Fungus at Chernobyl absorbs nuclear radiation via radiosynthesis
There's simply no way that this type of fungus could absorb enough radiation simply because it's not dense enough.If you want to absorb radiation you have to block it which means it has to come into contact with matter.The only way you can do this is to have either a smaller volumetric amount of something that's dense (lead, gold, uranium, etc) or a LARGE amount of something less dense (water, concrete, etc).If you're just talking about an organic organism, sure, it can use the radiation BUT you'd need to have a MASSIVE amount of it in terms of volume and weight.Simply put, the fungus itself is sparse when looking at it from a subatomic perspective. Most of the radiation passes right through it.