Beta minus meaning

In legal practice concerning ionising radiation (for example, nuclear licensing, environmental permitting, transport of radioactive material and personal injury claims), beta minus (β−) describes a type of radioactive decay in which an unstable atomic nucleus emits a negatively charged beta particle (an electron) together with an antineutrino, converting a neutron into a proton and increasing the atomic number by one. It is a scientific, descriptive term rather than a defined statutory term; UK and Irish legislation typically refers to beta radiation or beta particles, with β− explained in guidance and expert evidence. Understanding β− emissions is relevant to compliance, risk assessment and evidence: it informs dose calculations, shielding and contamination controls (β− has limited penetration but can cause skin dose), waste classification and segregation, and transport classification under radiological protection regimes. Typical β− emitters include strontium‑90, phosphorus‑32 and carbon‑14, encountered in medicine, industry and research. Usage and meaning are consistent across England & Wales, Scotland, Northern Ireland and Ireland, though regulatory instruments differ. The term updates the idea of “beta decay in which an electron is emitted from an atom” by specifying emission from the nucleus.