Link?Depleted Uranium Battery
depleted uranium is ... depleted, an isotope not useful for nuclear reaction. That's why it is so cheap - it is leftover from processing (finding useful isotopes).
Many links about radioactivity-powered batteries are talking about "diamond battery" using radioactive isotopes. Technology which still powers Voyagers, launched in 1977 as mature enough technology, so no breakthrough.
The only link specific to uranium was this which says about using depleted uranium as kathode material