It doesn't really eat the nuclear waste, it "just" feeds on the radioactive energi, so it doesn't speed up the decay. But you can use them as a radiation shield.
That just gives you radioactive bacteria who might crawl around a bit and spread the radioactivity. You can't get rid of a nuclear problem by chemistry.
We already have radiotrophic fungus, found near Chernobyl. Interestingly they appear to use melanin to absorb and utilise energy from the radiation.
https://en.wikipedia.org/wiki/Radiotrophic_fungus
It doesn't really eat the nuclear waste, it "just" feeds on the radioactive energi, so it doesn't speed up the decay. But you can use them as a radiation shield.
That just gives you radioactive bacteria who might crawl around a bit and spread the radioactivity. You can't get rid of a nuclear problem by chemistry.