re: 30 million tonnes of radioactive waste
1 cubic foot of steel weighs around 500 lbs. If I were to convert all the 30 million tons (I'm using 2,000 lb. U.S. tons) of waste into blocks of metal a foot on a side, and place them individually three feet apart on the ground, 30 million tons would occupy a space less than seven miles on a side. The space would be a lot smaller if you piled it a little higher. Unlike fissionables, putting metal isotopes in a pile isn't going to change its radioactivity.
This is a non-problem.