So, this is a question that has been puzzling me for numerous reasons. Be it for advocating nuclear power, or getting a bit of nerd rage when watching a sci-fi work, or having an argument with someone.
Pretty much everyone knows that you need as much U235 you can get in a given concentration of uranium to make a bomb that's feasible and practical since the presence of U238 slows down the reaction. So working that backwards, is there a concentration of U238 to U235 where it's impossible for it to become supercritical because there are too many U238 atoms absorbing the neutrons and thus cannot trigger a nuclear detonation?
I have looked at the wiki for it: https://en.wikipedia.org/wiki/Enriched_uranium#Highly_enriched_uranium_.28HEU.29
If I am reading the second to last sentence on the first paragraph correctly, that would mean any Uranium that is below 5.4 enrichment would be physically incapable of undergoing nuclear detonation regardless of mass of uranium involved. But I'm not sure I am interpreting what they have to say correctly, so I am asking here for further clarification.
Since reactor grade uranium is only 3-4% enriched, that should mean it is impossible for that grade of uranium to ever achieve nuclear detonation, even if you tried. There is also a blurb about this notion (fact?) in this Chernobyl footage, but given it's age, and lack of explanation as to why, I'm not sure this is a valid source. https://youtu.be/Cc-vvhWXL9Q?t=14m50s
So, if I got all my duck in a row and understanding this correctly, assuming 3-4% enriched uranium is being used, would it be accurate to say that nuclear reactors (Of the above parameters), cannot, and won't ever explode in the sense of an atom bomb?