When working on reactors i found quite disappointing that you can break a working nuclear reactor (or a just turned off one) without any problem, moreover if you break a high temperature reactor, heat and part of the fuel just disappears without consequences.
I also think that despite the lack of immersion, this is really helpful when you have to test complex designs so i don't know if that is intentional.
I love this mod and i'm sure that there are already great plans for a better implementation, so i don't want to make a long term and complex suggestion, but in my opinion there are a couple of relatively simple tweaks that can add a little more immersion.

When a player turn of the reactor, he have to wait until heat reach a safe level.
If a player try to break the reactor while running, or when heat is too high 2 things happens:

1. an aoe poison effect with power related to the residual amount of nuclear material in the reactor for radiation emission.
2. a explosion proportional to the stored heat in the reactor, and maybe, if the temperature is high enought a partial fusion.
   for a creative users that just want to test a reactor setup, poison is not a problem and maybe a creative only item that make heat instantly disappear can be added.

Thank you very much for this great mod and i'm looking forward to see how it will develop.

Oh yes, all that sort of stuff will be added when radiation is introduced - hold onto your hats!

Ok, reactors which run too hot will produce a lot more radiation as a penalty. Right now, I can't implement the 'breaking a hot reactor' effects because of the way I've implemented them, but for now the current radiation system should suffice :)