Two questions and two suggestions:
Can you build in support for command-line arguments? Specifically it would be nice to be able to call "Java -jar Sim.jar -info somereactor.sav" or somesuch and have it not start up the GUI at all, but just print out the info and exit...
The other thing is: what is the format of your save files?
Also, for the reactor info, you could build a "fast" switch in. Basicially it would run the sim for one step, and the extrapolate from there. It would work only if the reactor doesn't have water, lava, or ice (as those are the only things where their temperature contribution is temperature-dependent), and doesn't break components during operation. Basically you'd take the maximum increase in heat of any component (including the reactor itself), and extrapolate from there.
Finally, could you color-code the background of a) the cells and b) the reactor area, toggable from more red == higher heat to red = heat excess and blue = heat deficit? That would be useful for optimising reactors...
I'm considering building a reactor brute-forcer/random reactor generator (with some simple optimisations) - I have the logic flow planned but not the actual program written, but I won't be able to unless this happens (and the sim comes out:P)