Another possible propulsion method: Build a giant Gauss cannon [0]. Using electricity though would add another energy transformation step reducing overall efficiency. Water steam would be directly produced off the nuclear reactors heat.

[0]: https://en.wikipedia.org/wiki/Coilgun

Found an image that visualizes the multistage concept of the cannon I image: https://en.wikipedia.org/wiki/File:Haskell_USP484011_1892_01...