> if you are predicting out 2.5 million years that’s important I believe the stated claim is that there is enough fuel for 100,000 years, which is about 7000x

> if you are predicting out 2.5 million years that’s important I believe the stated claim is that there is enough fuel for 100,000 years, which is about 7000x smaller than the half-life of U-235. Even then, 2.5 million years with a 700 million year half-life is absolutely negligible. It's exponential decay, not linear, so you won't even get a 1% reduction. > U238 is more plentiful It's not radioactive enough; you need to subject it to a neutron flux to get something fissile, e.g. P239 through exposure in a reactor (https://www.britannica.com/technology/uranium-processing/Conversion-to-plutonium https://www.britannica.com/technology/uranium-processing/Con...), which incidentally is what breeder reactors are designed to do. If we're talking breeder reactors, then we have several orders of magnitude more energy available to us than the above calculations.