한국 심부 지하수 환경에서의 방사성 핵종(우라늄, 플루토늄, 팔라듐) 의 지화학적 거동 모델링

Translated title of the contribution: Geochemical Modeling on Behaviors of Radionuclides (U, Pu, Pd) in Deep Groundwater Environments of South Korea

Jaehoon Choi, Sun Ju Park, Hyunsoo Seo, Hyun Tai Ahn, Jeong Hwan Lee, Junghoon Park, Seong Taek Yun

Research output: Contribution to journalArticlepeer-review

Abstract

The safe disposal of high-level radioactive waste requires accurate predictions of the long-term geochemical behavior of radionuclides. To achieve this, the present study was conducted to model geochemical behaviors of uranium (U), plutonium (Pu), and palladium (Pd) under different hydrogeochemical conditions that represent deep groundwater in Korea. Geochemical modeling was performed for five types of South Korean deep groundwater environment: high-TDS saline groundwater (G1), low-pH CO2-rich groundwater (G2), high-pH alkaline groundwater (G3), sulfate-rich groundwater (G4), and dilute (fresh) groundwater (G5). Under the pH and Eh (redox potential) ranges of 3 to 12 and ±0.2 V, respectively, the solubility and speciation of U, Pu, and Pd in deep groundwater were predicted. The result reveals that U(IV) exhibits high solubility within the neutral to alkaline pH range, even in reducing environment with Eh down to -0.2 V. Such high solubility of U is primarily attributed to the formation of Ca-U-CO3 complexes, which is important in both G2 located along fault zones and G3 occurring in granitic bedrocks. On the other hand, the solubility of Pu is found to be highly dependent on pH, with the lowest solubility in neutral to alkaline conditions. The predominant species are Pu(IV) and Pu(III) and their removal is predicted to occur by sorption. Considering the migration by colloids, however, the role of colloid formation and migration are expected to promote the Pu mobility, especially in deep groundwater of G3 and G5 which have low ionic strengths. Palladium (Pd) exhibits the low solubility due to the precipitation as sulfides in reducing conditions. In oxidizing condition, anionic complexes such as Pd(OH)3-, PdCl3(OH)2-, PdCl42-, and Pd(CO3)22- would be removed by sorption onto metal (hydro)oxides. This study will improve the understanding of the fate and transport of radionuclides in deep groundwater conditions of South Korea and therefore contributes to develop strategies for safe high-level radioactive waste disposal.

Translated title of the contributionGeochemical Modeling on Behaviors of Radionuclides (U, Pu, Pd) in Deep Groundwater Environments of South Korea
Original languageKorean
Pages (from-to)847-870
Number of pages24
JournalEconomic and Environmental Geology
Volume56
Issue number6
DOIs
Publication statusPublished - 2023 Dec

Bibliographical note

Publisher Copyright:
© 2023 Korean Society of Economic and Environmental Geology. All rights reserved.

ASJC Scopus subject areas

  • Environmental Science (miscellaneous)
  • Geology
  • Economic Geology

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