Actually hundreds of millions of tonnes of fission waste
Canada alone has an inventory of 213 million tonnes of uranium tail millings, 2.29 million cubic meters of low-level radioactive waste, and 6800 cubic meters of nuclear fuel waste in storage. In 2003 we produced 0.6 million tonnes of uranium tail millings, 7300 cubic meters of low-level radioactive waste, and 250 cubic meters of nuclear fuel waste. From what I've heard, it's difficult to convert all of it to a definite amount in kilograms, but volume is known. My impression is that nuclear fusion would be preferable, of course I could be wrong.