[wildylion]

Might be. If the reactor was recently defueled, especially, might there be more junk floating in the water?

If said junk was alpha- or beta-emitting, it could be enough of a danger for cancer.

[loa_in_]

It almost sounds plausible but it's not. All fuel is extremely heavy elements that in still water falls down and deposits on the bottom.

[fsh]

The fuel is (almost) harmless, it's the fission products that make reactors dangerous. Many of those are water-soluble. Of course the fuel elements should be encased, but drinking pool water is probably not a great idea anyway.