Hazards of nuclear radiation and safety measures
Nuclear radiation ionises living tissue, killing cells and damaging genes. We cannot control natural radiation, but we can cut man-made exposure with care, distance and shielding.
Harmful effects of nuclear radiation
- It ionises and breaks the complex molecules of living tissue, which can kill cells.
- It can cause cancer, sterility and severe skin burns, and it lowers the body's resistance to disease.
- It can damage genes, so the harm can show up in unborn children and in later generations.
- It harms plants, fish and animals, so it also affects us through the food chain.
- The damage depends on the part of the body exposed and on the energy, intensity and type of radiation.
Relative biological effectiveness (RBE) of radiations
| Radiation | RBE factor |
|---|---|
| X-rays, γ-rays and β-particles | 1 |
| Thermal (slow) neutrons | 2 to 5 |
| Fast neutrons | 10 |
| α-particles and fast heavy ions | 10 to 20 |
Why alpha particles are so harmful inside the body
Alpha particles cannot get through skin, or even paper. But if an alpha source is breathed in or swallowed, it sits right next to living cells. Its very high ionising power then does great damage in a small space. That is why α-particles have the highest RBE, 10 to 20. A higher RBE means more damage for the same absorbed energy.
Safety measures
- Avoid nuclear explosions and weapon tests.
- Make only the radioisotopes we need, and handle them with care.
- Dispose of radioactive waste carefully: seal it in steel and concrete and store it far from people and water supplies.
- Use X-rays, nuclear medicines and radiation therapy only when really needed, with well-planned doses.
- Workers keep exposure time short, stay at a distance (using long tongs), work behind lead or concrete shields, and wear badges that record their dose.
Worked example: distance as protection
A small gamma source gives a dose rate of 36 units per hour at 1 m. (a) What is the dose rate at 3 m? (b) A worker must spend 10 minutes near it. How much does his dose fall if he stands at 3 m instead of 1 m? (For a small source, dose rate ∝ 1/(distance)².)
- (a) Dose rate ∝ 1/d². Going from 1 m to 3 m divides it by 3² = 9.
- Dose rate at 3 m = 36 ÷ 9 = 4 units per hour.
- (b) 10 minutes = 1/6 hour. At 1 m the dose = 36 × 1/6 = 6 units; at 3 m it is 4 × 1/6 ≈ 0.67 units.
- So the dose falls to one ninth.
(a) 4 units per hour; (b) from 6 units to about 0.67 units, one ninth as much
In the X-ray rooms of Indian hospitals, patients wear lead aprons, and staff stand behind lead screens and wear radiation badges. Doctors also advise against unnecessary X-rays, especially during pregnancy.
3 marks: “What are the harmful effects of nuclear radiation on living beings? Suggest three safety measures.” Effects: it ionises and breaks molecules in cells, kills cells, causes cancer, sterility and skin burns, lowers resistance, and damages genes, affecting future generations. Measures: avoid nuclear tests; dispose of radioactive waste carefully; use radiation in medicine only when needed; shielding, distance and short exposure for workers.
2 marks: “Name two natural and two man-made sources of nuclear radiation.” Natural: radioactive minerals in rocks and soil; cosmic rays. Man-made: nuclear tests; nuclear reactors; radioisotopes in medicine (any two).
1 marks: “Which radiation has the highest RBE factor?” Alpha particles (10 to 20).
Time short, Distance long, Shield strong: the three rules for working near radiation.