If you would like to stick to the more realistic 'nukes' that don't use elements that could be considered 'cheaty':

If you need long ambient heat (like melting the nuclear bunker save), I usually add BCLN(BIZR) too. BIZR turns into BIZS in the trajectory of the flying BCLN, and it preserves the heat of the bomb for a long time.

or i just figured out, make a circle of titanium, then delete all of the center, so it is around a 3-5 pixel thick ring, then put a small amount of polonium in it, then fill the rest with deut and set its life to 70000 and wait

THIS POST IS FROM 2017

what i did was make a large hollow circle filled 75% of it with EXOT and 25% with electrons (paused) the when you unpause it and it should react quickly heating the EXOT to the point it liquefies and it  will burn through most things

no-no-no! you will see an immensely powerful bomb. It is a specific type of bomb The AZURE WEAPON. Read the comments to see how to make it.?ID=2611804