Uses and Dangers of Radiation
Uses of Radioactive Materials
Radioactive materials have many practical uses in medicine, industry and research. The choice of which type of radiation to use depends on its penetrating power and ionising ability (P4.3l).
• Medical tracers: a patient swallows or is injected with a radioactive tracer (a gamma-emitting isotope with a short half-life, e.g. technetium-99m). Gamma rays pass through the body and are detected externally, allowing doctors to image organs and diagnose conditions such as cancer or kidney blockages.
• Radiotherapy: high doses of gamma rays or beta particles are targeted at cancerous tumours to kill the rapidly dividing cells. The beam is rotated around the patient so healthy tissue receives a lower dose while the tumour receives a concentrated dose.
• Sterilisation: gamma rays are used to sterilise medical equipment and food by killing bacteria. The food does not become radioactive.
Gamma emitters with short half-lives are used as medical tracers. Radiotherapy targets tumours with high-dose radiation. Gamma rays sterilise equipment and food without making them radioactive.
Industrial and Other Uses
• Thickness gauges: beta radiation is passed through materials like paper or aluminium foil during manufacturing. A detector on the other side measures how much gets through. If the material is too thick, the detector reading drops and the rollers adjust automatically.
• Smoke alarms: contain a small source of alpha radiation (americium-241). Alpha particles ionise air molecules, creating a small current. Smoke particles absorb the alpha radiation, reducing the current and triggering the alarm.
• Carbon dating: the proportion of carbon-14 (a radioactive isotope) in dead organic material decreases over time as it decays. By measuring the remaining carbon-14, scientists can estimate how old archaeological samples are (up to about 50,000 years).
The choice of radioactive isotope for a particular use depends on three properties: the type of radiation emitted, the half-life and the toxicity. For medical tracers, a gamma emitter with a short half-life (e.g. technetium-99m, half-life 6 hours) is ideal because gamma penetrates the body, and the short half-life means the patient is not exposed to radiation for long. For industrial thickness gauges, a beta emitter with a longer half-life is preferred so the source does not need frequent replacement.
In radiotherapy for cancer treatment, the radiation must be carefully targeted to maximise damage to the tumour while minimising harm to surrounding healthy tissue. Techniques include using multiple beams from different angles that converge on the tumour, so healthy tissue receives a low dose from each beam while the tumour receives a high combined dose.
Nuclear power stations use controlled nuclear fission (the splitting of heavy nuclei like uranium-235) to generate electricity. The process produces large amounts of energy from small amounts of fuel with no CO\(_2\) emissions during generation. However, it creates radioactive waste of varying levels of danger, and the risk of accidents (though rare) has significant consequences.
When selecting a radioactive source for any application, scientists weigh up the benefits (medical diagnosis, energy generation, industrial efficiency) against the risks (radiation exposure, contamination, waste disposal). This risk-benefit analysis is central to responsible use of radioactive materials. For OCR Gateway, you should be able to evaluate the benefits and risks of using radiation in given scenarios and justify whether the use is appropriate.
It is essential to distinguish between contamination and irradiation (P4.3m):
Contamination means a radioactive material is deposited on or inside the body. This is dangerous because the source continues to emit radiation in close contact with tissues. Contamination is removed by washing or decontamination procedures.
Irradiation means being exposed to radiation from an external source. The person does not become radioactive. The risk depends on the type and duration of exposure. Once the source is removed, the irradiation stops.
Contamination is generally considered more dangerous than irradiation because the radioactive material remains in contact with the body, giving continuous exposure that cannot be stopped simply by moving away.
Contamination = radioactive material on/in the body (ongoing risk). Irradiation = exposure to external radiation (stops when source is removed). Contamination is more dangerous because it provides continuous exposure.
Workers handling radioactive materials follow strict safety procedures:
• Minimise exposure time — spend as little time near sources as possible.
• Maximise distance — radiation intensity decreases with the square of the distance from the source.
• Use shielding — lead-lined containers, concrete walls and lead aprons absorb radiation.
• Wear protective equipment — gloves and lab coats prevent contamination.
• Monitor exposure — workers wear film badges or dosimeters that record their cumulative radiation dose.
• Use tongs — never handle radioactive sources directly; use long-handled tongs to increase distance.
Radioactive waste is classified by its activity and half-life. High-level waste (from nuclear reactors) must be stored securely for thousands of years, often in deep geological storage facilities. Low-level waste (contaminated clothing, gloves) is compacted and stored in shallow landfill sites.
Safety measures: minimise time, maximise distance, use shielding, wear protective equipment, monitor exposure with dosimeters, use tongs. High-level waste needs long-term secure storage.