The whole idea of having to store the spent fuel rods for 100,000 years is based on conflating the concepts of "long-term radioactive" and "highly radioactive." With the obvious exception of Uranium, the two concepts are inversely proportional: the longer the half-life, the lower the radiation and the more radioactive it is, the shorter the half-life. The isotopes that remain radioactive that long aren't very dangerous because they break down very slowly, and the ones that are the most radioactive don't last very long. And, of course, Uranium is an exception because it goes through several different reactions before becoming stable and non-radioactive so that even though it breaks down slowly, each breakdown results in a cascade of radiation.