If ITER is successful then it will be the saving grace of humanity. Being able to have a limitless, emission free source of power will bring hundreds of millions out of poverty and help prevent climate change.
What humanity sized problem is Blockchain solving ? It's maybe a better payment system, maybe a better data storage approach, maybe a better contract mechanism. That's all. Not guaranteed. Just maybe.
The emissions it enables through the reckless waste of power does not outweigh the currently limited benefits.