Jeremy Harker of Waimate High School asks :-

Nuclear fission reactions produce nuclear waste but nuclear fusion reactions dont. Is it possible to do a nuclear fusion reaction with the waste products of a fission reaction and thus eliminate nuclear waste?

Al Ghiorso, who smashes heavy atoms together with large accelerators at Berkeley in California, and who discovered element 104 and named it Rutherfordium after Ernest Rutherford, responded.

In fission the nucleus of a heavy atom such as uranium is split into two lighter nuclei with a release of energy. In fusion two light atoms such as hydrogen are pushed together to form one heavier nucleus, again with the release of energy. Fission reactors have been in commercial use since the 1950's. Fusion holds great promise but because of the difficulty of pushing two nuclei close together, power production has not yet been achieved other than in the unusual environment of a hydrogen bomb which uses a fission bomb as a detonator. Special high powered lasers are being developed to hopefully produce fusion power reactors.

Fission reactions leave behind highly radioactive nuclei, some of which have lifetimes of thousands of years. Can nuclear reactions be performed to convert these into non-radioactive nuclei? In general one cannot put the pieces back together again.

If one bombards the waste fission products with nuclei from an accelerator or a neutron reactor, in principle one can convert them into atoms that are more stable and thus more long lived. They would be 'burned' into other nearby elements with the end result being less radioactivity. At least that is the theory but there is a real question as to whether this could be cost effective. I doubt it. There was a Los Alamos project aimed at seeing whether the idea was feasible. It was pursued for a while about a decade ago.