I got a question the other day about nuclear weapons and nuclear power plants. There was some confusion about something I said on the radio (Abels Tårn) a couple of weeks ago, about nuclear power and nuclear weapons... Let me divide the question into two parts:
1) How much do you have to enrich natural uranium to make a nuclear weapon, and how much do you have to enrich to make nuclear fuel?
To make a weapon you have to enrich natural uranium, that consists of 99.25% uranium-238 and 0.72% uranium-235 (and the rest is uranium-234), to you get something like 95% uranium-235 - since this is the fissile isotope.
To make fuel you only have to enrich up to around 5% uranium-235.
In theory you could have made the 95% enriched uranium into fuel, and even though it costs money to enrich (and much more money the more you enrich), you would more or less get this money back since the higher enrichment, the longer it would last (and also, the less waste you would make - but that's another question 😉 )
2) (Which was really the question I got.) Why can't we make energy from a bomb?
First of all: you could take the fissile material from a bomb and make it into fuel - it was actually done for 20 years in the Megatons to Megawatts program, and during that time 10% of all of the electricity in the US came from nuclear power plants that were fuelled with old, Russian, nuclear war heads 🙂
Second: What I was talking about on the radio was not the normal fission bomb, but a fusion/hydrogen bomb. Actually, I was talking about wether or not we manage to make fusion here on Earth, and my point was/is that we don't (yet, but maybe in the future? 😉 ) manage to make energy from fusion the way the sun does it, but it's not correct that we don't manage to make fusion at all; since in a fusion weapon (also a type of nuclear weapon, also called a hydrogen bomb or an H bomb) we do get hydrogen to fuse. But to make the conditions right, so that the hydrogen nuclei get close enough and start to fuse, to form helium nuclei, and release energy, we have to "light it" with a "normal" fission bomb first - this is what I mean by we're putting in more energy than what we're getting out. So, we make hydrogen fuse in an explosion that we start with a nuclear fission bomb - not exactly a way to produce energy 😉
Was this any clarifying at all? Or more confusing? Please let me know, and tell me if there's something I should explain in more detail <3