There's also this:
"Design of an accelerator-driven system for the destruction of nuclear waste"
Y Kadi, JP Revol - 2003 - osti.gov
> "Progress in particle accelerator technology makes it possible to use a proton accelerator to produce energy and to destroy nuclear waste efficiently. The Energy Amplifier (EA) proposed by Carlo Rubbia and his group is a sub-critical fast neutron system driven by a proton accelerator. It is particularly attractive for destroying, through fission, transuranic elements produced by present nuclear reactors. "
Not much seems to have happened since then other than simulations, however. It might be more applicable for the minor actinides that contaminte 'spent' nuclear fuel, maybe, and which tend to have very long half-lives, but it should work for plutonium as well, though maybe MOX fuel is the better option:
https://en.wikipedia.org/wiki/Minor_actinide
> "The most important isotopes of these elements in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252."