Energy is released when the nucleus of a very heavy atom splits during fission. Energy is also liberated when two very light nucleii are made to combine into one heavier nucleus. Fission occurs spontaneously in heavy nucleii but fusion requires extreme pressure. This is why fusion reactors are much easier to create than are fusion reactors. Fission events liberate neutrons, which can induce an excited state in other nucleii, resulting in further fission events. By applying the right concentrations of materials and environment where at least one subsequent fission event will result from each initial fission event (on average), one creates a fission chain reaction. The energy released by one such event is a great many times that resulting from even the most energetic chemical event.
Fusion events liberate no particles capable of causing subsequent fusion events. This explains why there is no possibility of a FUSION chain reaction.
Energetic particles such as protons, neutrons, electrons and alpha particles (bare Hydrogen nucleii) are detected in a variety of ways and for a variety of purposes. Radiac meters are used to determine the strength of radiation and to enhance safety. Some other, more esoteric, uses include determining a material's thickness or internal composition by measuring the level of radiation that passes through a "target."
Photons, massless energy packages that include light and X-rays, are liberated during fusion, fission or through other means. X-rays, for example, are emitted when certain metals are heated.
Electrons are sucked away from red-hot metal coils in a vacuum tube amplifier. The electrons become loosely held by the metal when red-hot, and a positive charge applied to another coil or grid surrounding the red-hot cathode attracts the electrons away.
Nuclear technology is the technology of the component parts of the atom and the products resulting from the manipulation of those parts.