What kind of nuclear reaction is seen in the following reactions? (the particle 1/0 n is a neutron)?

(i) Nuclear fusion reaction (Fusion reaction)

(ii) Nuclear fission reaction (Fission reaction)

That second reaction might be more properly labeled as spontaneous fission. Generally speaking, the word fission alone refers to induced fission. Like this:

235/92 U + 1/0n ---> products