Lead shielding

Lead shielding refers to the use of lead as a form of radiation protection to shield people or objects from radiation so as to reduce the effective dose. Lead can effectively attenuate certain kinds of radiation because of its high density and high atomic number; principally, it is effective at stopping gamma rays and x-rays.

Lead's high density is caused by the combination of its high atomic mass and the relatively small size of its bond lengths and atomic radius. The high atomic mass means that more electrons are needed to maintain a neutral charge and the small bond length and a small atomic radius means that many atoms can be packed into a particular lead structure. Because of lead’s density and large number of electrons, it is well suited to scattering x-rays and gamma-rays. These rays form photons, a type of boson, which impart energy onto electrons when they come into contact. Without a lead shield, the electrons within a person’s body would be affected, which could damage their DNA and cause cancer. When the radiation attempts to pass through lead, its electrons absorb and scatter the energy. Eventually though, the lead will degrade from the energy to which it is exposed. However, lead is not effective against all types of radiation. High energy electrons (including beta radiation) incident on lead may create bremsstrahlung radiation, which is potentially more dangerous to tissue than the original radiation. Furthermore, lead is not a particularly effective absorber of neutron radiation.

Lead is used for shielding in x-ray machines, nuclear power plants, labs, military equipment, and other places where radiation may be encountered. There is great variety in the types of shielding available both to protect people and to shield equipment and experiments. Personal shielding includes lead aprons (such as the familiar garment used during dental x-rays), thyroid shields, and lead gloves. There are also a variety of shielding devices available for laboratory equipment, including lead castles, structures composed of lead bricks, and lead pigs, thick containers for storing and transporting radioactive samples.

...
Wikipedia