what is the fission of uranium 235
The fission of U-235 in reactors is triggered by the absorption of a low energy neutron, often termed a slow neutron or a thermal neutron. Other fissionable isotopes which can be induced to fission by slow neutrons are plutonium-239, uranium-233, and thorium-232.lutonium-239 is also fissionable by bombardment with slow neutrons, and both it and uranium-235 have been used to make nuclear fission bombs. Plutonium-239 can be produced by  breeding  it from uranium-238.