Introduction to the Uses and Dangers of Ionising Radiation
In our previous lessons, we learned that radioactive isotopes emit radiation (alpha, beta, and gamma). Because this radiation is "ionising," it can be dangerous. However, if we understand how it behaves, we can harness its power to save lives in hospitals and solve problems in industry. This chapter explores how we use radiation safely and why we must be careful when handling it.
Note: If you need a refresher on what alpha \( (\alpha) \), beta \( (\beta) \), and gamma \( (\gamma) \) actually are, check back on the chapter "Types of radiation and detection."
Uses of Radiation in Medicine
Radiation is a vital tool for doctors. It is used in three main ways:
1. Medical Tracers
A patient can swallow or be injected with a radioactive isotope (a tracer). As the isotope moves through the body, a detector outside the body (like a gamma camera) tracks where it goes. This helps doctors see if organs like the kidneys or thyroid are working correctly.
Why it works: We usually use gamma radiation because it is highly penetrating and can pass out of the body to the detector without being stopped by tissue.
2. Sterilising Equipment
Medical tools like scalpels and syringes must be completely free of bacteria. Instead of using heat (which can melt plastic), manufacturers use high doses of gamma rays to kill all bacteria and viruses on the equipment after it has been sealed in its packaging.
3. Treating Cancer (Radiotherapy)
High doses of ionising radiation can kill living cells. While this sounds scary, doctors use tightly focused beams of gamma rays to kill cancer cells and shrink tumours. This must be done very precisely to avoid damaging too many healthy cells.
Uses of Radiation in Industry
Outside of hospitals, radiation helps keep factories running smoothly.
1. Thickness Gauges
In factories making paper, plastic, or metal foil, a radioactive source is placed on one side of the material and a detector on the other. If the material gets too thick, it absorbs more radiation, and the detector reading drops. A computer then adjusts the rollers to make the material thinner again.
Key Point: Beta radiation is used here. Alpha would be stopped by the paper entirely, and gamma would pass through everything regardless of thickness!
2. Finding Leaks in Pipes
To find a leak in an underground water pipe, a gamma tracer is added to the liquid. A worker moves a Geiger-Muller detector along the ground above the pipe. Where the detector shows a high count rate, the water is leaking into the soil.
Quick Review: Tracers and leak detection usually require isotopes with a short half-life. This ensures the substance doesn't stay radioactive in the body or the environment for a long time!
Contamination vs. Irradiation
This is a very common exam topic! Students often mix these two up, but they are very different.
Irradiation
Irradiation happens when an object is exposed to radiation from an external source. It is like standing near a fire to get warm. Once you move away from the source, the exposure stops. Crucially, irradiation does not make the object radioactive.
Contamination
Contamination happens when radioactive atoms actually get onto or into an object. It is like getting mud on your shoes. If you swallow a radioactive tracer or get radioactive dust on your skin, you are contaminated. You will remain radioactive until the source is removed or it decays away.
Analogy: Imagine a person standing near a radioactive source is like someone standing in the rain (Irradiation). If that person then picks up a radioactive rock and puts it in their pocket, they are now "wet" with radioactive material even if they move out of the rain (Contamination).
The Dangers of Ionising Radiation
Why is radiation dangerous? Because it is ionising. This means it can knock electrons off atoms, turning them into ions.
1. Cell Damage and Mutation
When radiation enters a living cell, it can ionise the DNA molecules. This can cause:
- Minor damage: The cell repairs itself.
- Mutations: The DNA is changed, which can lead to the cell dividing uncontrollably (this is how cancer starts).
- Cell death: High doses of radiation kill cells entirely, leading to radiation sickness.
2. Radioactive Waste Disposal
Used fuel rods from nuclear power stations remain radioactive for thousands of years. Finding a place to store this waste is difficult. It must be sealed in glass or concrete and buried deep underground in geologically stable areas to prevent it from leaking into the water supply.
Safety Precautions
To stay safe around radiation, scientists and doctors follow three main rules:
- Distance: Keep as far away from the source as possible (e.g., using long-handled tongs).
- Shielding: Use barriers like lead aprons or thick concrete walls to absorb the radiation.
- Time: Minimise the amount of time spent near the radioactive source.
Did you know? Workers in nuclear plants wear film badges. These contain photographic film that fogs up when exposed to radiation, telling the worker exactly how much "dose" they have received.
Key Takeaways Summary
- Medicine: Gamma is used for tracers (short half-life) and sterilising equipment.
- Industry: Beta is used for thickness monitoring; Gamma is used for pipe leaks.
- Contamination: Radioactive material is on or in you.
- Irradiation: You are exposed to radiation from the outside.
- Risks: Ionisation causes DNA mutations and cancer.
- Safety: Use shielding, increase distance, and decrease exposure time.