Effect of colloids on radionuclide migration for performance assessment
of HLW disposal in Japan*
S. Kurosawa and S. Ueta
Advanced Energy and Ecosystem Department, Naka Research
Center, Central Research Institute, Mitsubishi Materials Corporation,
Ibaraki, Japan
Abstract: Colloidal effect is one of the major factors to enhance
the migration of radionuclides in groundwater. The experimental and
theoretical studies of colloid mobility and colloid-facilitated radionuclide
transport for the performance assessment of high-level radioactive waste
(HLW) geological disposal is presented in this paper. The major aims
of the study are (1) to study the filtration effect on colloids by the
engineered barrier system, (2) to study bentonite colloid generation
by erosion of the engineered barrier system, and (3) to calculate radionuclide
migration with groundwater colloids through fractured rock systems.
Alternative coagulants based on prehydrolyzed forms of aluminium or
iron can be more effective than the traditional materials in many cases,
but their mode of action is not completely understood, especially with
regard to the role of charge neutralization and hydroxide precipitation.
Basic principles of colloid stability and metal ion hydrolysis are
briefly reviewed, and the action of hydrolyzing metal coagulants is
then discussed, with some examples from recent experimental studies.
Although it is possible to interpret results reasonably well in terms
of established ideas, there are still some uncertainties that need to
be resolved
* An issue of reviews and research papers based on
presentations made at the IUPAC/ICSU Workshop on
Electrochemistry and Interfacial Chemistry in Environmental Clean-up
and Green Chemical Processes, Coimbra, Portugal, 6-7 April, 2001.
** Corresponding author.
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