Abstract
Deep geological disposal is the internationally-accepted solution to
permanently store nuclear waste such that it can safely decay without
negatively impacting the biosphere. Most nuclear waste-producing
countries are investigating disposal sites in granite, clay, saltstone
or volcanic tuff formations. However, in certain countries such as
Israel, the most feasible sites for building such a repository are
fractured carbonate rocks. To investigate potential radionuclide-rock
interactions under local conditions, a field-scale reactive transport
experiment was conducted. The experiment investigated transport of Re,
Ce, Sr and Cs in the presence of bentonite colloids through a 47-m flow
path through fractured chalk located in the northern Negev Desert of
Israel.
A 100-L tracer solution containing known concentrations of each metal,
the fluorescent dye uranine, and bentonite colloids was injected into an
observation well, while another well was pumped to induce a forced
gradient throughout the full 8-day duration of the experiment. After
five days of pumping, a second injection of 500 L tap water containing
sodium naphthionate, a different fluorescent dye, was injected into the
observation well to investigate the impact of changing the ionic
strength. Breakthrough curves of total and aqueous fractions of each
metal were modeled to determine the hydrological parameters of the flow
path and show the mobility of each metal under the site conditions
investigated.
Rhenium exhibited conservative behavior, attributable to its
ReO4- anionic form. Strontium was transported
primarily as an aqueous species, but SrCO3 colloids appeared
to be mobilized following the freshwater injection. Cesium migrated
entirely as an aqueous species throughout the experiment. Cerium
migrated as an intrinsic colloid precipitated with bicarbonate, and was
somewhat remobilized following the freshwater injection. Each metal's
transport properties were successfully modeled to demonstrate its
geochemical properties and mobility. This study suggests that although
careful consideration should be given to site-specific hydrologic and
geochemical conditions, fractured carbonate rocks can potentially serve
as a suitable barrier to radionuclide transport from a repository.
Original language | English |
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Title of host publication | American Geophysical Union, Fall Meeting 2019 |
State | Published - 1 Dec 2019 |
Event | American Geophysical Union (AGU) Fall Meeting 2019 - San Francisco , United States Duration: 9 Dec 2019 → 13 Dec 2019 https://www.agu.org/fall-meeting-2019 |
Conference
Conference | American Geophysical Union (AGU) Fall Meeting 2019 |
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Country/Territory | United States |
City | San Francisco |
Period | 9/12/19 → 13/12/19 |
Internet address |
Keywords
- 1805 Computational hydrology
- HYDROLOGY
- 1822 Geomechanics
- 1829 Groundwater hydrology
- 1832 Groundwater transport