Radiation Shielding

Radiation shielding is used to block or attenuate the intensity of alpha particles (helium atoms), beta particles (electrons), X-ray radiation, and gamma radiation (energetic electromagnetic radiation). It reduces the intensity of incident radiation by introducing a radiation-absorbing medium. The material and thickness of the radiation shield determine its effectiveness. Specifications for radiation shielding include material (e.g., lead, tungsten), thickness, purity of material (99.94% lead, etc.), and rated energy range of radiation blocked or attenuated (100 to 300 keV). Features (such as liquid-cooling) and applications are also important to consider. Many radiation protection products are listed or approved by organizations such Underwriters Laboratories (UL) or Underwriters Laboratories Canada (ULC).

There are many types of radiation shielding. Most products are made of lead, a bluish-white, high-density, heavy metal that can effectively attenuate alpha rays, gamma rays, and X-rays. Lead shielding is a type of radiation shielding that includes lead aprons, lead barriers, lead-lined blankets, lead bricks, lead curtains, lead-lined cabinets, lead-lined doors, and rolled lead sheet. Lead aprons are protective garments worn by medical personnel and patients during X-ray procedures. Lead barriers and lead blankets are used to cover patients or medical equipment. Lead bricks are used for both positron emission tomography (PET) shielding and linear accelerator shielding. These radiation shielding products are also used in gamma knife rooms and in high dynamic range (HDR) imaging.

Lead is also used in radiation shielding products such as lead curtains, lead-lined cabinets, lead-lined doors, and rolled lead sheet. Lead curtains are lined with vinyl and designed for use in medical facilities where secondary or low-level radiation is present. Lead-lined curtains may come equipped with a track and trolleys. Lead-lined cabinets and other lead-lined laboratory furniture are designed to store radioactive material and other radioactive inventory. Lead-lined doors are faced with wood, but have a thick layer of lead sheeting in the center. Rolled lead sheet is formed by moving a slab of refined lead between the rollers of a rolling mill. After the sheet is cut to size, the rolled lead is packed and shipped to suppliers of radiation shielding for use in various products.

Although it used in many types of radiation shielding, lead is ineffective against the high-energy electrons present in beta radiation and neutron radiation. Consequently, high-energy shielding is required in some medical and laboratory applications. For example, high-energy shielded decay drums are used to store high-energy radiopharmaceuticals. Nuclear medicine supplies and accessories also include X-ray shielding glass, a mirror-polished and scratch-resistant barium-type lead glass that is used in airports and other facilities that perform radiation screening.

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• Enclosures
  Planning for packaging and interconnections in the early phases of a design project eliminates the chances of poor design degrading long-term reliability. The integrity of system design depends on the...
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