 톨루엔, 이소옥탄, 항공유에 의한 팽윤거동을 조사하였다. 1차금형시간이 증가하면 NR스폰지의 겉보기밀도가 증가하고 팽윤비가 감소하였다. 2차금형시간이 증가하면 NR스폰지의 겉보기밀도가 감소하고 팽윤비가 증가하였다. 용매의 접촉에 의한 NR 스폰지의 부피팽윤비를 높이기 위하여 금형에서 동시에 발생하는 발포제의 분해반응과 NR의 가교반응을 적절히 조절하는 것이 중요하다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.4
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• pp.413-421
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• 2004

In this paper, a structural analysis for the pressurized water reactor(PWR) spent nuclear fuel disposal canister which is deposited under the 500m deep underground is carried out to predict the creep deformation of the canister while the underground water and swelling bentonite pressure are applied on the canister. Usually the creep deformation may be caused due to the Pressure and the high heat applied to the canister even though additional external loads are not applied to the canister. These creep deformations depend on the time. In this paper, oかy the underground water and bentonite swelling Pressure are considered for the creep deformation analysis of the canister, because the heat distribution inside canister due the spent fuel is not simple and depends on time. A proper creep function is adopted for the creep analysis. The creep analysis is carried out during $10^8$ seconds. The creep analysis results show that the creep strains are very small and these strains occur usually in the lid and bottom of the canister not in the cast iron insert. A much smaller strain is found in the cast iron insert. Hence, the creep deformation doesn't affect the structural safety of the canister, and also the creep stress which shows the stress relaxation phenomenon doesn't affect the structural safety of the canister.

• Tunnel and Underground Space
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• v.34 no.1
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• pp.71-87
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• 2024

In deep geological disposal of high-level radioactive waste, the surrounding rock at the immediate vicinity of the deposition hole may experience localized changes in permeability due to in-situ stress at depth, swelling pressure from resaturated bentonite buffer, and the heat generated from the decay of radioactive isotopes. In this study, experimental data on changes in permeability of granite, a promising candidate rock type in South Korea, were obtained by applying various confining pressures and temperature conditions expected in the actual disposal environment. By conducting the permeability test on KURT granite specimens under three or more hydrostatic pressure conditions, the relation in which the permeability decreases exponentially as the confining pressure increases was derived. The temperature-induced changes in permeability were found to be negligible at temperatures below the expected maximum of 90℃. In addition, by establishing a relation in which the initial permeability is proportional to the power of the initial porosity, it was possible to estimate permeability value for granite with a specific porosity under a certain confining pressure.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.515-523
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• 2001

In this paper results of a linear structural analysis for design and dimensioning of disposal containers for spent pressurized water reactor nuclear fuel and spent Canadian deuterium and uranium reactor nuclear fuel are presented. The container structure studied here is a solid structure with a cast insert and a corrosion resistant outer shell, which is designed for the spent nuclear fuel disposal in a deep repository. An evenly distributed load of hydrostatic pressure from the groundwater and large swelling pressure from the bentonite buffer are applied on the container. Hence, the container must be designed to endure these large pressure loads. In this study, the array type of inner baskets and thicknesses of outer shell and lid/bottom are attempted to be determined through a linear static structural analysis.