Exactly right. The goal with nuclear waste is basically to get it back down to levels similar the original ore. At that point, it isn't especially dangerous. M

Exactly right. The goal with nuclear waste is basically to get it back down to levels similar the original ore. At that point, it isn't especially dangerous. Many radioactive products are either very short lived, and will decay down to minimal levels within a few hundred years, or are very long lived, causing very low radioactivity. The problem are the elements that are in between which is mostly the other actinides. Those are the ones that would require tens of thousands of years or more to reach safe activity levels. Fast reactor designs don't have significant amounts of such elements in the waste. The waste will decay to uranium ore-ore like levels within only hundreds of years. The biggest issue is that they need relatively enriched uranium to operate at first. After they are started, they can be used as a breeder reactor that can take in natural uranium and convert it to the enriched uranium it needs to continue running.