Aha, I get it. And I like that its kinda nerdy. I dont think majority of the people will get it though. Just Plutonium would be fine, sounds actually real good and I think searching for plutonium os should be distinct enough (given the fact plutonium is not an element of everyday life). However if you still insist on the shorthand, what I saw people do, have a paragraph explaining what the shortcut means and how to call the os. Something like "the p-239 stands for plutonium and that is what we call the os - Plutonium" or variant of that. Maybe have it on the homepage even as a part of some baner or simly as second or third element under header. And it can also link to the full story (that it was a codename at first..)

my intention was for this to be the short version of Plutonium-239 so it matches better with the logo. I kind of hope for this to be colloquially refered to as just Plutonium

My first thought when I saw your domain was not plutonium-239, it was P U 239, your website doesn’t reference plutonium until 8-9 paragraphs in.

English speakers will think your distro stinks based on that name.

Hard to google though...

Might I suggest Hesperium (earlier alternate name recommended by Fermi) or Plutium (a name Seaborg considered before deciding plutonium sounded better)?