Why is lead used to protect yourself from radiation

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Why is lead used to protect yourself from radiation

In: Chemistry

It does not allow radiation through it. It’s not really that effective when it comes to large scale radiation like the one at Chernobyl, but yeah, it helps.

The density of lead stops most of the radioactive (and other) particles from penetrating, depending on the thickness.

Imagine holding a flash light next to tissue paper, and then same light through a wall. Notice some light goes through in tissue but nothing in wall? Basically gamma radiation (most dangerous) can go through a lot of things like a light through tissue.but lead or other heavy materials are too dense and no gamma particles go through to hurt us. Different radiation has different penetration abilities, alpha can not pass skin, beta bare through a few layers of the body, and gamma goes through as if the human didnt even get in it’s way and it will destroy our precious DNA.

Lead is commonly used to stop photon radiation because:

* It is very dense, so we need less material to achieve the same effect.

* It has a high Z number. That means, lead nuclei are large, which means that they absorb lower energy photons much much better. Note that this point typically goes hand in hand with the first point (large Z → high density).

* It’s cheap and available.

With that said, other materials fulfill these requirements as well, and are used here and there. For example tungsten is often used instead of lead because it’s not as toxic. In radiography we use “lead aprons”, however these do not contain lead, but something else (company secret!) because of the toxicity of lead. Ironically, depleted uranium has also sometimes been used as a radiation shield.

While the high density of heavy metals mean they will absorb most radiation regardless, a high Z number is bad for neutron (and charged particle) absorption. For these types of radiation, low Z materials are preferable, such as water. For this reason, we usually try to have different layers of shielding, e.g. first some lead, then some plastic water, then some lead again, etc. You have to think about how to order the materials, because high energy photons tend to release neutrons when interacting with high Z materials, so you don’t want to have water first, and then lead only. For projects where we don’t expect a lot of photon radiation (e.g. proton therapy clinics) we just use really thick concrete walls. Concrete contains a lot of water, so it’s a good choice.

In nuclear power plants we usually shield the reactor and the waste with water. This is for practical purposes. Water is like the worst material out there for gamma ray absorption, however it is still very practical to work with because it’s a harmless, cheap, liquid, and also absorbs neutrons.

Imagine a net with holes big enough to let a ball through. You throw a ball at this net with big holes and it usually goes through. Sometimes it bounces back because it hits the net.

Now imagine a different net with smaller holes that the ball won’t fit through. Now the net will stop the ball. Sometimes the ball will get stuck in the net.

With that in mind, imagine the ball is some kind of radiation and the net is made of lead. Different radiation will either bounce off the lead because the holes are too small or pass through because the holes are big enough. Sometimes the radiation will bounce because it hits the lead.