There are two ways to get energy out of a nuclear reaction: the clean way and the dirty way. The clean way isn't so clean but the dirty way is very, very dirty. The problem is that, while the dirty way isn't so easy, the clean way is very, very hard.
Of course we started with the easy, dirty way which is fission and that's where all that waste has come from. There are actually two kinds of fission waste: the fission products themselves and a load of long-lived heavy nuclides which you get when you leave uranium stewing in a neutron soup. The heavy ones are the worst.
Fission is not a long term solution to our energy needs and that waste will have to be dealt with eventually. Was it the mounting waste problem or the realization that our supply of U 235 would not last forever?
Whatever the reason, the race to build a working fusion reactor has been going on for some time and, for the moment, South Korea is in the lead. (But all credit to the boffins at Abingdon who did a lot of the initial development, despite the fact that a bunch of short-sighted accountants pulled the plug.
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Now fusion isn't exactly clean - nothing that produces free neutrons ever is - but light nuclides are much easier to deal with, not least because there aren't so many of them.
Another big plus is that, for the time being at least, it isn't possible to make a bomb out of them. All fusion bombs have a fission bomb inside.
It might not happen in my lifetime but I'll stick my neck out and predict a nuclear future. The solar future does have its merits but, if we ever hope to send a manned ship out across interstellar space, we'll need anti-matter. We'll need many tons of anti-matter and making it will consume a huge amount of energy. Such a starship will probably be built in orbit or, more likely, on the moon. There is no bio-fuel on the moon but it's an excellent place to build a fusion reactor. You don't even need a vacuum chamber!
