How are the cores of nuclear power plants constructed?

Question

I’m watching Chernobyl on HBO and they’re describing the different areas of the building after the explosion, some of which they say would kill you within days or weeks due to the high level of radiation. They also talk about how they can’t even use robots to clean the material up because the extreme radiation will shred the circuitry of the robots. So, how on earth are these things constructed in the first place?

In: Engineering

Answer 1

There are many different designs of reactors and it’s too long to list to explain each one. What makes reactor cores dangerous is fuel that’s either partially irradiated in the core or spent fuel that’s no longer in the core. Different reactors use slightly different fuels, but the main component of the fuel is uranium. In most reactors, the fuel is composed of pellets stacked into [rods](https://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Fuel_Pellet.jpg/553px-Fuel_Pellet.jpg), and then the rods combined into [larger assemblies](https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/fuel-assembly-new.gif). Prior to being placed in the reactor, the fuel is *relatively* safe, since it’s just uranium or some uranium compound. In fact, you can hold a chunk of uranium in your hand and be fine.

What makes it so dangerous is the fission process that turns the uranium into energy also, as a byproduct, creates many more radioactive isotopes that are far more dangerous than the original uranium fuel. This process also irradiates all of the non-fuel components of the core, so the core has have heavy shielding (usually several meters of steel and concrete) to keep the radiation inside. This also means that you need some mechanism to keep radiation from escaping while removing spent fuel and adding new fuel to the core.

So back to your question, the core itself is different each reactor design, but it’s still just made out of mostly normal construction materials concrete and steel. Fresh fuel is also mostly safe to handle. It’s partially or fully used fuel that’s dangerous. With adequate shielding, it’s not problem.