A few days ago, a Reddit user had one of the worst summer camp afternoons you can imagine, when he literally dropped his phone into a nuclear reactor.
He was visiting the McClellan Nuclear Research Centre in California, stuck his phone over the railing to take a picture of the pretty, glowing water, and, yep, dropped it in.
It's definitely not the worst thing that could happen at a nuclear reactor - and, of course, this is Reddit, so he could be making this story up.
But, if it's true, dropping your phone in any large body of water - especially once as closely guarded as a radioactive research facility - is pretty terrible... and embarrassing.
"The room was quiet for about 10 seconds and everybody was just taking in what the hell just happened and watching my phone sink slowly," Reddit user stanthepan wrote on the Today I Fucked Up (TIFU) subforum.
"Luckily it's not the operator's first rodeo, he pulls out a swimming pool net and swoops it up and hands it to me. Now I'm feeling like a dumbass and hoping my 'waterproof' s5 will hold its own against some reactor water."
He was expecting it to be pretty quickly fried by all that radiation, but his phone came out of the experience surprisingly well - he even used it to write the Reddit post - and the reason why is a good lesson in nuclear physics for all of us.
Even though the pools of water surrounding nuclear reactor cores look radioactive, they usually contain less radiation than the surrounding air.
First up, the core uses a fuel such as uranium to initiate and control a sustained chain reaction of atom splitting, which releases a whole heap of energy in the process.
Most of the high-energy particles produced by this reaction are reflected within the core to keep the whole thing going. And in research reactors such as McClellan, housed at the University of California, Davis, some of these particles are also beamed out into labs so they can be used for imaging studies, and to help scientists better understand the composition of materials.
But occasionally a high-energy particle will escape the core and, instead of entering the air where it could travel long distances, will smack into a pool of water, which slows it right down and produces something of a visual shockwave in the form of a blue glow, called Cherenkov radiation.
So unless you're swimming in the water directly surrounding a nuclear core, you're going to be fine.
But what about all the heat that water is absorbing, you might ask? Reactor pools aren't actually as hot as you might imagine - most research reactor pools sit around a comfortable 35°C, and would shut down if they hit around 50°C.
As XKCD explains, if you were planning on swimming in the water surrounding spent nuclear fuel, you'd be far more likely to be shot by guards on your way there than actually killed by radiation.
So, stanthepan's phone lives to selfie another day. On the way out of the tour, he and his phone were scanned to check how much radiation they'd been exposed to during their visit, and it was just 0.9 millirads.
To put that into perspective, you could be exposed to up to 100 rads without really experiencing any health effects.
Oh, and in case you're wondering, here's the photo stanthepan took before dropping his phone. Worth it:
His full post is below (and you really need to head over to Reddit to read the terrible radiation puns in the comments):
"This takes the cake for the clumsiest thing I've ever done. So I'm at a summer camp studying nuclear technology, and we got a field trip to go see the McClellan nuclear research facility. We get in the building, one of the reactor operators takes us up the stairs to the tank (the core is visible from the top of the tank).
The tank happens to be open from the topside, and the operator takes us right over on a metal grid standing over the tank. Now over here I'm thinking 'holy shit I'm gonna fall in', because my swimming skills are next to nonexistent and I prefer not drowning while being exposed to a clusterfuck of nope radioactive shit.
After giving all of us a rundown of how the reactor works, the operator cuts the lights so we can see the deep blue core at the bottom of the tank. Everyone starts pulling out their phones and snapping away, and you can probably guess what happens next here.
The room was quiet for about 10 seconds and everybody was just taking in what the hell just happened and watching my phone sink slowly. Luckily it's not the operator's first rodeo, he pulls out a swimming pool net and swoops it up and hands it to me.
Now I'm feeling like a dumbass and hoping my 'waterproof' s5 will hold its own against some reactor water. Turns out it functions enough for me to write this post, but believe me when I say my friends will never drop this (pun intended)."