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Do you know anyone who ' d like to learn a bit more about radiation ? These pull-out sheets will help .

Shielding materials for radioactive sources

Sources can require little to extensive shielding to allow people to work safely around them . The amount and type of shielding depends on the amount and type of radiation emitted by various radionuclides , and how close people need to be to the source .

The diagram below shows the effectiveness of different materials to reduce transmission of the main types of radiation .

As you can see , alpha radiation is easily shielded with paper or clothing but is very dangerous if its particles are inhaled . Shielding is therefore not required for sources that only emit alpha radiation . Beta transmission can be attenuated to safe levels of radiation with thin layers of

Alpha

Beta

Gamma or X-ray

Neutron

Neutron

Paper or clothing

Few millimetres of aluminium or thin lead

aluminium or lead . An example is the use of Phosphorus-32 in research laboratories . P-32 emits high energy beta radiation , but 10mm of clear acrylic plastic is very effective at shielding it and also allows operators to see what they are working on .

Gamma or X-ray radiation is more penetrating and requires very dense material to shield it . The half value layer is the thickness of material required to reduce the intensity of incident radiation by half .

The table overleaf shows the half value layer of different materials for shielding gamma radiation emitted from different radionuclides commonly used in sealed sources .

Bremsstrahlung radiation

Dense materials , e , g . Several centimetres of lead or metres of concrete

Secondary gamma radiation may require additional shielding

Material of low atomic number , e , g . hydrogen-rich material such as water , polyethylene or paraffin wax

Secondary gamma radiation

Gamma , X-rays and neutrons only attenuated , not completely absorbed

Radiation Protection Today Summer 2022 35