Someone please correct me if I'm wrong, but isn't the problem that Uranium has a half-life of a couple hundred million years, while the half life of beryllium is less than a second?
Only Beryllium-10 has a long half-life for beta decay. Adding another neutron drops that back down to a few seconds and additional neutrons drop it back to a fraction of a second. So as long as that specific type of Beryllium isn't used, it would be fine, right?