Comment by gus_massa

They don't eat the radioactive material and make it not radioactive.

[Assuming they use the radiation to get energy [1].] They just wait patiently until the radioactive atoms decay and emit radiation, like a gamma ray, and then absorb the gamma ray and use the energy. The half life of the radioactive material does not change.

[1] I still doubt this claim, but let's go along assuming the best case.