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.
“It’s my understanding that a nuclear sub might contain three such reactors in order to build in war time survivability”
Never heard of a nuclear sub with more than one reactor. Where did you get that “understanding”?