Sensitivity analysis of radionuclide migration in compacted bentonite: A mechanistic model approach

Michael Ochs, Barbara Lothenbach, Masahiro Shibata, Haruo Sato, Mikazu Yui

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13 Citations (Scopus)

Abstract

Mechanistic model calculations for the migration of Cs, Ra, Am and Pb in compacted bentonite have been carried out to evaluate sensitivities with respect to different parameter variations. A surface chemical speciation/electric double layer model is used to calculate: (i) porewater composition and radionuclide speciation in solution and at the bentonite surface, yielding the distribution of mobile and sorbed species and (ii) interaction of diffusing species with negatively charged pore walls to obtain diffusion parameters. The basic scenario considers the interaction of compacted bentonite with a fresh-type groundwater; variations include the presence of bentonite impurities and saline groundwater. It is shown that these scenarios result in significant variations of porewater composition that affect migration via three mechanisms that can partly compensate each other: (1) effects on sorption through radionuclide complexation in solution, and competition of major cations for surface sites; (2) changes in radionuclide solution speciation leading to different diffusing species under different conditions; (3) effects on diffusion through changes in the electric double layer properties of the clay pores as a function of ionic strength.

Original languageEnglish
Pages (from-to)313-328
Number of pages16
JournalJournal of Contaminant Hydrology
Volume61
Issue number1-4
DOIs
Publication statusPublished - Mar 2003
Externally publishedYes

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Keywords

  • Bentonite
  • Diffusion
  • Modeling
  • Radionuclides
  • Sorption

ASJC Scopus subject areas

  • Earth-Surface Processes

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