300 years is too short, but you've got the right idea. Let's do a little experiment. In the left corner we have a nuclear plant and reprocessing facility. In

300 years is too short, but you've got the right idea. Let's do a little experiment. In the left corner we have a nuclear plant and reprocessing facility. In the right corner we have a coal power plant. The reprocessing facility removes the commercially useful isotopes and sells them, removes the unused uranium and plutonium and sends it to the fuel plant and sends the rest to the landfill. The coal plant sends it's fly ash to the landfill. Round 1 (one year's operation): We have waste from each powerplant, we build identical landfills. The coal plant fills it's landfill, the nuke plant only uses a small bit of it's. Round 2: The coal plant uses another landfill, the nuke plant is fine on it's original one. Round 10,000: The coal plant is on it's 10,000th landfill, the nuke plant has finally filled it's landfill. Round 10,001: The coal plant needed yet another. The nuke plant, however, we can take out the first material as it's now down to ambient (no more radioactive than an average bit of earth) and no longer a hazard. Thus we still do not need another landfill, nor will we ever.