u/Unlucky-Safety-2745

So I’ve recently started taking a chemistry course online, and ever since I’ve been getting videos and stories of Chernobyl popping up on my social media so I’ve started looking around for more information. I’ve watched the series and the movies, but what I want to know is why is this chemical so deadly, how does it affect the body? How quickly can it affect the body if you do get a large dose like being next to the core in Chernobyl. I also want to understand how nuclear energy is made, I know some very vague things like the uranium neutrons move very fast and collide with each other and share electrons… (something like that, I’m new to chemistry…)
I also don’t understand how the core in Chernobyl could’ve exploded and why is water used to cool the core down?

If anyone could provide me with links or videos to help explain, or you could even write a long comment and I will read it. I would be eternally grateful.
Sorry for the awful formatting, I’m on mobile