Using Radioactive Materials Safely
Contamination and Irradiation
It is essential to distinguish between two ways a person can be exposed to radiation:
Contamination — a radioactive material is deposited on or inside the body. The person effectively carries a radiation source with them; the exposure is continuous and cannot be stopped simply by moving away. Contamination is removed by washing or specialist decontamination procedures. Even weakly penetrating radiation such as alpha particles becomes highly dangerous when the source is inside the body, because it ionises tissue directly.
Irradiation — the person is exposed to radiation from an external source but does not take the radioactive material into their body. They do not become radioactive. The exposure stops as soon as they move away from the source. The risk from irradiation depends on the type of radiation, the dose received and the duration of exposure.
Contamination = radioactive material inside or on the body — ongoing risk. Irradiation = external exposure — stops when the source is removed. Contamination is generally considered more dangerous because it provides continuous exposure.
Medical Uses of Radioactive Materials
Radioactive materials have several well-established medical uses. The choice of isotope depends on the type of radiation emitted, its half-life and its toxicity to the body:
• Medical tracers: a patient swallows or is injected with a radioactive tracer. The tracer uses a gamma-emitting isotope with a short half-life — gamma rays penetrate the body and are detected externally by a scanner. This lets doctors diagnose conditions such as cancer, blocked arteries or kidney problems without surgery. The short half-life ensures the patient's radiation exposure is minimised once the procedure is complete.
• PET scans: positron emission tomography uses a short-lived radioactive tracer that emits positrons (\(\beta^+\) particles). These annihilate with electrons in the body, producing pairs of gamma rays that are detected simultaneously. PET scans are used to detect metabolically active tumours and to image brain activity.
• Radiotherapy: high doses of gamma rays or beta particles are targeted at tumours to kill the rapidly dividing cancer cells. Multiple beams from different angles converge on the tumour, so healthy tissue receives a lower dose from each individual beam while the tumour receives the full combined dose.
For a medical tracer, a gamma emitter is used because gamma rays can penetrate the body and be detected externally — alpha or beta particles would not reach the detector. A short half-life (typically a few hours) is preferred: long enough to complete the scan, short enough to minimise the patient's total radiation dose. Once imaging is complete, the activity drops rapidly.
For industrial thickness gauging (such as controlling the thickness of metal sheets or paper during manufacture), beta emitters with longer half-lives are used. The source needs to last for months or years in service without requiring frequent replacement. Too little radiation passes through if the material is too thick; too much if it is too thin — automated systems adjust rollers accordingly.
For cancer radiotherapy, high-energy gamma sources or carefully aimed beams of radiation are used. The treatment must be planned precisely using imaging data so that the radiation dose to healthy tissue is minimised while the tumour receives a lethal dose.
Risk–Benefit Reasoning (IaS4)
Decisions about using radioactive materials always involve weighing evidence about benefits against evidence about risks. This kind of reasoning — considering both sides under uncertainty — is central to how science informs public policy. A PET scan carries a small but real radiation dose; it is justified when the benefit (detecting a life-threatening tumour) outweighs the risk. But the same dose from an unnecessary scan would not be justified.
Nuclear power stations generate electricity without producing carbon dioxide during operation, which is a significant benefit in the context of climate change. The risks include the possibility of accidents (though serious accidents are rare), the generation of long-lived radioactive waste, and the security concerns around nuclear materials. Societies make decisions about nuclear power by weighing these factors — there is no purely 'scientific' answer because the weighting of values (environmental, economic, security) is a matter of policy, not just evidence.
Radioactive waste is classified according to its activity and how long it remains dangerous:
• High-level waste — the most radioactive, typically spent fuel rods from nuclear reactors. Generates significant heat from ongoing decay. Must be stored securely for very long periods — thousands of years — because the isotopes involved have long half-lives. Current approaches include vitrification (encasing in glass) and storage in deep geological repositories.
• Low-level waste — items such as contaminated protective clothing, gloves and tools used in hospitals and nuclear facilities. Activity is relatively low and can be safely compacted and stored in near-surface disposal facilities.
The challenge of long-term storage is significant: no human institution has yet existed for the thousands of years that high-level waste remains dangerous. This is one of the key ethical arguments raised by those who oppose nuclear energy expansion.
Safety Precautions
Workers who handle radioactive sources follow strict precautions to minimise their radiation dose:
• Minimise time — spend as little time near the source as possible.
• Maximise distance — radiation intensity decreases rapidly with distance from the source.
• Use shielding — lead-lined containers, lead aprons and concrete walls absorb radiation.
• Use tongs — never handle sources directly; long tongs increase distance and prevent contamination.
• Monitor exposure — workers wear film badges or dosimeters that record their cumulative radiation dose so that legal dose limits are not exceeded.
• Wear protective equipment — gloves and lab coats prevent radioactive material contaminating the skin.
All uses of radioactive materials require risk–benefit analysis. Benefits include medical diagnosis, cancer treatment and low-carbon electricity. Risks include radiation exposure, contamination and long-lived radioactive waste requiring secure storage for very long time periods.