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Grand Canyon Visitors May Have Been Exposed To Radiation For Years (azcentral.com)
joeflies writes: Park safety manager Elston Stephenson provides details about buckets of uranium that exposed visitors to radiation, and the subsequent cover up. The radiation was detected by a teenager that brought a Geiger counter to the building, and was subsequently "cleaned" up by employees equipped with dish washing gloves and a broken mop handle. "If you were in the Museum Collections Building (2C) between the year 2000 and June 18, 2018, you were 'exposed' to uranium by OSHA's definition," Stephenson wrote. "The radiation readings, at first blush, exceeds (sic) the Nuclear Regulatory Commission's safe limits. [...] Identifying who was exposed, and your exposure level, gets tricky and is our next important task." Stephenson said he had repeatedly asked National Park executives to inform the public, but never got a response.
"According to Stephenson, the uranium specimens had been in a basement at park headquarters for decades and were moved to the museum building when it opened, around 2000," reports AZCentral. "One of the buckets was so full that its lid would not close. Stephenson said the containers were stored next to a taxidermy exhibit, where children on tours sometimes stopped for presentations, sitting next to uranium for 30 minutes or more. By his calculation, those children could have received radiation dosages in excess of federal safety standards within three seconds, and adults could have suffered dangerous exposure in less than a half-minute."
"According to Stephenson, the uranium specimens had been in a basement at park headquarters for decades and were moved to the museum building when it opened, around 2000," reports AZCentral. "One of the buckets was so full that its lid would not close. Stephenson said the containers were stored next to a taxidermy exhibit, where children on tours sometimes stopped for presentations, sitting next to uranium for 30 minutes or more. By his calculation, those children could have received radiation dosages in excess of federal safety standards within three seconds, and adults could have suffered dangerous exposure in less than a half-minute."
Uranium gives off alpha radiation, which is effectively stopped by the layer of dead skin cells on your body. If you ground it up into a talcum-powder consistency and snorted it, then you'd be in trouble, but anything less than that and you're fine.
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"The report indicated radiation levels at "13.9 mR/hr" where the buckets were stored."
"The commission lists a maximum safe dosage for the public, beyond natural radiation, is no more than 2 millirems per hour, or 100 per year."
If you spent a day (7-8h) around the bucket then you received your yearly dose. I would feel bad for anyone that worked there and received continuous doses.
https://xkcd.com/radiation/
The report indicated radiation levels at "13.9 mR/hr" where the buckets were stored, and "800 mR/hr" on contact with the ore. Just 5 feet from the buckets, there was a zero reading. The abbreviation, "mR" typically stands for milliroentgen, a measurement roughly equivalent to a millirem, according to the Nuclear Regulatory Commission.
So if there was no reading 5 feet from the buckets, then the radiation was most entirely alpha decay. Those buckets must have been hot. The bigger problem is that they left a huge bucket of poison around children. The radiation thing is mostly a scare tactic unless you lived within 5 ft of those buckets. Also, I'm surprised they gave the units of measure they did. If they had used effective dose (Sieverts) it would have been 20x higher and much more scary.
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13.9 mRem is 139 microsieverts. So using that chart, one hour of exposure is somewhere between "Approximate total dose received at Fukushima Town Hall over two weeks following accident" and "EPA yearly release limit for a nuclear power plant". And about a third of "yearly dose from natural potassium in your body". Not great, but it could be a lot worse.
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Well, yes. Uranium is an alpha emitter. You can generally protect yourself quite well from radiation from natural uranium (not enriched uranium) by, well, wearing clothes. If worse comes to worst, holding a piece of paper between you and the uranium would be sufficient. Or wrapping the uranium in a couple layers of decent quality toilet tissue....
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What all the parent posters and XKCD are missing is that it's not just the dosage, it's the manner of exposure. Temporary exposure to an xray machine stops the moment the machine is turned off. A bucket of uranium specimens may contain dust that can get inside the body. Thus it needs to be handled carefully to avoid that, and in this case it appears that the staff had little idea of what they were doing.
It's the old "banana equivalent dose" fallacy. The body processes and removes excess potassium, but caesium accumulates in certain organs and does long term damage, with the effects only becoming apparent years later.
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