Uses and Hazards of Radiation

Uses and Hazards of Radiation

Radioactive materials have many beneficial applications in medicine, industry, and science. However, they also pose serious health risks. Understanding both the uses and hazards — and how risks are managed — is essential.

Hazards of Radiation

Ionising radiation (alpha, beta, gamma) can damage or destroy living cells by ionising atoms in DNA molecules. This can lead to:

• Cell death — high doses kill cells outright, causing radiation sickness (nausea, hair loss, organ failure)
• Mutations — radiation can alter DNA, which may cause cells to divide uncontrollably, leading to cancer
• Hereditary effects — mutations in reproductive cells can be passed to offspring

The level of risk depends on:

• The type of radiation (alpha is most dangerous INSIDE the body because of its high ionising power; gamma is most dangerous OUTSIDE the body because it can penetrate to reach internal organs)
• The dose received (higher dose = more damage)
• The duration of exposure
• Whether the source is inside or outside the body

Medical Uses

Diagnosis

Gamma cameras and tracers: A patient swallows or is injected with a radioactive tracer (e.g. technetium-99m). The tracer emits gamma rays that pass out of the body and are detected by a gamma camera. This produces an image showing how organs are functioning.

Requirements for a medical tracer:

• Must be a gamma emitter (gamma penetrates the body to reach the detector)
• Must have a short half-life (hours, not years) so the patient is not exposed for too long
• Must not be toxic

Technetium-99m has a half-life of 6 hours — long enough to take images, short enough to decay quickly.

PET scans use positron-emitting tracers (e.g. fluorine-18) to produce detailed 3D images, often used to detect cancers.

Treatment

Radiotherapy uses high doses of gamma rays or X-rays to destroy cancer cells. The radiation is focused on the tumour from multiple angles to maximise the dose to the tumour while minimising damage to surrounding healthy tissue. The beams rotate around the patient so that only the tumour receives the full dose at the intersection of all beams.

Iodine-131 (a beta emitter with an 8-day half-life) is used to treat thyroid cancer. The thyroid gland naturally absorbs iodine, so the radioactive iodine concentrates in the gland and the beta radiation destroys the cancerous cells locally.

Sterilisation

Gamma rays from cobalt-60 are used to sterilise medical equipment (surgical instruments, syringes) without heating or wetting them. The gamma radiation kills bacteria and viruses. The equipment does not become radioactive (this is irradiation, not contamination).

Industrial Uses

Thickness monitoring: In paper mills or metal rolling, a beta source is placed on one side of the material and a detector on the other. If the material becomes too thick, fewer beta particles reach the detector; if too thin, more get through. The machinery automatically adjusts. Beta is used because it is partially absorbed by thin materials — alpha would be stopped by anything, and gamma would pass through without significant change.

Checking for leaks: A gamma-emitting tracer is added to fluid in underground pipes. A detector above ground can locate leaks by finding where activity is unusually high.

Dating and Archaeology

Carbon dating: Living organisms absorb carbon-14 (a radioactive isotope) from the atmosphere. When they die, the carbon-14 decays with a half-life of 5,730 years and is not replaced. By measuring the proportion of carbon-14 remaining in a sample, scientists can estimate how long ago the organism died. This works for samples up to about 50,000 years old.

Rock dating: Uranium-238 decays (through a long chain) into lead-206, with a half-life of 4.5 billion years. By measuring the ratio of uranium to lead in a rock, geologists can determine the age of the rock. This method established that the Earth is approximately 4.6 billion years old.

Nuclear Power

In a nuclear power station, the nuclei of uranium-235 (or plutonium-239) undergo nuclear fission — they are split by neutrons, releasing a large amount of energy.

Each fission event:

1. A neutron is absorbed by a uranium-235 nucleus

2. The nucleus becomes unstable and splits into two smaller nuclei (fission products)

3. Two or three neutrons are released

4. A large amount of energy is released (as kinetic energy of the products)

The released neutrons can cause further fissions, creating a chain reaction. In a reactor, this is controlled using control rods (usually boron) that absorb excess neutrons to keep the reaction at a steady rate.

Advantages: No CO2 during operation, very high energy output per kg of fuel, reliable base-load power.

Disadvantages: Produces radioactive waste that remains hazardous for thousands of years, risk of accidents (though very rare), high construction and decommissioning costs.

Nuclear waste is categorised as low, intermediate, or high level. High-level waste is stored in cooled tanks and may be vitrified (sealed in glass blocks) for long-term storage deep underground.

Nuclear fusion — the joining of small nuclei (e.g. hydrogen) to form larger ones — is the process that powers stars. It releases even more energy than fission but requires extremely high temperatures and pressures. Scientists are working towards controlled fusion for power generation, but it is not yet viable.

Exam Tips

• Always match the type of radiation to the use and explain WHY that type is suitable (e.g. gamma for tracers because it penetrates the body)
• For six-mark questions on nuclear power, discuss advantages AND disadvantages, including waste disposal
• Remember: irradiation does not make objects radioactive — contamination does