Long Term Diffusion (LTD) - Phase 3
LTD Phase 3: In-situ test and lab experiments
The second in-situ diffusion experiment consists of a circulation borehole (through which radionuclides are circulated in a packered-off interval), and an observation borehole ca 8 cms from the circulation borehole for sampling H-3 and Cl-36 diffusion plumes in-situ.
Radionuclide decrease in ciruclation borehole
The concentration decrease is due to diffusion and/or sorption of radionuclides into the rock matrix
Radionulicde breakthrough in observation borehole
The H-3 break-through in the observation borehole occured ca. 100 days after start of circulation
Cl-36 break-through occured approximately after 500 days from the start of ciruclation
Data points so far plot on or near concentrations predicted by advection-diffusion models (dashed line in figure below)
Models versus data – observations so far
- Initial drop in activity (H-3, Na-22, Cl-36) due to initial mixing in circulation system.
- Consistent with volumes in tank, lines and interval (dilution by ca. 10%).
- Evolution approximately as expected, with slightly faster rate of decrease after 84 days (H-3) and 40 days (Cl-36)
- Ba-133 seems to sorb much more strongly than expected.
Long Term Diffusion project (LTD) Experiment