Background Radiation (Oxford AQA IGCSE Combined Science Double Award)

Background Radiation

• It is important to remember that radiation is a natural phenomenon

• Radioactive elements have always existed on Earth and in outer space

• However, human activity has added to the amount of radiation that humans are exposed to on Earth

What is background radiation?

• Background radiation is defined as:

The radiation that exists around us all the time

Sources of background radiation

• There are two types of background radiation:

  • Natural sources

  • Man-made sources

Composition of background radiation

• Every second of the day there is some radiation emanating from natural sources within our environment and from space, such as:

  • Rocks

  • Cosmic rays from space

  • Foods

• Man-made sources of radiation increase the background radiation levels, examples include:

  • Fallout from nuclear weapons testing and nuclear accidents

  • Exposure to medical testing and devices, e.g. X-ray machines

Corrected count rate

• Background radiation must be accounted for when taking readings in a laboratory

• This can be done by taking readings with no radioactive source present to find the background radiation and then subtracting this from readings with the source present

  • This is known as the corrected count rate

Variation in background radiation

• The level of background radiation varies across the planet and depends on:

  • Altitude

  • Geology of the rocks

  • Proximity to nuclear power stations

  • Use of nuclear weapons

Radon gas from rocks and buildings

• Airborne radon gas comes from rocks in the ground, as well as building materials e.g. stone and brick

• Levels of radon gas are generally very low and are not a health concern, but they can vary significantly from place to place

  • For example, some areas may contain rocks and soil which emit higher concentrations of radon gas, such as Wales and Cornwall

Radon concentration map of the UK

Nuclear fallout from nuclear weapons

• Fallout is the residue radioactive material that is thrown into the air after a nuclear explosion, such as the bomb that exploded at Hiroshima

• While the amount of fallout in the environment is presently very low, it would increase significantly in areas where nuclear weapons are tested

Nuclear accidents

• Nuclear accidents, such as the incident at Chernobyl, contribute a large dose of radiation to the environment

• While these accidents are now extremely rare, they can be catastrophic and render areas devastated for centuries