Assessing the Geochemical Evolution of Engineered Barrier Systems Under Seawater Intrusion for High-Level Radioactive Waste Disposal Repository

Jeonghwan Hwang,Jung-Woo Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

Understanding the long-term geochemical evolution of engineered barrier system is crucial for conducting safety assessment in high-level radioactive waste disposal repository. One critical scenario to consider is the intrusion of seawater into the engineered barrier system, which may occur due to global sea level rise. Seawater is characterized by its high ionic strength and abundant dissolved cations, including Na, K, and Mg. When seawater infiltrates an engineered barrier, such dissolved cations displace interlayer cations within the montmorillonite and affect to precipitation/ dissolution of accessory minerals in bentonite buffer. These geochemical reactions change the porewater chemistry of bentonite buffer and influence the reactive transport of radionuclides when it leaked from the canister. In this study, the adaptive process-based total system performance assessment framework (APro), developed by the Korea Atomic Energy Research Institute, was utilized to simulate the geochemical evolution of engineered barrier system resulting from seawater intrusion. Here, the APro simulated the geochemical evolution in bentonite porewater and mineral composition by considering various geochemical reactions such as mineral precipitation/dissolution, temperature, redox processes, cation exchange, and surface complexation mechanisms. The simulation results showed that the seawater intrusion led to the dissolution of gypsum and partial precipitation of calcite, dolomite, and siderite within the engineered barrier system. Additionally, the composition of interlayer cation in montmorillonite was changed, with an increase in Na, K, and Mg and a decrease in Ca, because the concentrations of Na, K, and Mg in seawater were 2-10 times higher than those in the initial bentonite porewater. Further studies will evaluate the geochemical sorption and transport of leaked uranium-238 and iodine-129 by applying TDB-based sorption model.

The geochemical evolution of very dilute CO₂-rich water in Chungcheong Province, Korea: processes and pathways

KIM, K.,JEONG, D. H.,KIM, Y.,KOH, Y.-K.,KIM, S.-H.,PARK, E. Blackwell Publishing Ltd 2008 Geofluids Vol.8 No.1

<P>Abstract</P><P>A geochemical study was carried out on the CO<SUB>2</SUB>-rich water occurring in granite areas of Chungcheong Province, Korea. In this area, very dilute and acidic CO<SUB>2</SUB>-rich waters [62–242 mg l<SUP>−1</SUP> in total dissolved solid (TDS), 4.0–5.3 in pH; group I) occur together with normal CO<SUB>2</SUB>-rich waters (317–988 mg l<SUP>−1</SUP> in TDS, 5.5–6.0 in pH; group II). The concentration levels and ages of group I water are similar to those of recently recharged and low-mineralized groundwater (group III). Calculation of reaction pathways suggests that group I waters are produced by direct influx of CO<SUB>2</SUB> gas into group III type waters. When the groundwater is injected with CO<SUB>2</SUB>, it develops the capacity to accept dissolved solids and it can evolve into water with very high solute concentrations. Whether the water is open or closed to the CO<SUB>2</SUB> gases becomes less important in controlling the reaction pathway of the CO<SUB>2</SUB>-rich groundwater when the initial <I>p</I><SMALL>CO</SMALL><SUB>2</SUB> is high. Our data show that most of the solutes are dissolved in the CO<SUB>2</SUB>-rich groundwater at pH > 5 where the weathering rates of silicates are very slow or independent of pH. Thus, groundwater age is likely more important in developing high solute concentrations in the CO<SUB>2</SUB>-rich groundwaters than accelerated weathering kinetics because of acidic pH caused by high <I>p</I><SMALL>CO</SMALL><SUB>2</SUB>.</P>

Simulation of Geochemical Evolution of Bentonite Buffer Using an Adaptive Process-based Total System Performance Assessment Framework (APro)

Jeonghwan Hwang,Jung-Woo Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1

In the engineered barrier system of deep geological disposal repository, complex physicochemical phenomena occur throughout the entire disposal time, consequently impacting the safety function. The bentonite buffer, a significant component of the engineered barrier system, can be geochemically altered due to the changes in host rock groundwater, temperature, and redox condition. Such changes may have direct or indirect effects on radionuclide migration in case of canister failure. Therefore, a modeling tool that accounts for coupled thermal-hydraulic-mechanical-chemical (THMC) processes is necessary for the safety assessment. To this end, the Korea Atomic Energy Research Institute (KAERI) has developed the APro, a modeling interface for conducting safety assessment of deep geological disposal repository. The APro considers coupled THMC processes that influence radionuclide migration. Here, the solute transport considering thermal and hydraulic processes are calculated using the COMSOL multi-physics, while geochemical reactions are carried out in PHREEQC. The two software are coupled using a sequential non-iterative operator splitting approach, and transport of non-water H, non-water O, and charge were additionally considered to enhance the coupling model stability. Finally, the applicability of APro to simulate long-term geochemical evolution of bentonite was demonstrated through benchmark studies to evaluate the effects of mineral precipitation/dissolution, temperature, redox, and seawater intrusion.

천안 운전리 청동기 유적지에서 출토된 무문토기의 정량분석, 산지 및 소성조건

최석원,이찬희,오규진,이효민,이명성,Choi, Seok-Won,Lee, Chan-Hee,Oh, Kuy-Jin,Lee, Hyo-Min,Lee, Myeong-Seong 국립문화재연구원 2003 헤리티지:역사와 과학 Vol.36 No.-

The plain coarse pottery from the Unjeonri Bronze Age relic sites in the Cheonan, Korea were studied on the basis of clay mineralogy, geochemistry and archaegeological interpretations. For the research, the potteries are utilized at the analysis for 6 pieces of plain coarse potteries. Color of the these potteries are mainly light brown, partly shows the yellowish brown to reddish brown. The interior, surface and inside of the pottery appear as different colors in any cases. Original source materials making the Unjeonri potteries are used of mainly sandy clay soil with extreme coarse grained irregularly quartz and feldspar. The magnetic susceptibility of the Unjeonri pottery range from 0.20 to 1.20. And the Unjeonri soil's magnetic susceptibility agree almost with 0.20 to 1.30. In the same magnetization of soil and pottery, the results revealed that the Unjeonri soil and low material of pottery are same produced by identical source materials. The Unjeonri potteries and soil are very similar patterns with all characteristics of soil mineralogy, geochemical evolution trend. The result seems to be same relationships between the behavior and enrichment patterns on the basis of a compatible and a incompatible elements. Consequently, the Unjeonri potteries suggest that made the soil to be distributed in the circumstance of the relic sites as the raw material are high in a greater part. In the Unjeonri soil, the kaolinite is common occurred minerals. However, in the Unjeonri pottery, the kaolinite was not detected in all broken pieces. The kaolinite was presumed to destroy crystal structure during the firing processes of over $550^{\circ}C$. The quartz is phase transition from ${\alpha}$-quartz to ${\beta}$-quartz at $573^{\circ}C$, but the Unjeonri pottery did not investigated any phase transition evidences of quartz. The chorite was detected within the mostly potteries and soils. As the results, the Unjeonri potteries can be interpreted by not experiencing a firing temperature over $800^{\circ}C$. The colloidal and cementing materials between the quartz and low materials during the heating did not exist in the internal part of the potteries. An any secondary compounds by heating does not appear within the crack to happen during the dry of the pottery. The hyphae group are kept as it is with the root tissue of an organic matters to live in the swampy land. In the syntheses of all results, the general firing condition to bake and make the Unjeonri pottery is presumed from $550^{\circ}C$ to $800^{\circ}C$. However, the firing condition making the Unjeonri pottery can be different firing temperature partially in one pottery. Even, the some part of the pottery does not take a direct influence on the fire.

Provenance Presumption for Rock Properties of the Five Storied Stone Pagoda in the Jeongrimsaji Temple Site, Buyeo, Korea

이찬희(Lee C.H.),김영택(Kim Y.T.),이명성(Lee M.S.) 대한지질학회 2007 지질학회지 Vol.43 No.2