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Nuclear radiation is genuinely double-edged. The very property that makes it dangerous — its ability to ionise atoms and so damage living cells — is also what makes it enormously useful, from diagnosing illness and treating cancer to sterilising equipment and dating ancient remains. Using radiation safely means understanding both sides: knowing how it can harm us and how to protect against it, and knowing how to choose the right isotope for each job. This lesson, part of Topic P6 (Radioactivity) of OCR Gateway Science A, draws the crucial distinction between irradiation and contamination, surveys the main uses of radiation, sets out the hazards and the safety measures, and shows how the half-life and type of radiation determine which isotope is suitable for a given task.
By the end of this lesson you should be able to distinguish irradiation from contamination, describe the main uses of radiation, explain the hazards of radiation and the precautions taken, and choose a suitable isotope (by half-life and radiation type) for a given use.
This distinction is one of the most heavily tested ideas in the whole topic, and the two terms are easy to confuse, so it is worth getting absolutely clear.
The link to the types of radiation is important here. For irradiation from outside the body, the most dangerous radiation is the most penetrating — gamma (and beta) — because alpha is stopped by skin and clothing and never gets in. But for contamination, when the source is inside you, the most dangerous radiation is the most ionising — alpha — because it deposits all its energy in a tiny region of nearby tissue and cannot escape. This neat reversal is a favourite exam point.
Exam Tip: Irradiation = exposure to radiation from an outside source (stops when you move away; does not make you radioactive). Contamination = the radioactive material itself gets onto or into you (keeps irradiating you from close range). Outside the body gamma is most hazardous; inside the body alpha is most hazardous.
Radiation has a wide range of practical uses, each exploiting a particular type of radiation and half-life.
Medical uses:
Other uses:
Exam Tip: Match the radiation type to the job: alpha → smoke detectors (easily stopped, strongly ionising); beta → thickness gauges (partly absorbed, sensitive to thickness); gamma → tracers, radiotherapy, sterilising (penetrating, escapes the body or reaches deep tissue/microbes).
The hazard of nuclear radiation comes from its ionising ability. When radiation passes through living tissue, it ionises atoms in the cells, which can damage or kill cells or change (mutate) the DNA. A high dose can cause radiation sickness and kill cells outright; a lower dose can cause mutations that may, much later, lead to cancer.
The amount of radiation a person receives is described by their radiation dose, measured in sieverts (Sv) (or, more usually, millisieverts, mSv). The dose takes account of both the amount of radiation absorbed and how harmful that particular type of radiation is to the body. A higher dose means a greater risk of harm. Everyone receives a small dose from background radiation each year; the concern is with additional exposure on top of that.
Exam Tip: Radiation harms us because it ionises atoms in cells, which can kill cells (high dose) or mutate DNA and cause cancer (lower dose). Radiation dose is measured in sieverts and reflects both how much radiation is absorbed and how damaging it is; higher dose = higher risk.
Because there is no completely "safe" dose, the guiding rule for anyone working with radiation is to keep exposure As Low As Reasonably Achievable — the ALARA principle. In practice, exposure is reduced in three main ways:
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