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As human knowledge and technology progress, radiation is used more extensively in medicine and many other industries. Accordingly, there has been a surge in research into radiation-shielding materials. Amazing advances in the metallurgical and material sciences fields have produced a variety of new and interesting attenuating substances that guard against the harmful effects of ionizing radiation.
Radiation is truly a double-edged sword. It offers extraordinary benefits, but excessive and accumulated doses cause tissue damage and increase cancer risk. What protective materials can mitigate these hazards? Read on to learn more about the different radiation shielding materials.
How Do Radiation Shielding Materials Work?
Radiation shielding works on the principle of attenuation. This is the ability of a substance to reduce the energy of an electromagnetic wave or charged particle that impacts it. Materials with very tightly packed, heavy atoms or molecules have greater density and are better at attenuating potentially dangerous radiation.
What Is Attenuation?
There are two major mechanisms of attenuation:
- Absorption: This occurs with lower energy interactions. The shielding material takes up and dissipates the energy of the wave or particle impacting it.
- Scattering: This occurs with higher energy interactions. The shielding material deflects the wave or particle, changing its direction and reducing its momentum.
Here’s an analogy—think of an arrow fired at someone holding a shield. The arrow can lodge in the shield, which is absorption, or bounce off it, which is scattering. (However, because no shielding is perfect, the probability exists that the arrow penetrates through the shield, which is known as transmission.)
The best radiation shielding materials are those that absorb radiation rather than scatter it. The more electrons there are in a shielding material, the more effective its stopping power is. Scatter radiation has less energy than incident radiation, but still impinges elsewhere and is dangerous.
What Materials Block Radiation?
Any substance can block radiation. It depends on the thickness of the material and the intensity of the radiation. We refer to the “half value layer”. This is the thickness of material that stops half the incident radiation passing through it.
The table shows examples of the half-value layer:
| To stop 50% of a 100 keV x-ray beam, you need | ||||||
|---|---|---|---|---|---|---|
| Air | Water | Carbon | Aluminum | Iron | Copper | Lead |
| 3555 cm or 1340 ” | 4.15 cm or 1 ⅝ ” | 2.07 cm or 13∕16 ” | 1.59 cm or ⅝ ” | 0.26 cm or ⅛ ” | 0.18 cm or 1∕16 ” | 0.012 cm or 1∕256 ” |
To reduce the radiation by half again to 25% requires double the thickness listed in the table. This exponential relationship applies to all further reductions until attenuation approaches zero.
It’s easy to see why lead (Pb) is widely used for radiation shielding. However, tungsten (W) is denser than lead and better at shielding gamma rays! What materials block radiation also depends on the type of radiation. Interestingly, lead is completely transparent to neutron radiation, but it’s stopped by water!
Here are the different types of radiation and what shields them:
| The Different Types of Radiation | |||
|---|---|---|---|
| Type of Radiation | Properties | Medical Uses | Shielded by |
| 1. Alpha particles |  |
Unsealed source radiotherapy | Skin, paper |
| 2. Beta particles | Brachytherapy | Clothing, aluminum foil, plastic | |
| 3. X-rays | X-rays, CT scans, fluoroscopy | Lead, lead-composite, tungsten/bismuth-based amalgamates |
|
| 4. Gamma rays | PET imaging, gamma knife | ||
| 5. Neutrons | Fast neutron therapy | Water, concrete, borated polyethylene |
|
Which Is the Best Type of Radiation Shielding Material?
Choosing the best type of radiation shielding material depends on the type of radiation. This section specifically looks at x-ray and gamma-ray protection commonly used by radiologic professionals such as radiographers and physicians.
1. Traditional Lead Shielding
The most commonly used material for radiation shielding is lead. It’s the highest atomic number element that isn’t radioactive. With 82 electrons per atom, it’s excellent at blocking x-rays and gamma rays. This soft, malleable metal is very easy to form into many different products from thin foils to thick blocks.
Lead is used for shielding x-ray machines, nuclear power plants, labs, medical facilities, etc. It’s also extensively used in radiation personal protective equipment (PPE) such as aprons, gloves, thyroid collars, eyewear, and more.
Protective x-ray lead aprons vary from 0.25 to 0.5 mm in thickness, which attenuates from over 90% to 99% of the radiation dose respectively. Barrier Technologies® manufactures an extensive range of barriers, PPE, and accessories that use lead shielding.
2. Lead Composite Shielding
Although lead is the gold standard of protection, it’s really heavy! People wearing lead aprons may become fatigued and develop musculoskeletal problems. Lead composite or “Lead-lite” shielding lightens the load by mixing other materials with the lead.
Lead composite shielding is a blend of lead and other attenuating elements, including tungsten, bismuth, titanium, antimony, tin, and magnesium. This mixture can be embedded in polymers such as rubber and polyvinyl chloride (PVC) to impart flexibility.
Barrier Technologies supplies a full range of proprietary lead composite PPE, with the same equivalency protection levels of lead, but up to 25% lighter than lead only!
3. Lead-Free Shielding
Not only is lead very heavy, but it’s also a toxic element that requires special disposal protocols. These problems can be avoided entirely by using lead-free shielding.
New radiation-proof materials are made from amalgamations of the same metals used in lead composite shielding, but without any lead added. They are mixed with additives and binders to make them easier to form.
Barrier Technologies’ innovative engineers have developed radiation PPE lighter than lead. Our proprietary attenuation blend is more than 30% lighter than lead and is environmentally friendly, too!
We’re Here to Serve You
Deciding which radiation shielding materials you need is influenced by many factors. These include variables such as weight, thickness, and cost. Your most important priority is protecting people and the environment from the harmful effects of ionizing radiation. It’s vital that shielding is appropriate for the intended application.
Barrier Technologies are visionaries at the cutting edge of radiation protection research and development. We have the expertise and experience in materials science to offer you the best advice on designs and safety. If you want more information, our website and catalogs are excellent resources. Contact us today with your specific requirements.
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