Eli5:Where does radiation disappear to in storage areas?


Bit iffy to explain, but radiation can penetrate cells in some cases and damage the cell. But what happens to the radiation energy coming from decaying material in safe underground storage areas?

In: Physics

Everything eventually turns into heat energy. When it is underground, the radiation has a far way to travel before it hits something that isn’t dirt or concrete. It doesn’t disappear, it dissipates. It gets spread out as heat energy over a huge area and basically becomes unnoticeable. Like food dye drops in the ocean.

The reason that radiation damages cells is because it focuses a large amount of energy in a small area.

Lets say you have something that emits 1 watt of radio waves and 1 watt of x-rays. The radio waves are spreading that 1 watt of energy over an area that may be hundreds of square miles just due to the size of the wave. On the other hand, the x-rays spread that same amount of energy out over about a square nanometer.

That energy ultimately gets turned into heat, but the heat from the radio wave is spread out over such a huge area that nothing inside that area is going to measurably heat up. However, the x-ray is heating up such a small area that whatever is in that area is going to heat up a lot – possibly to thousands or tends of thousands of degrees in a fraction of a second.

When you heat the complex biological molecules that your cells depend on to function by thousands of degrees they break apart. While high energy radiation doesn’t affect the vast majority of the stuff in one of your cells your cells are dependent upon certain molecules remaining stable to function – such as your DNA. If even a tiny amount of a cell’s DNA breaks apart that can kill the cell. And that’s ultimately why high energy radiation is dangerous – it doesn’t damage the vast majority of the cell or even the vast majority of the DNA in the cell. But sometimes it causes just enough DNA damage that your cell can’t repair it and the cell dies.

If you have a radioactive source buried underground the radiation from that source is being absorbed by the surrounding dirt. It heats the dirt molecules up in the same way that it heats the molecules in your cell up. Its just that dirt doesn’t rely on being composed of an incredibly complex chemical mixture to exist. If you heat dirt up, even to thousands of degrees, nothing really happens. It just cools back down and its still dirt.