Mid life servicing for a nuke boat (sub or carrier) is traditionally cutting out and replacing the reactor. (I am not a nuke engineer so dont flame me for details). What this article implies is a reactor fuel core that lasts twice as long as its predecessors. That seems like a significant tech leap, and I suppose its possible. Maybe we just dont hear about this since nuke electrical power plant construction in the US has been so taboo for the last 50 years.
It’s my understanding that a nuclear sub might contain three such reactors in order to build in war time survivability. this implies that each reactor might fit into a train engine. Just think how rail transportation might change with autonomist driving and no refueling for fifty years.