I personally consider an area dangerous if I need to undergo radiation decontamination after entering it, continue emitting radiation after decontamination, and need to seek medical attention. Maybe the nuclear regulatory bodies have differen definitions?
Bananas emit detectable radiation, so you should probably choose different thresholds of what causes you to consider something dangerous.
They will still try to decontaminate you of any radioactive materials they can scrub off as a matter of course, but 300 counts per minute, while noticeably higher than background radiation levels, is pretty benign in the grand scheme of things. The fact that you can still count individual radioactive emissions is incredibly good news compared to how bad things could be.
Especially since the reactor will have been shutdown for some time by definition, if the reactor cavity is open enough to fall into. Hopefully the low rate of radioactivity evidenced by the counts on the person's hair is matched by the level of radioactivity in the water.
And on that note, medical attention would also be provided as a matter of course after a fall like this, but it seems to me that the physical injury of falling some distance and possibly hitting metal on the way down is going to be more of a danger than the radiation, especially compared to the sources of radiation people naturally run into (especially cigarette smoke, whether primary or secondhand).
It can mean a lot of things, yes, but that is not the same as saying it doesn't mean anything. If the detector was pegged high you certainly wouldn't assume a neutral frame to the situation, you'd assume some kind of significant release of radioactive contamination and act accordingly until you had better data.
I think you're softly implying things are more dangerous than they actually are, possibly due to not understanding just how insanely risk averse the nuclear industry is in the US. You could jog around a reactor chamber every morning and under a "normal person's" risk tolerance, you would never, ever be exposed to any danger. That worker who fell in the reactor pool seems like they got a radiation exposure equal to approximately a dozen chest x-rays (it's ambiguous though because they don't specify what tool was yeilding 300 counts per minute, nor do they give the total mSv).
The NRC would make you attend training and get decontaminated if you had to cross a street if they operated the roads.
It's not open to the public, but workers have to go into dangerous places to do maintenance. The refueling process, for example, requires removing spent fuel rods and inserting new ones, and for that the core has to be opened. It's not running, i.e. fissioning, but it's still radioactive material (water included).
It seems reasonable and prudent to go through decontamination after this sort of thing, but if the worker had just gone home to their family soaking wet without changing, there would still have been close enough to zero risk to anyone (again, cleaning up and making sure this is the case is a very reasonable thing to do).
This sort of place is safe enough to bring your kid into without significant precautions (I got to do this as a kid—it was really cool). The biggest risk by far is drowning.
0) If you've not read this chart, do carefully read it: <https://xkcd.com/radiation/>. If you've read it before, take some time to carefully re-read it.
1) The guy's getting sent off to seek non-emergency medical attention. I bet you an entire American Nickle that that attention is almost entirely for injuries sustained in the fall, rather than for radiation exposure.
I get the feeling that you don't know how complicated calculating radiation exposure is. There are plenty of interest in fear mongering against nuclear. Almost all the people talking about how much radiation 300 CPM is have absolutely no idea what they are talking about. Some confuse total measurement units for rates; others are using just the wrong units; still others are talking about levels that are 1000x or 1000000x higher than 300 CPM.
Or to put it another way, 300 CPM (which is a rate) is less than how much radiation you get when on a flight, or how much radiation you get at higher elevations. Even giving a simple explanation of how to calculate Greys (the actual measure you are looking for) takes up the better part of a page. Hell, your bones are radioactive. Yet there are plenty of people posting that somehow the risk to this guy is radioactivity. In reality, his biggest problem is probably going to be finding a new job.
CPM doesn't mean anything, it's useless to compare it to anything without more information.
For his job, depends on the dose he took. In my country he would have been on benefits until the dose was calculated, then if possible, reintegrated in the team, or directed towards a new job if not (paid formation and everything). I've studied with a diver who couldn't work with radioactive trash anymore, he wasn't meant to be a SWE in the end, he now dive for unexploded WW2 stuff in the north sea/Baltic I think
In a way you are right, but in another way you are wrong. Background radiation is mostly gamma which is generally the most dangerous kind. Radiation at a nuclear plant is mostly alpha and beta which are less dangerous at the same CPM rates. So technically you are right, you have to calculate the absorption, but in practice you are wrong because at that rate, there is no way he absorbed enough radiation to be dangerous.
Yeah I stopped really looking at replies when I realized it was just a bunch of people telling me that falling in a nuclear reactor pool isn’t that bad and to go read the XKCD again if I don’t get it.
numbers matter. A human naturally gives off 0.2mSv/year. so basically you are emitting radiation right now, just very slowly. They had 300 counts per minute which would e around 6200 mSv year. But how much is that? the limit in a year for some body parts goes up to 500mSv year for workers. But that's if their body are getting that much radiation for the whole year.
TL;DR you're always getting some ionizing radiation, how much matters.
> They had 300 counts per minute which would e around 6200 mSv year
Are you sure about that? 6200 mSv is 6.2 Sv, which I understand to be near-universally deadly. That dosage would be profoundly incompatible with the news that the worker was being sent offsite to seek non-emergency medical attention.
Poking around, it looks like "counts per minute" have to get converted to a dosage using an instrument-specific formula. I CBA to go find that formula, but you're quite welcome to.
Rate matters. 6.2Sv in a single hour is fatal. 6.2Sv in a single year is probably less than average for a human from background radiation. The measurement units for ionizing radiation are very complicated and confusing. That's why people are told to not try to compute this stuff yourself. I have code that computes these units and conversions, its not simple. Here is a brief and simplified explanation of how you calculate this stuff.
There are 4 types of ionizing radiation: alpha, beta, gamma/x-rays and neutron flux. Each one has a different rate it is blocked by different materials (water, air, etc). Each one has a different risk to people. You have to compute counts per unit time emitted from a point source for each of the different types of radiation. Then you have to compute the amount of "arc" the person is in. Then you have counts being absorbed and you next multiply each count by a fixed factor depending on the type of radiation. This final number gives you total Greys per unit time, then you then have to divide by the mass of the person. Then you multiple that number by the total amount of time and that gives you total Greys absorbed. That's the number you use to assess risk to the person. For reference, this guy probably got less than 1 Grey. Someone getting radiation treatment for cancer might get 75 Greys.
So please stop trying to calculate this stuff yourself. I'm pretty sure you are doing it wrong. This guy will be fine.
PS Sieverts are a physical measure, Greys are a measure of biological "harm".
> PS Sieverts are a physical measure, Greys are a measure of biological "harm".
The US's NRC disagrees with you. From [0], they say this about the sievert and rem:
Dose equivalent
A measure of the biological damage to living tissue as a result of radiation exposure. Also known as the " biological dose," the dose equivalent is calculated as the product of absorbed dose in tissue multiplied by a quality factor and then sometimes multiplied by other necessary modifying factors at the location of interest. The dose equivalent is expressed numerically in rems or sieverts (Sv) (see 10 CFR 20.1003). For additional information, see Doses in Our Daily Lives and Measuring Radiation.
and have this to say about the gray:
Dose, absorbed
The amount of energy absorbed by an object or person per unit mass. Known as the “absorbed dose,” this reflects the amount of energy that ionizing radiation sources deposit in materials through which they pass, and is measured in units of radiation-absorbed dose (rad). The related international system unit is the gray (Gy), where 1 Gy is equivalent to 100 rad. For additional information, see Doses in Our Daily Lives and Measuring Radiation.
Grays seem to be "amount of radiation absorbed per kg". Looking further, the "Measuring Radiation" page at [1] directly contradicts your claim. Speaking about rems and Svs, it says:
Dose equivalent (or effective dose) combines the amount of radiation absorbed and the medical effects of that type of radiation. For beta and gamma radiation, the dose equivalent is the same as the absorbed dose. By contrast, the dose equivalent is larger than the absorbed dose for alpha and neutron radiation, because these types of radiation are more damaging to the human body.
I'm definitely not an expert, but the NRC is pretty official, and their explanations sound pretty clear to me. Is what they're saying here incorrect?
> 6.2Sv in a single year is probably less than average for a human from background radiation.
Are you sure about that? <https://xkcd.com/radiation/> claims 4 mSv per year as normal radiation dosage, and 50 mSv per year as maximum permitted annual dosage for "US radiation workers", whatever that means.
I think you're off by a factor of a thousand for the typical exposure level and off by a factor of a hundred for the exposure level where they stop letting you work near the radioactives for a year.
No, you are just confused about the technical jargon being used. That text is written for people who have had this jargon hammered into them and is very confusing to people who haven't. This is why people are told to not try to do the calculations themselves.
"Dose absorbed" is a physical measure of ionizing radiation that is directed at something. That's measured in rems or sieverts (or Grays, notice the spelling). "Dose equivalent" is a medical measure of the risk caused by that "Dose absorbed". That's measured in Greys (with an E, not an A). Both those measures combine the count rates for the 4 different types of radiation into 1 amount. "Dose equivalent" goes farther and is meant to calculate medical risk to a living person. Even more confusing there is a Gray (dose absorbed) and a Grey (biological impact of a dose absorbed, or dose equivalent); they are different.
The part about beta and gamma radiation is about establishing a baseline for converting between the two units but should never be used for calculating "dose equivalent" in practice. Its how we determine the value of 1 Grey. It isn't a way to convert from "dose equivalent" to "dose absorbed".
I'm trying to simplify this stuff for an audience without the necessary background information. Doing that requires me cutting out a bunch of details. The NRC text on the other hand is technically precise but also is mentioning a lot of things that are true but confusing or only useful for calibrating instruments. They are also explaining one tiny part of this and you left out the parts where they talk about how to combine the different counts for each type of radiation into one measurement. That's something else I'm also trying to explain at the same time. So I'm covering more ground and trying to do so with simpler terms. That's going to mean you can cherry pick stuff but doing that will to give you the wrong impression.
Natural background radiation varies by location on earth by a factor of 300. That 4 mSv per year is for natural background radiation at the low end of the scale which happens at sea level in places without Uranium or Thorium deposits. However, there are places where people live (and have lived for 1000s of years) where the natural background radiation is 300x that amount or about 1.2Sv/year. There is no observed increase in cancer rates in those locations despite decades of study. I'm also assuming that the "normal person" will take a flight or two and potentially be near other sources of radiation without knowing it (like your smoke detector).
PS The 50 mSv/year number is absurdly low. Its one of the main complaints about how the NRC handles nuclear radiation. Its literally lower than the natural background radiation at sites in India and Brazil.
> Dose equivalent" is a medical measure of the risk caused by that "Dose absorbed". That's measured in Greys (with an E, not an A).
Neither the NRC nor the EPA nor the NIH nor the NRC seems to know about the "Grey". Everyone in the US seems to know about the "Gray" (abbreviated as "Gy"), which is used to measure dose and doesn't factor in biological harm.
What country uses the "Grey" unit? What's the abbreviation of the "Grey" unit? Would you point to credible sources for the answers to those two questions?
> "Dose equivalent" goes farther and is meant to calculate medical risk to a living person.
Yes. That's biological harm. Getting hit on the skin from outside your body with a large amount of alpha radiation is far less harmful than getting hit with the same amount of gamma radiation. AFAICT, "dose equivalent" is measured in Sv or rems.
If you can demonstrate a credible source for the "Grey" unit, then I can dismiss this as a time-wasting misunderstanding, but I've yet to see any reference to a "Grey" unit of radiation exposure.
> Its literally lower than the natural background radiation [at some places on earth]...
Yep. ALARA is a scourge. And I -too- have read Admiral Whatshisface's open letter from the 1980's or 1990's or whenever about how the regulation of the civilian nuclear energy program is batshit nuts by way of being negligently overcautious.
no not sure. yeah I used the an average instrument specific rate. The point is a) everything emits, b) we have no idea on severity from the info, could be a little, could be a lot. Could also be short term (haircut) or longer term (ingested) exposures.
> yeah I used the an average instrument specific rate.
Would you provide a link to the source of this average instrument specific rate?
I'm interested in knowing which instruments designed to detect low-to-medium-level radiation sources on a human are configured so that five detections per second would equate to a "You're fucking dead; there's really no hope for you" dose.
(Did you ask an LLM to "convert counts per minute to mSv" and fail to sanity-check the confident-sounding result it gave you?)
> ...everything emits...
Given that the crust and sea and air of this planet are chock full of radioactives, and that every living thing on the planet builds itself out of that material, that goes without saying.
You need a device that can measure the different types of radiation. Then you have to do a bunch of calculations to estimate absorption. Only then can you calculate Greys which is the measurement that matters.
PS 300 CPM is nothing. There are places where people live where the natural background radiation is higher than that. Also, background radiation is mostly Gamma rays which is more dangerous than what comes off of fission products or nuclear fuel.
That depends on the instrument. It's an instrument-specific rate. I'd say that saying "300 CPM is nothing" absent any information other than the CPM is foolish.
As I indicated earlier, given all of the other context we have, we can reasonably suppose that 300 CPM from whichever instrument was used in this incident is nothing to be concerned about.
Hair can't hold that much water compared to any ingested amount. Whether contaminated or activated, internal irradiation from that much will be pretty bad.
