The heating system comprises metal heating elements that are mounted on the concrete wall of the gallery and can be energised to generate heat, as in a conventional oven. Running through the middle of the gallery is a second heating system, which serves as a back-up and can take over heat production completely, if necessary.
The heating system is fixed to the wall of the PRACLAY gallery.
Once the heating system had been installed, the gallery was backfilled with sand and completely sealed off from the main gallery. The PRACLAY gallery seal is not part of the disposal concept under investigation but is essential to ensure even distribution of heat and pressure in and around the heated area throughout the heating phase. Hundreds of cables connected to the heating system and the measuring instruments in and around the gallery pass through this seal.
Diagram of the PRACLAY gallery after the heating system was installed (red lines), the gallery backfilled with sand (yellow) and the heated section sealed with a steel cylinder (between the orange blocks). The total length of the section to be heated is 35 metres.
A research scientist checks the measuring instruments near the metal cylinder sealing the gallery.
Click here to find out about phase 3 of the PRACLAY experiment.