Radiation Safety Precautions

Ionising radiation (alpha, beta, gamma, X-rays) can damage living cells and DNA. Safety precautions follow three principles: reduce time, increase distance, use shielding.

The three principles

Time: Minimise the time spent near a radioactive source. Less time = less exposure.

Distance: Maximise the distance from the source. Radiation intensity decreases rapidly with distance (inverse square law for gamma).

Shielding: Place appropriate shielding between the source and the person.

Radiation	Shielding required
Alpha ($\alpha$)	Paper, skin, a few cm of air
Beta ($\beta$)	A few mm of aluminium
Gamma ($\gamma$)	Several cm of lead or thick concrete

Practical laboratory precautions

• Handle sources with long tongs (increases distance, reduces time holding).
• Never point a source toward people.
• Store sources in lead-lined containers when not in use.
• Keep sources away from the body; never eat, drink or smoke near sources.
• Monitor exposure using a film badge or dosimeter.
• Use the weakest source and shortest exposure time that will give reliable results.

Medical precautions

• X-ray technicians leave the room during imaging.
• Lead aprons protect parts of the body not being imaged.
• In radiotherapy, the beam is carefully aimed to minimise exposure to healthy tissue.

Common errors and how to correct them

• Thinking all radioactive sources are extremely dangerous. Many sources used in schools emit very little radiation and the risk, with proper handling, is very low.
• Confusing irradiation (being exposed to radiation from a source) with contamination (having radioactive material on or in the body). Irradiation stops when the source is removed; contamination requires decontamination.

How to apply this in an exam

State the three principles (time, distance, shielding). Give specific practical measures relevant to the scenario. Explain irradiation vs contamination if asked.