Thank you for taking part in the experiment.
The nuclear cannon is only made available for certain experiments and situations.
(It is impossible to get it, as the game will always end before you have the money. I guess you could get like a mouse clicker and input 999999999999 clicks per second and if you are fast enough, you will get it. But I didn't code it in, it just instantly ends the game. - I just needed a 6th item to fill up the shop because I didn't know how to center a 2 item row lol)