Peterike
is it possible to somehow pass legislation that will proactively prevent these phony legal challenges?

Yes it is. The US Constitution explicitly states that the jurisdiction of the Federal Courts shall be whatever Congress says it is. If Congress wants to take away suits that are used to delay the building of nuclear power plants they can pass a law that removes such lawsuits from the jurisdiction of the Federal Courts. And insofar as State Courts are concerned, if the would-be builders of such plants have a permit from the NRC to build one, federal preemption will get those thrown out too.