Nah, that’s just the global-warming-induced warm water they like, the presence of a reactor was incidental… swarms around any sort of suction system are going to be a problem.

I can offer you a upgrade in the form of an array of radioactive spinning blades if you’d like.

(in theory you could deploy your data centres in places where nutrient levels are low, so there’s less plankton and so a much reduced risk of jellyfish swarms, but I have absolutely no faith that these cowboys would even stop to think about that for one moment)