If you're going to bring up a theory, at least be complete on your analysis.

Power generation by any means other than renewables like solar, wind, or hydroelectric requires a heat sink method.

Nuclear plants are no different in that regard. In essence they're nothing but big boilers latched to turbine generators. It really doesn't matter what the heat source is. Water is still the predominant medium for cooling and they all have cooling towers for removing heat. Obviously adding heat and evaporated water to the air has some effect on the surrounding air but to make any inference that the few nuke plants around the world are a significant contributor to weather changes is an unprovable stretch.

By the way, the conventional power plants probably outnumber the nukes 100 to 1 and not only add water vapor and heat but also carbon.

You have quite the habit of making substantial theories out of one small iota of observable evidence and ignoring all the other factors that you have no data on or probably any interest in. It's mildly entertaining but don't expect some scientist to pick up on your hunch and publish some peer-reviewed scientific journal based on it.

Art