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.

LTD Phase 3

Radionuclide decrease in ciruclation borehole

LTD Radionuclide decrease in ciruclation borehole location

Circulation borehole

LTD 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

LTD observation borehole

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)

LTD radionuclide breakthrough

LTD simulated H3 concentration dilution

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 Diffusion - Long Term Diffusion project (LTD)