Which process produces the energy in modern nuclear reactors

• A. Fusion
• B. Alpha decay
• C. Electron capture
• D. Fission

Answer: (D)

The energy in modern nuclear reactors comes from fission, the splitting of a heavy nucleus into lighter parts when it absorbs a neutron. When the nucleus splits, a small amount of mass disappears and is released as energy, mostly as the kinetic energy of the fission fragments and some gamma radiation. This energy heats the reactor coolant, which then turns water into steam to drive turbines. Crucially, fission can produce additional neutrons that go on to cause more fissions, creating a controllable chain reaction that sustains power. Fusion, while powerful, requires conditions not used in typical reactors and is not the method employed in present-day plants. Alpha decay and electron capture release energy too, but they occur as separate, spontaneous decays and don’t provide the sustained, controllable energy production that fission does.