If I'm not mistaken that's 0.1137 milisievert / hour. Meaning you have to stand glued to the tiles for about 4 years to get the LD50 lethal dose of about 4000 Sievert. Also, the lethality of the dose only really applies when the exposure is short.
Or, alternatively, the average yearly background radiation of about 2 milisievert takes about 18 hours of being glued to those tiles.
The real danger is the tiles, it's that throws something hard, shatters one of the tiles, releases dust, and someone breathes the dust in.
I'm actually astounded this is allowed to be there in a public place, because at home you can reasonably expect protect against someone shattering a tile, but in public? One drunk guy is all you need.
That's most likely the reason they are still there, because of how much more hazardous it would be to attempt to remove them.
Then again there are well practiced methods for removing sources of similarly hazardous air-bourn particulates such as asbestos, i'm not sure how much difference there is between the two beyond the low risk of pure exposure (inhalation being the serious risk here).
> Then again there are well practiced methods for removing sources of similarly hazardous air-bourn particulates such as asbestos, i'm not sure how much difference there is between the two beyond the low risk of pure exposure (inhalation being the serious risk here).
There's also the difference that this is a U-Bahn station in use, in the rough middle of a line. Closing it down for a prolonged period of time, and fully sealing it from the rest of the line to avoid the spread of dust through the metro tunnels would be a significant and disruptive undertaking.
Even if it happens from time to time, the amount of dusk is going to be ridiculously small (you don't release that much dust from damaging a rock, let alone glazing, unless you grind it).
And keep in mind that this is a subway station, places where the pm2.5 levels are routinely extremely high because of the dust released by train breaks, so a microscopic amount of uranium dust is really negligible in such an environment.
I imagine some drilling would create quite a nasty cloud. Of course this would require being oblivious of composition by magistrate and allowing it, which I don't think is the case here. Still, at least put on it some hard transparent protective paint, I am sure there are things for that.
The average, of course, is just that, an average. There are some places that are naturally around 100 mSv dose annually, or some 50x higher, and places that are much lower than average. Under truly non-ideal conditions, like having a poorly-ventilated basement made out of uranium-rich limestone, it could probably get even higher than 100 mSv a year just from the radon.
Speaking of which, radon gas is the main way in which uranium affects the health of people. Depending where you live and the construction methods, it may be worth getting your basement checked, and ventilated properly if necessary.
Even the extreme scenario there is still far short of causing acute radiation sickness. People who live in such regions are sometimes exposed to such levels their whole lives, which can still be long and healthy. But not quite as long and healthy as those without such exposure, on average.
EDIT: Someone linked to the Wikipedia article for uranium tiles, which says that the majority of the radiation comes from the decay products and is beta radiation[1]. Beta radiation has a weighing factor of 1, which makes your calculation pretty much correct!
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EDIT 2: Looking more closely it appears that the dosimeter in the video is switched to µSv/h, so it's reading 0.1 mSv/h anyway and the whole discussion below can be skipped if you're not interested in the difference between Gy and Sv.
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If I remember my lectures correctly (Wikipedia did help me here), the conversion is 1 Roentgen ~ 00.1 Gray (Gy), which is a slightly different unit from Sievert (Sv).
1 Gy is 1 J/kg of absorbed energy, however the biological effects change depending on the type of radiation. Sv is Gy adjusted by a weighing factor. It's 1 for gamma rays, where 1 Gy = 1 Sv, but for alpha particles it's 20 [0].
Uranium-238 emits alpha particles, which get stopped by a few cm of air or even dead skin. So the effective dose you are receiving from the decay of U-238 is probably closer to 0 mSv/h.
Or, if you eat it and it's inside you, 2 mSv/h, at which point you should probably be quite worried.
The decay products of U-238 however are beta emitters, which changes the calculation again. The beta particles can penetrate the skin, but the weighing factor for beta radiation is 1, so it can reach you but is also less dangerous.
So what's the actual final value? I honestly don't know, radiation can be complicated, and I just wanted to share the difference between Gy and Sv!
An idea for Berlin police looking to move on those pesky loitering youths in the station, charge them with triggering an INES incident. (Giving themselves a dose of radiation exceeding annual limits by leaning against the wall.)
They are using different and not directly convertible units.
Roentgen (R) used by the instrument only measures exposure, but this is not the same as absorption which depends on the type of radiation, the type of biological tissue exposed, the duration of exposure etc. The parent is using Sv which measures absorption for the purpose of more usefully assessing biological risk. I'm not sure how the parent is converting them, there are probably some good rules of thumb.
Here's a screenshot of the highest reading I saw (11.37) and an english overlay of possible units it can display. It's hard to see the button positions.
They're switches, and it looks like it's set to mSv/h based on your English overlay. So 11.37 mSv/h, or .01137 Sv/h - about 4 1/2 times the level of the typical background radiation.
The overlay gets that position wrong -- it's µSv/h (microsieverts, the transliterated legend is "mkZv/ch".) 11.37 mSv/h would be a radiological incident. The Australian lost density gauge capsule from a couple of days ago was 2-5 mSv/h.
Hmm, 3 mSv is supposed to be the average annual background radiation absorption for humans [0], that's roughly 0.000342 mSv/h. Which would make 11.37 mSv/h 33245 times greater.
At the other end of the scale the minimum annual dose with a clear link to increased risk of cancer is supposedly 100 mSv [1]. But the risk is different depending on the distribution over time, so if we make it hourly for comparison that is 0.0114 mSv/h making this reading about 1000 times higher than that risk threshold (but the risk is over a year is effectively assuming continuous exposure).
Seconds or minutes isn't going to be terrible, but in only 9 hours leaning against it you would get a years worth of high risk cancer dose!... I'd stay away from the wall. happy to be corrected, this stuff is hard to interpret if you are not an expert. The falloff is really fast though, so it's basically harmless if you are just walking through... maybe the original intent was to stop people touching the walls :D like an electric fence without the need for power.
Background radiation is less than 3.5 mSv/year, or less than 0.0004 mSv/hour. So if these tiles radiate 11.37 mSv/hour that would be 28 000 times more than background radiation !
The LD50 would apply to effects of acute radiation sickness. However, given the long duration exposure, it would increase your relative risk of stochastic effects, like cancer.
11.37 mR/h? Not great, not terrible.