Uses of radioactivity, radiation hazards and safety
Radioisotopes treat cancer, improve crops, find pipe leaks and date ancient objects. Radiation can also harm cells and genes, so safety measures are essential.
Radioisotopes
Isotopes are atoms of the same element with different mass numbers. A radioisotope is a radioactive isotope of an element. Radioisotopes behave chemically like the normal element. So they can be followed inside the body, a plant or a pipe by the radiation they give out. Used in this way, they are called tracers.
Uses of radioactivity
| Field | Radioisotope or radiation | Use |
|---|---|---|
| Medicine | Cobalt-60 (radio cobalt) and gold-198 (radio gold) | Treatment of cancer (radiotherapy) |
| Medicine | Iodine-131 (radio iodine) | Diagnosis and treatment of thyroid disorders such as goitre |
| Medicine | Sodium-24 (radio sodium) | Study of blood circulation and the working of the heart |
| Medicine | Iron-59 (radio iron) | Diagnosis of anaemia |
| Medicine | Phosphorus-32 (radio phosphorus) | Treatment of some skin diseases and blood disorders |
| Medicine | Gamma rays | Sterilising syringes and surgical instruments |
| Agriculture | Phosphorus-32 | Tracing how plants take up fertiliser, to improve crop yield |
| Agriculture | Gamma rays | Killing insects and germs to preserve food; stopping potatoes and onions from sprouting; making new high-yield varieties by mutation |
| Industry | Various radioisotopes; americium-241 | Finding leaks in underground pipes; checking cracks in metal castings; measuring the thickness of sheets; americium-241 in smoke detectors |
| Industry | Uranium | Fuel in nuclear power stations |
| Archaeology | Carbon-14 | Carbon dating: finding the age of fossils, wood, bones and old paintings |
| Geology | Uranium | Finding the age of rocks and of the Earth |
How carbon dating works
All living things take in carbon, including a tiny, fixed share of radioactive carbon-14. After a plant or animal dies, no new carbon enters it. The carbon-14 already inside slowly decays at a known, steady rate. By measuring how much carbon-14 is left, scientists work out how long ago it died. The method works for objects up to tens of thousands of years old.
Radiation hazards
- Radiation ionises molecules in living cells and damages them.
- Exposure from outside causes skin burns, hair loss and sores.
- Damage to the bone marrow and blood cells can cause leukaemia (blood cancer) and other cancers.
- Radiation can damage the DNA (the genetic material) in reproductive cells, causing genetic disorders (mutations) that pass to the next generation.
- Gamma rays are the most dangerous from outside the body, because they penetrate deep. Alpha sources are dangerous if swallowed or breathed in.
Safety measures
- Store radioactive materials in thick-walled lead containers.
- Workers wear lead aprons and lead gloves, and handle sources with long tongs or by remote control.
- Workers wear a dosimeter, a small badge that records how much radiation they receive.
- Do not eat, drink or smoke where radioactive materials are handled.
- Nuclear plants have thick concrete shields, and radioactive waste is sealed and stored safely, away from people.
- Keep exposure time short and stay as far from the source as possible.
- Your textbook gives the safe limit of exposure as about 100 mR (milliroentgen) per week. The overall limit is 20 mSv (millisievert) per year, as advised by the International Commission on Radiological Protection (ICRP).
Cancer hospitals in Chennai and across India use cobalt-60 machines and other radiation therapy to treat tumours. Charcoal from the Keeladi excavation near Madurai was dated using carbon-14 to learn the age of this ancient Tamil settlement.
2 marks: “Name the radioisotopes used to treat cancer and goitre.” Cobalt-60 for cancer; iodine-131 for goitre (thyroid disorders).
4 marks: “What are the hazards of nuclear radiation? List the safety measures to be taken.” Hazards: skin burns, cell damage, leukaemia and other cancers, genetic disorders. Safety: lead containers, lead aprons and gloves, tongs and remote handling, dosimeters, no eating in labs.
4 marks: “Give two uses each of radioactivity in agriculture and archaeology.” Agriculture: P-32 to trace fertiliser uptake; gamma rays to preserve food and create new varieties. Archaeology: carbon-14 dating of fossils and wood; uranium dating of rocks.
Cobalt Combats cancer; Iodine for the thyroId; Carbon is the Calendar (age).