One of the most commonly asked questions is, “What lead thickness do I need for radiation protection?” There is no hard and fast rule, as adequate shielding must account for several variables such as length of exposure, distance from the radiation source, and the intensity and type of radiation.
The harmful effects of ionizing radiation on the human body are well understood. If you work in a radiologic environment, personal protective equipment (PPE) and appropriately placed barriers are essential. Garments such as a lead apron and thyroid shield are the most basic, yet effective radiation protective devices for procedures using x-ray and gamma-ray radiation.
Any radiology facility should have its lead shielding requirements evaluated by a qualified radiation safety expert, as defined by the National Council on Radiation Protection and Measurements (NCRP) or your local authority. Read on to learn more about lead shielding thickness for radiation protection.
Lead Properties and Materials
Lead (Pb) is a soft, grayish metal. Each atom contains a nucleus with 82 protons surrounded by a tightly held electron cloud of 82 electrons, giving it the highest atomic number of the non-radioactive elements.
The most remarkable property of lead is its density—it’s really heavy! The atoms form a tightly-packed metallic lattice that is durable, resists corrosion, and can absorb ionizing x-rays and gamma rays in a process called attenuation.
The drawbacks are that it is toxic and accumulates in the body. Repeated exposure results in cumulative poisoning, inducing cognitive deficits and kidney disease. Lead dust is an environmental hazard. Disposal requires special protocols to protect humans and ecosystems.
Lead is highly malleable, friable, and ductile. It can be shaped into many forms including foils, wools, pipes, sheets, bricks, and slabs. It can be alloyed with other metals such as antimony, or embedded in ceramic, glass, epoxy, and plastic matrices.
Processing of Lead
Lead occurs naturally in various ores, the most common being lead sulfide or galena. Mined ore is finely crushed to start the extraction process:
1. Flotation:
The crushed ore is mixed with water to form a slurry. Added pine oil attracts the sulfide component and the air is bubbled through the mixture. The frothy pine oil and sulfide mixture float to the top, while the waste rock or gangue sinks to the bottom.
2. Filtering:
Alum and lime aggregate the metal particles into larger clumps, and xanthate makes them float. The slurry is filtered to produce a concentrate of 40–80% lead.
3. Roasting:
The concentrate is mixed with sand, limestone, and coke on a moving grate. Air heated up to 2,550°F (1,400°C) is blown through the grate. Any remaining sulfur combusts to form sulfur dioxide. The roasted ore fuses into a brittle sinter that is broken up into lumps.
4. Blasting:
The sinter is put into a blast furnace and heated to about 2,200°F (1,200°C). This produces 95–99% pure molten lead called base bullion. This is drawn off into molds called drossing kettles.
5. Refining:
The drossing kettles maintain the lead just above its melting point of 621°F (327°C). A small amount of zinc draws metals such as gold or silver to the surface as a dross to be skimmed off.
6. Casting:
The refined lead is now close to 100% pure. It is cooled and cast into ingots weighing up to a ton. These can be shaped, rolled, extruded, and molded into a wide variety of final products.
Lead Thickness for Attenuation
Gamma rays and x-rays can travel miles in the air and penetrate deep into the human body or pass right through it. Lead shielding can prevent or reduce radiation by attenuation.
Here are some recommended thicknesses of lead to stop radiation in different facilities:
- Dental practice – 1/32“ (0.3mm).
- Veterinary practice – 1/32” (0.35mm) to 1/16” (0.5mm).
- Medical facility or non-destructive testing lab – 1/16” (0.35mm) to 1/8” (0.5mm).
- Nuclear facility – 1/8” (3.2mm) or greater.
Let’s examine categories of leaded attenuating products:
1. Barriers and Panels:
Cold rolled lead sheeting, from thin foil to sheets more than 2” thick, is laminated in radiation shielding barriers and panels.
- Barrier Technologies manufactures windowed mobile barriers with 1.6mm Pb equivalence @150kVp.
- Our maximum protection Terminator XR™ provides 1.0mm Pb equivalence per panel and 2.0mm in overlaps, for 100% attenuation @160kVp.
2. PPE, Drapes, and Shields:
Rolled lead sheeting is also used as a liner for radiation-protective garments and accessories. In most of these, the lining offers 0.25 to 0.5mm Pb equivalence.
- Barrier Technologies manufactures lead aprons with 0.35mm or 0.5mm Pb equivalence.
- Our table drapes, blankets, portable shields, and thyroid collars have 0.5mm Pb equivalence.
3. Leaded Glass:
Lead oxide of 2–28% by weight is added to potash glass. Leaded glass is extensively used for attenuating viewing windows, cathode ray tube shielding, and specialized eyewear.
- Barrier Technologies radiation-protective glasses are fabricated in partnership with Corning and their Med-X line of 0.75mm Pb equivalence radiation protective lenses.
Lead Thickness Chart
Half value layer (HVL) is the thickness of lead to reduce the dose to 50%. The tenth value layer (TVL) reduces the dose to 10%.
| Peak Voltage (kVp) | HVL (mm) | TVL (mm) |
|---|---|---|
| 50 | 0.06 | 0.20 |
| 100 | 0.27 | 0.90 |
| 150 | 0.30 | 1.00 |
| 200 | 0.52 | 1.73 |
| 300 | 1.47 | 4.88 |
| 400 | 2.50 | 8.30 |
| 1000 | 7.90 | 26.23 |
Quality Lead for Radiation Protection
Versatile lead has excellent attenuation properties and is considered the gold standard for radiation shielding. It’s important to know the lead thickness for radiation protection required for your specific laboratory or healthcare facility. This requires understanding concepts such as attenuation and researching protection products for shielding radiation-controlled areas and people.
Barrier Technologies offers expert advice and consultation to assist you in finding the radiation protection that suits your needs. Our in-house technical staff will assist you throughout the process. Whatever your requirements, we’ll come up with innovative and practical solutions to ensure your safety from the hazards of ionizing radiation.
Please browse our catalogs of lead radiation protective apparel, barriers, eyewear, and other accessories. Our research and development team is constantly coming up with cutting-edge products and materials. Not only do these offer unsurpassed protection, but they also do it with style, comfort, and ease of use! Contact us for more information.
