Fig. 3.
Schematic overview of the BN experiment, consisting of a vertical borehole rigged with a downhole equipment consisting of three packed-off intervals, each lined with a cylindrical sintered stainless steel filter screen to allow contact with the surrounding clay. Each interval is connected to a stainless steel water circulation unit, equipped with a circulation pump, a flow meter and water sampling containers. In two of the intervals, an online UV spectrophotometer and pH and Eh electrodes are also installed and in the circulation of Interval 1, also a Hydrogen Equilibration Unit (HEU) is available