Uses of Nuclear Radiation
This lesson covers the practical uses of nuclear radiation in medicine, industry and everyday life — as required by the Edexcel GCSE Physics specification (1PH0), Topic 6: Radioactivity. You need to understand why a particular type of radiation is chosen for each application, linking your answer to the radiation's penetrating power, ionising ability, and half-life.
Choosing the Right Type of Radiation
The type of radiation chosen for any application depends on its properties:
| Property | Alpha (α) | Beta (β) | Gamma (γ) |
|---|
| Ionising ability | Strong | Moderate | Weak |
| Penetrating power | Low (paper/skin) | Moderate (aluminium) | High (lead/concrete) |
| Range in air | ~5 cm | ~1 m | Effectively unlimited |
The key principle: match the radiation to the task based on what the radiation needs to pass through and what it needs to interact with.
Exam Tip: For every application, you must be able to explain WHY that specific type of radiation is used. Simply naming the type is not enough — you must link your answer to penetrating power, ionising ability and/or half-life.
Medical Uses
1. Cancer Treatment — Radiotherapy (Gamma)
Gamma rays are used to destroy cancer cells inside the body.
- A focused beam of gamma radiation is directed at a tumour from outside the body.
- The gamma rays pass through the skin and healthy tissue to reach the tumour deep inside.
- The radiation damages the DNA in cancer cells, preventing them from dividing and growing.
- The beam is often rotated around the patient so that the tumour receives a high dose from all directions, while surrounding healthy tissue receives a lower dose from each angle.
Why gamma?
- Gamma rays are highly penetrating — they can pass through the body to reach internal tumours.
- Alpha would be stopped by the skin and could not reach the tumour.
- Beta would be stopped before reaching deep tumours.
2. Medical Tracers (Gamma — e.g. Technetium-99m)
Gamma-emitting radioactive isotopes (tracers) are used to diagnose medical conditions.
- A small amount of a radioactive tracer (e.g., technetium-99m) is injected into or swallowed by the patient.
- The tracer travels through the body (e.g., through the blood or digestive system).
- A gamma camera outside the body detects the gamma rays emitted by the tracer.
- This produces an image showing how the tracer moves through the body, helping to identify problems such as blocked blood vessels, kidney function issues, or bone abnormalities.
Why technetium-99m?
- It emits gamma rays — these can pass through the body to be detected externally.
- It has a short half-life (6 hours) — it decays quickly, so the patient is not exposed to radiation for a long time.
- It is not toxic and is quickly excreted from the body.
Exam Tip: When discussing medical tracers, always mention THREE things: (1) it emits gamma rays (detectable outside the body), (2) it has a short half-life (reduces patient exposure), and (3) it is not harmful to the patient. This is a classic 6-mark question.
Industrial Uses
3. Thickness Monitoring in Manufacturing (Beta)
Beta radiation is used to monitor and control the thickness of materials during manufacturing — for example, paper or metal sheets.
How it works:
- A beta source is placed on one side of the material being produced.
- A detector is placed on the other side.
- The detector measures how much beta radiation passes through the material.
- If the material is too thick, less radiation passes through → the detector reading drops → the rollers are adjusted to make the material thinner.
- If the material is too thin, more radiation passes through → the detector reading rises → the rollers are adjusted to make the material thicker.
Why beta?
- Beta radiation is partially absorbed by paper and thin metal sheets — this means small changes in thickness produce measurable changes in the detector reading.
- Alpha would be completely stopped by even the thinnest sheet — the detector reading would always be zero, regardless of thickness.
- Gamma would pass through almost unchanged — the detector reading would barely change with thickness, making it useless for measuring.
4. Sterilising Medical Equipment (Gamma)
Gamma rays are used to sterilise medical instruments and equipment (e.g., syringes, surgical tools, bandages).
- Equipment is sealed in packaging and then exposed to a high dose of gamma radiation.
- The gamma rays kill bacteria and viruses on the equipment by damaging their DNA.
- Because gamma rays are so penetrating, they can sterilise equipment through the packaging — the packaging does not need to be opened.
Why gamma?
- Gamma is highly penetrating — it passes through packaging to reach all surfaces.
- The equipment remains sealed and sterile after treatment.
- No radioactive residue is left on the equipment (gamma is an electromagnetic wave, not a particle).
5. Smoke Detectors (Alpha)
Alpha radiation is used in some smoke detectors.
How it works:
- A small alpha source (e.g., americium-241) emits alpha particles into a small air gap between two electrodes.
- The alpha particles ionise the air molecules, creating a small electric current.
- When smoke enters the detector, the smoke particles absorb some alpha particles, reducing the ionisation.
- The current drops → the alarm triggers.
Why alpha?
- Alpha particles are strongly ionising — they ionise the air effectively to create a detectable current.
- Alpha particles have a very short range (~5 cm in air) — they do not escape the smoke detector, so they pose no risk to people in the room.
- The source has a long half-life (americium-241: ~432 years) — the detector works reliably for many years without replacement.
Other Uses
6. Checking for Leaks in Underground Pipes (Gamma or Beta)
A radioactive tracer is added to the fluid flowing through an underground pipe. A detector is moved along the surface above the pipe.
- If there is a leak, the radioactive tracer will escape into the surrounding ground.
- A higher reading on the detector at a particular point indicates the location of the leak.
Why gamma (or beta)?
- The radiation must be able to pass through the ground above the pipe to reach the surface.
- Alpha would be stopped by the ground and could not be detected.
- A short half-life is preferred so that the radioactive contamination does not persist in the environment.
Summary Table of Uses
| Application | Type Used | Why This Type? | Key Property |
|---|
| Cancer treatment (radiotherapy) | Gamma | Penetrates the body to reach tumours | High penetrating power |
| Medical tracers (e.g., Tc-99m) | Gamma | Detected outside the body; short half-life | Penetrating; short half-life |
| Thickness monitoring | Beta | Partially absorbed by thin materials | Moderate penetrating power |
| Sterilising equipment | Gamma | Passes through packaging; kills bacteria | High penetrating power |
| Smoke detectors | Alpha | Strongly ionises air; short range is safe | Strong ionising ability |
| Leak detection | Gamma/Beta | Passes through ground to surface | Penetrating power |