Afaik what makes fusion hard is maintaining the conditions that allow fusion to occur. Because of this, it’s quite safe - if anything goes wrong, it’ll just stop working.

Safe? Really?

I expect that the containment vessels will get very radioactive.

But all a bit hypothetical, since none exist

Yes they do exist, link elsewhere in this thread, Helion have a 7th generation nuclear fusion reactor fusing once every ten seconds or so. https://www.youtube.com/watch?v=_bDXXWQxK38

(It's not surplus of power, but it is repeatable fusion actually happening).

That is not a fusion reactor

We already have fission powered ships and submarines.

We almost had fission powered airplanes and airships: https://en.wikipedia.org/wiki/Nuclear-powered_aircraft

and https://en.wikipedia.org/wiki/Lockheed_CL-1201

And dreams of fission trains: https://twsmedia.co.uk/2020/05/09/atomic-trains/

Sense prevailed, and we do not have civilian mobile nuclear reactors.

The military are mad. Mad and bad. It is in the job description.

We would all be better off if none of them (the military) existed