Out of interest Dani, is it possible to use a relatively benign lithium salt solution rather than pure lithium to do the tritium recovery?<p>As for the geothermal alternative, unfortunately it seems drilling holes to geothermal depths isn't easy or cheap either. Geodynamics in South Australia are arguably at the most advanced stage and they've had multiple drilling failures at their hot fractured rock geothermal pilot plant. They originally claimed that hot fractured rock geothermal drilling was in the regular 3-5km oil and gas depth "window" and thus should be straight forward. Ubiquitous geothermal from the mantle is much deeper still, so I suspect as a viable alternative to fusion you'd just be replacing one multi-billion dollar engineering challenge with another!