Background radiation
When unstable atoms give off particles that can be harmful to humans. materials occur naturally and, as a result, everyone is exposed to a low-level of radiation every day. This exposure comes from a mixture of natural and man-made sources.
The actual amount of Energy carried by particles from a radioactive substance, or spreading out from a source. that a person is exposed to depends on where they live, what job they do and many other things.
Scientists must always take into consideration the amount of Low level nuclear radiation that is always present from natural and man-made sources, eg cosmic rays from the Sun, radioactive rocks in the Earth's crust, radioactive radon gas in the air. when working or experimenting with radioactive sources and discount it from their results.
Background radiation affects everyone mainly by Process of exposing an object to a source of radiation. Eg fruit exposed to gamma rays in order to destroy bacteria is said to have been irradiated., but a small amount is from being A substance is contaminated if another substance is mixed or dispersed within it. by An isotope of an atom of an element that releases ionising radiation. Isotopes of an element have more or fewer neutrons than each other. Also called a radioactive isotope. in the food and drink that is consumed.
Measuring amounts of radiation
The simplest measure of radioactivity is the Becquerel (Bq). This is a measure of the The number of decays of a radioactive element per second. Measured in Becquerels (Bq). of the The central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei.. The activity is the number of decays per second from an unstable nucleus.
A source that Energy is 'given-out' by the material and the internal energy of the material will decrease. For example, infrared radiation from the Sun is emitted into space. one particle per second has an activity of one Bq. However, this particle could be A type of ionising radiation consisting of 2 protons and 2 neutrons. or A type of ionising radiation consisting of a single electron. and would, therefore, have a different effect on a person鈥檚 body.
- a beta particle has a lot of energy but may not cause a lot of damage because of its low Process by which electrons can be added or removed from an atom to create an ion. power
- an alpha particle will have less energy but will cause more damage in a shorter distance because it is bigger
The Sievert (Sv) is the unit to measure radiation dose and is the amount of damage that would be caused by the absorption of 1 joule of energy in each kilogram of body mass.
Typically, absorption is less than 1 Sv, so milliSieverts (mSv) are often used instead. 1,000 mSv = 1 Sv.
Some example doses are shown below:
| Eating a banana that contains radioactive potassium | 0.000000098 Sv | 0.000098 mSv |
| Exposure for cabin crew on airliners (per year) | 0.0016 Sv | 1.6 mSv |
| 6 months on the International Space station | 0.08 Sv | 80 mSv |
| Highest dose to a worker during Fukushima disaster | 0.67 Sv | 670 mSv |
| Typical fatal dose | 10 Sv | 10,000 mSv |
| Eating a banana that contains radioactive potassium |
| 0.000000098 Sv |
| 0.000098 mSv |
| Exposure for cabin crew on airliners (per year) |
| 0.0016 Sv |
| 1.6 mSv |
| 6 months on the International Space station |
| 0.08 Sv |
| 80 mSv |
| Highest dose to a worker during Fukushima disaster |
| 0.67 Sv |
| 670 mSv |
| Typical fatal dose |
| 10 Sv |
| 10,000 mSv |