Nuclear Physics - Safety precautions in radioactivity

Minimizing exposure time: The total dose of radiation received is directly proportional to the time spent near the radioactive source. Reducing time reduces the biological risk.

Maximizing distance: Increasing the distance from a radioactive source significantly reduces the intensity of radiation reaching the body, following the Inverse Square Law ($I \propto \frac{1}{d^2}$). Hands should never touch a source; long-handled tongs must be used.

Shielding: Placing materials between the source and the person to absorb radiation. $\alpha$-particles can be stopped by paper, $\beta$-particles by a few millimeters of aluminum, and $\gamma$-rays require thick lead or concrete.

Storage and Labeling: Radioactive sources must be stored in lead-lined containers when not in use. These containers must be clearly labeled with the standard 'Trefoil' ionizing radiation hazard symbol.

Monitoring and Personal Protection: Workers use film badges (dosimeters) containing photographic film that darkens upon exposure. This allows for the tracking of the cumulative dose received, measured in Sieverts ($Sv$) or millisieverts ($mSv$).

Contamination vs. Irradiation: Irradiation is the process of exposing an object to radiation (it does not make the object radioactive). Contamination occurs when radioactive atoms get onto or into an object (e.g., ingestion of $\alpha$-emitters is extremely dangerous due to high ionization).

Background Radiation: Safety calculations must often account for background radiation, which comes from natural sources (radon gas, cosmic rays, rocks) and artificial sources (medical X-rays, nuclear fallout).