power and water, page-22

Had another look at GDY site. It seems that the primary liquid will be water at very high pressure. Having worked on design of HPAL nickel leach plants (op temp 250 C) I cant see a major problem in containing it. Corrosion control will be very important.

The secondary circuit is ammonia-water. They seem to be converting this to gas to drive the turbines. They will then need to be cooled (reliquify) to put it back in the heat eachanger.

The primary liquid may (probably will) contain radon gas and you would not want to vent this off anywhere. Much better to shove it back down into the granite.