"The tanks are only expected to last for 5 years, which is ridiculously short term when dealing with radiation."

The first tanks were sealed with rubber gaskets, as that was the fastest way to build a lot of them quickly. Later tanks have welded seams, but there seems no way to retrofit the older ones or build welded ones fast enough to deal with these new issues.

Fishing in the area is....ummmm... 'suspended'.