I feel like you should change the data region around. It is difficult to read headings and values when it is all stored in a text box.
It would be better if that part was a little bit more like the old one with headings that have their own spot in the GUI.
You should also add stats like max temp, melting temp, etc.
If you are feeling really ambitious, add a liquid coolant feature for the 5x5 reactor design. Though this probably isn't necessary because who doesn't keep the reactor's coolant full all the time.
Also, thanks so much for this! I was almost thinking of doing this but I have little experience in Java so that stopped me.