Some nuclear reactors release beta particles because certain unstable atomic nuclei produced during the fission process undergo beta decay to reach a more stable state. Beta particles are high-energy electrons or positrons emitted when a neutron in the nucleus transforms into a proton (beta minus decay) or a proton transforms into a neutron (beta plus decay). This transformation changes the identity of the atom slightly but helps the nucleus move toward stability.
Inside a nuclear reactor, heavy elements like uranium-235 or plutonium-239 split into smaller fragments called fission products when struck by neutrons. These fission products are often neutron-rich and unstable, meaning they have more neutrons than protons compared to stable nuclei. To become stable, many of these neutron-rich fragments undergo beta minus decay, where a neutron changes into a proton, emitting an electron (the beta particle) and an antineutrino. This process increases the atomic number by one but leaves the mass number unchanged. For example, a neutron in a fission fragment can convert to a proton, releasing a beta particle as part of the decay chain toward a stable isotope.
The emission of beta particles is a natural consequence of the nuclear instability of these fission products. Since the reactor continuously produces these unstable isotopes, beta decay and thus beta particle emission occur continuously during reactor operation. Some well-known beta-emitting fission products include isotopes like technetium-99, which has a long half-life and emits beta particles as it decays toward stability.
Beta particles are relatively small and fast electrons or positrons, and they can penetrate materials more deeply than alpha particles but are generally stopped by a few millimeters of metal or plastic. In reactors, beta radiation is part of the radioactive emissions that must be carefully shielded to protect workers and the environment.
Additionally, some beta decays in fission products can lead to the emission of delayed neutrons, which are important for controlling the nuclear chain reaction in reactors. These delayed neutrons come from beta decay of certain precursors that emit a neutron shortly after the beta decay, helping to regulate the reactor’s power output safely.
In summary, nuclear reactors release beta particles because the fission process creates many neutron-rich, unstable nuclei that undergo beta decay to become more stable. This decay emits beta particles as electrons or positrons, which are a natural form of radioactive emission from the fission products continuously generated inside the reactor.
