| Title: |
DIGIT: An In Situ Experiment for Studying the Diffusion of Water and Solutes Under Thermal Gradient in the Toarcian Clayrock at the Tournemire URL; Part 2—Lessons Learned After 20 Months of Heat |
| Authors: |
Maïwenn Humbezi Desfeux; Jean-Michel Matray; Aurelie Noret; Uy Vo; Son T. Nguyen; Mamadou Fall; Julio Á. I. Sedano; Charles Wittebroodt; Manuel Marcoux |
| Source: |
Minerals ; Volume 16 ; Issue 4 ; Pages: 380 |
| Publisher Information: |
Multidisciplinary Digital Publishing Institute |
| Publication Year: |
2026 |
| Collection: |
MDPI Open Access Publishing |
| Subject Terms: |
clayrock; mass transfer; heat transfer; mobile anions; water stable isotopes; Fick’s law; thermodiffusion; Soret effect; advection |
| Subject Geographic: |
agris |
| Description: |
The DIGIT experiment was launched at the Tournemire Underground Research Laboratory (URL) with the aim of determining the effects of temperature on the transfer of tracers mimicking the most mobile radionuclides in the Toarcian clay rock. The properties of this rock are similar to those of the host rocks being considered for a future deep geological repository for high-level radioactive waste (HLW). The experiment involves the monitoring of the interaction between a test water doped with stable halides and deuterium at constant concentration, and the porewater of the Toarcian clay rock under constant ambient conditions, as well as at higher temperature induced by artificial heating. This experiment seeks to partially address questions regarding the potential spread of contaminants during the thermal phase of HL waste packages. Specifically, the in situ experiment aims to evaluate the role of scale effects, thermodiffusion, a process that combines Fick’s law, the Soret effect, and convection in the transfer of radionuclides. This paper is the second part of a companion paper dedicated to predictive calculations and the installation of the experimental device. It presents the main experimental and modeling results obtained since the beginning of the installation and after 20 months of heat at 70 °C. The test was carried out in five phases, finishing with a sampling campaign: a phase 0 called “initial conditions”, followed by a pure diffusion phase (5 months), then three phases in a heated period lasting 1 year and 8 months. In total, 47 rock cores were analyzed, with approximately 170 samples tested by four diffusion methods (radial, outgoing, through and in vapor-phase) to determine the tracer concentrations in the porewater, their water content and their diffusive transport parameters. The results show a decrease in tracer concentrations with distance from the test zone, in the directions parallel and perpendicular to the stratification. The anisotropy of the medium results in greater migration in the direction ... |
| Document Type: |
text |
| File Description: |
application/pdf |
| Language: |
English |
| Relation: |
Clays and Engineered Mineral Materials; https://dx.doi.org/10.3390/min16040380 |
| DOI: |
10.3390/min16040380 |
| Availability: |
https://doi.org/10.3390/min16040380 |
| Rights: |
https://creativecommons.org/licenses/by/4.0/ |
| Accession Number: |
edsbas.4FD1F1FB |
| Database: |
BASE |