The neutron is essential to the production of nuclear power . In the decade after the neutron was discovered by James Chadwick in 1932 , neutrons were used to induce many different types of nuclear transmutations . With the discovery of nuclear fission in 1938 , it was quickly realized that , if a fission event produced neutrons , each of these neutrons might cause further fission events , in a cascade known as a nuclear chain reaction . These events and findings led to the first self-sustaining nuclear reactor ( Chicago Pile-1 , 1942 ) and the first nuclear weapon ( Trinity , 1945 )
Trinity
Trinity (nuclear test)
Neutron