Radioactivity is a naturally fascinating yet potentially dangerous phenomenon that significantly affects professionals exposed to radioactive materials. This article aims to demystify this concept and explain its importance in radiation protection at work and in occupational medicine.
Estimated reading time : 3 minutes
Radioactivity manifests through the spontaneous emission of radiation following the disintegration or de-excitation of an unstable atomic nucleus. Understanding these phenomena is crucial to ensure the safety of workers exposed to radiation. Radioactive sources are categorized into two groups: sealed, which contain radioactive materials, and unsealed, which do not. “Orphan” sources escape all regulation and pose a particular danger.
Measuring radioactivity: activity and half-life
The activity of a radioactive source is measured in becquerels (Bq), with one Bq corresponding to one disintegration per second. In nuclear medicine, the milliCurie (mCi) is sometimes used, where 1 mCi is equivalent to 3.7 x 107 Bq. To understand the persistence of a radioactive element, one refers to its half-life, the time required for half of the nuclei to disintegrate. This measurement is essential for managing worker protection in the long term.
Types of radioactive disintegration
There are several disintegration mechanisms:
- Alpha decay (α), where a helium nucleus is ejected, reducing the parent nucleus to a lighter nucleus.
- Beta minus decay (β-), involving the ejection of an electron and an antineutrino.
- Beta plus decay (β+), where a positron and a neutrino are emitted.
- Electron capture, a process without radiation emission, where an electron is absorbed by the nucleus.
- Gamma de-excitation (γ), which releases an electromagnetic wave without altering the nucleus’ composition.
- Internal conversion, where the nucleus’ excess energy is transferred to an orbiting electron. More rare phenomena, such as pair creation and the emission of neutrons or X-rays, can also occur.
Stability and instability of nuclei
Most atomic nuclei are unstable. Of about 3000 known nuclides, only 264 are stable, and stability tends to favor nuclei with an even number of protons (Z) and neutrons (N). Scientists use Z-N diagrams to visualize zones of nuclear instability and the “valley of stability.”
Radioactivity is an unavoidable element of our environment, especially for those working with or near radioactive materials. Understanding its principles is essential to ensure safety and the effectiveness of radiation protection.