Question

does nuclear fusion and fission wants oxygen to fusioes and fissioes

Answer 1

NO , When a single free neutron strikes the nucleus of an atom of radioactive material like uranium or plutonium, it knocks two or three more neutrons free. Energy is released when those neutrons split off from the nucleus, and the newly released neutrons strike other uranium or plutonium nuclei, splitting them in the same way, releasing more energy and more neutrons. This chain reaction spreads almost instantaneously.

Answer 2

No it does not need oxygen.