The second episode with everyone's favourite (two people max) Retarded, Microprocessor and Train-loving Autist, Sasha.
This time I get to talk about a Nuclear Steam Locomotive. (At least I think it is). You can read about it here on the Fallout wiki. Based on the notes from that article, I think Nuclear-powered Steam Engine (Fusion heats water into compressed steam, steam drives pistons which turn wheels) is likely.