Background radiation and radiation dose

Background radiation

Radiation that is around us all of the time

Sources of background radiation

Natural sources such as rocks and cosmic rays from space and man-made sources such as the fallout from nuclear weapons testing and nuclear accidents

Factors affecting exposure to background radiation

Location and occupation among other things

Activity

The number of decays per second from an unstable nucleus

Becquerel (Bq)

The SI unit for activity

Why activity is unsuitable to measure radiation exposure

The activity of two sources could be the same, but one could emit alpha whereas the other emits beta (so they would each have a different effect on a person)

When alpha radiation is more dangerous to a person than beta

When the radioactive source is inside the body

Why alpha radiation is more dangerous to a person than beta when inside the body

An alpha particle is more ionising and it cannot penetrate the skin so will not be able to escape from the body

When beta radiation is more dangerous to a person than alpha

When the radioactive source is outside the body

Why beta radiation is more dangerous to a person than alpha when outside the body

A beta particle is less ionising but it can penetrate the skin so will be able to pass into the body

Radiation dose

A measure of the amount of damage that would be caused by the absorption of 1 joule of energy per kilogram of body mass

Sievert (Sv)

The SI unit for radiation dose

Millisievert (mSv)

A more commonly used unit for radiation dose, as absorption is usually less than 1 Sv

1 sievert (Sv) is equal to \_____ millisieverts (mSv)

1,000 millisieverts (mSv)

Radiation dose from eating a banana

Approx. 0.00001 mSv (if it contains radioactive potassium)

Radiation dose from 3 months on the ISS (International Space Station)

40 mSv

Typical radiation dose that can lead to death

10 Sv (10,000 mSv)