OCR Gateway B Science Additional Higher P4- Uses of radioisotopes

What is background radiation?

Ionising radiation always present in the environment

Why does background radiation not cause harm?

The levels are constant and are too low to be harmful and are naturally occuring mostly

Main contributors to background radiation?

Cosmic rays from the sun, decay of rocks, radon gas from the ground

Small contributors to background radiation?

Man made sources like radioactive waste from nuclear power stations and hospitals, and from smoke alarms

How much does human activity contribute to background radiation?

Less than 1%

What is the most common radioisotope used in smoke alarms?

Americium 241

What type of radiation do smoke alarms give out?

Alpha

How does a smoke alarm work?

The alpha particles ionise the molecules of the air forming ions and electrons which are attracted to a pair of charged plates as shown in the picture below. When the ions and electrons hit the plates they provide a small amount of electricity (a small current). This current stays constant and is monitored by the smoke alarm.When smoke enters the smoke detector, the smoke particles near to the radioactive source absorb many of the alpha particles before they can ionise the air between the charged plates. The number of ions and electrons between the charged plates therefore decreases and so the current which is passed between the charged plates also decreases. The smoke detector notices the decrease in current and sets off the alarm.

How is gamma used in pipe tracers?

Gamma tracers allow us to detect a leak in a pipe and where it is. Firstly gamma tracer is aded to liquid in the pipe . A detector is moved along the ground above the buried pipe. The count rate on the…