Becquerel (Bq) meaning

In radiation protection, environmental permitting and nuclear law, the becquerel (Bq) expresses the activity of a radioactive substance: one nuclear disintegration per second. It is the SI unit used in regulation and compliance across the UK and Ireland, referenced in the Ionising Radiations Regulations 2017 (Great Britain), the Ionising Radiations Regulations (Northern Ireland) 2017, and Ireland’s S.I. No. 30/2019. Activity limits commonly appear in permits, licence conditions, discharge authorisations and waste clearance/exemption thresholds (often in Bq or Bq per gram), and in radon measurements (Bq/m3). 37 billion (3.7 x 10^10) becquerels = 1 curie (Ci). For comparison, the sievert (Sv) measures radiation dose/effect and is used for worker and public dose limits; the rem is a legacy non‑SI unit (1 Sv = 100 rem). Practitioners should distinguish activity (Bq) from dose (Sv) when drafting, negotiating or auditing compliance documents, conducting due diligence, classifying radioactive waste, or preparing transport documentation. Named after Henri Becquerel, co‑recipient of the 1903 Nobel prize in Physics with Pierre and Marie Curie for work on radioactivity. Usage and meaning are broadly consistent across England & Wales, Scotland, Northern Ireland and Ireland.