Noadswood Science, 2012

To understand what makes a radioactive source appropriate for its use

Wednesday, April 19, 2023

The Geiger-Muller tube detects radiation – it is a metal tube filled with gas which has a thin wire down the middle and a voltage between the wire and the casing – it can detect alpha and beta, but not gamma

Radioactive sources are used in a variety of ways, from industry to schools, hospitals to the home…

The source that is chosen need to emit the correct type of radiation and have a suitable half-life

Some radioactive sources are found within: -• In smoke detectors• For sterilising medical instruments• For killing cancer cells• For dating rocks and materials such as archaeological

finds• In chemical tracers to help with medical diagnosis• For measuring the thickness of materials in, for example,

a paper factory

For devices which you want to last a long time a large half-life is needed…

Sterilising machines in hospitals use gamma radiation to kill bacteria on medical instruments – they use a powerful radioactive source with a long half-life, so that it lasts for a long time

For devices which you want to last a long time a large half-life is needed…

Smoke detectors use a weak source of alpha radiation to ionise the air between two electrodes which causes charged particles to carry the current through

If there is a fire the smoke absorbs the radiation, stopping the current and sounding the alarm

A source with a fairly long half-life is used so the detectors will work for a long time (and as it is alpha radiation it is stopped by a few centimetres of air so is safe)

Doctors may use radioactive chemicals called tracers for medical imaging

Certain chemicals concentrate in different damaged or diseased parts of the body, and the radiation concentrates with it

Radiation detectors placed outside the body detect the radiation emitted and, with the aid of computers, build up an image of the inside of the body

When a radioactive chemical is used in this way it is not normally harmful, because:• It has a short half-life and so decays before it can do

much damage• It is not poisonous

Emitters of beta radiation or gamma radiation are used because these types of radiation readily pass out of the body, and they are less likely to be absorbed by cells than alpha radiation

A tracer is a small amount of radioactive material used to detect things such as a leak in a pipe…

Gamma source

The radiation from the radioactive source is picked up above the ground, enabling the leak in the pipe to be detected

Radiation is used in industry in detectors that monitor and control the thickness of materials such as paper, plastic and aluminium

The thicker the material, the more radiation is absorbed and the less radiation reaches the detector which sends signals to the equipment that adjusts the thickness of the material…

The thicker the material, the more radiation is absorbed and the less radiation reaches the detector which sends signals to the equipment that adjusts the thickness of the material…

It is vital to always act to minimise the exposure to a radioactive source

Never allow skin contact with a source – always handle with tongs

Keep the source at arm’s length (as far from the body as possible)

Keep the source pointing away from the body

Always keep the source in a labelled lead box, and put it back as soon as the experiment is finished (keeping the exposure time to a minimum)

Industrial nuclear workers wear full protective suits to prevent tiny radioactive particles from being inhaled (or lodging under the skin / under fingernails)

Lead-lined suits, lead / concrete barriers, and thick lead screens prevent exposure to gamma rays from highly concentrated areas

Workers also use remote-controlled robot arms to carry out tasks in highly radioactive areas