3. Fissioning, Heat Generation and Transfer, and Burnup
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Published:2023
Energy is liberated by an exothermic reaction in the fission process due to differences in the nuclear binding energy between the incoming (i.e., neutron and uranium) and outgoing (fission products, neutrons, etc.) products of the nuclear transmutation, when a heavy nucleus, like uranium, splits into lighter nuclei. In a nuclear reactor that uses UO2 as a fuel, the main source of energy is the radioactive nuclide 235U: 235U reacts with a neutron to generate 236U (in excited state). Then, 236U splits into lighter two (e.g., 92Kr and 141Ba) or more nuclei and also produces additional neutrons, creating a chain reaction: the newly formed neutrons react with more 235U to form 236U that undergoes fission. This process repeats itself over and over again, in a controlled manner, meaning that the number of neutrons6 in the process is kept constant to maintain a steady state power generation. The energy from fission is used to generate electricity by powering a turbine.