Any material used to attenuate radiation. Gamma rays need dense or thick material such as lead, steel, concrete or water; for cobalt-60 a lead thickness of roughly 1.2 cm halves the dose rate, the half-value layer. Beta particles stop in plastic or a few millimetres of metal, alpha in paper or skin, and neutrons need hydrogen-rich materials such as water or polyethylene. Temporary shielding during outages is usually lead blankets, lead wool or water-filled shields.
Hang four layers of lead blanket on the RHR elbow, that should drop the general area by half.
Temporary lead adds load that pipe supports were never designed for, so shielding packages need an engineering check before they go up.
Also heard as
- shield
Related terms
Time, distance, shielding
The three basic ways to cut external dose: spend less time near a source, stay farther away and put material in between.
ALARA
As low as reasonably achievable: the principle of keeping doses as low as practical, not just below limits.
Shine
Radiation reaching a spot from a nearby source, through a gap or by scattering, rather than from what is being worked on.
Hot spot
A small spot on piping or equipment with a much higher dose rate than its surroundings.