page 3-5
Ionising radiations

Photo of train of scrap
Picture 11. A trainload of scrap arriving to be melted down and recycled.
Case study – keeping scrap clean
For some years, steelmakers have used simple detectors to weed out sources of radioactive material in scrap metal. However, these simple detectors don’t find all of the contamination. Recently, Corus researchers at the Swinden Technology Centre in Rotherham have devised an ingenious method of improving the efficiency and accuracy of the detectors. Using their knowledge of radioactivity and some clever electronics, the scientists have produced a device which, as well as reducing waste in their own plants, is being sold around the world.
Using scrap
There are two main sources of iron and steel used in steelmaking:
  • iron ore, which has to be reduced in a blast furnace
  • scrap steel that is being recycled.
Recycling scrap is much better for the environment than making steel from iron ore. This is because:
  • it is much more energy efficient
  • there is less waste metal to dispose of
  • the amount of raw material being removed from the Earth is reduced.

Photo fo scrap
Picture 12. A lump of scrap that was contaminated with a radioactive isotope. This probably came from a nuclear power plant.
Active scrap
However, in the 1970s, it was found that some of the steel produced from scrap was radioactive. This is because the scrap had been contaminated by radioactive sources, which then went into the furnace and became part of the steel. The sources might have been trace amounts of, for example, technetium, which is used in the treatment of cancer. Or they might have been larger lumps of steel that had been exposed to radiation in a power plant and become radioactive.
Wasting a batch
Once the radioactive source has been melted into a batch of steel, the whole batch has to be withdrawn. This could waste 100 tonnes of steel and inflict a huge cost (millions of pounds) to clean it up. Radioactive waste has to be disposed of safely by the National Radiological Protection Board (NRPB).

Question 3-5.

Fill in the gaps in the paragraph below. Choose the best answer in each case.

a) Steel is manufactured from and from , which is more environmentally friendly. This is because, amongst other things, it . Sometimes, trace amounts of get into the steel. We call this .

Summary                   Close
  • Scrap metal is recycled to save money and the environment
  • Some scrap metal can contain radioactive sources
  • Scrap metal is screened as it enters the plant
  • Corus have developed a more efficient way of screening the scrap