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Relevant xkcd content: https://what-if.xkcd.com/29/
So if I understand this correctly (solely from reading the xkcd), then the person might actually be okay?
I find it highly informative that the required PPE for working in that location is a life jacket so you float in case you fall in, rather than a tether and fall arrest harness so that it's not possible to fall in.
300 CPM is nothing, background levels might be 150.
Does anyone have a sense for how significant of a dose of radiation this person got?
Unfortunately radiation medicine is pretty complicated and the report gives us very little info, presumably mostly because they don't have very much info. It will take some time and effort to establish more.
What we do know is that they measured 300 CPM at the person's hair, which was probably where they expected the highest count due to absorbed water (likely clothing was already stripped at this point). CPM is a tricky unit because it is something like the "raw" value from the instrument, the literal number of counts from the tube, and determining more absolute metrics like activity and dose requires knowing the calibration of the meter. The annoying thing here is that radiation protection professionals will still sometimes just write CPM because for a lot of applications there's only one or a handful of instruments approved and they tend to figure the reader knows which instrument they have. Frustrating. Still, for the common LND7311 tube and Cs137, 300CPM is a little below 1 uSv/hr. That wouldn't equate to any meaningful risk (a common rule of thumb is that a couple mSv is typical annual background exposure). However, for a less sensitive detector, the dose could be much higher (LND7311 is often used in pancake probes for frisking because it is very sensitive and just background is often hundreds of CPM). Someone who knows NRC practices better might know what detector would be used here.
That said the field dose here is really not the concern, committed dose from ingesting the water is. Ingesting radioactive material is extremely dangerous because, depending on the specific isotopes involved, it can persist in the body for a very long time and accumulate in specific organs. Unfortunately it is also difficult to assess. This person will likely go to a hospital with a specialty center equipped with a full body counter, and counts will also be taken on blood samples. These are ways of estimating the amount of radioactive isotopes in the body. In some cases tissue samples of specific organs may be taken.
I believe that the cavity pool water would be "clean" other than induced radioactivity (activation products from being bombarded by radiation). Because water shields so well the pool should not be that "hot" from this process. Most of those products have short half-lives which, on the one hand, means that they deliver a higher dose over a shorter period of time---but also means they will not longer forever and are less likely to be a chronic problem if they are not an acute one.
I suspect this will get some press coverage and we will perhaps learn more about the patient's state.
Another way we can get at this question is by the bureaucracy of the notification. An 8-hour notification as done here is required in relatively minor cases. Usually for a "big deal emergency" a one-hour notification is required. The definition of such an emergency depends on the site emergency plan but I think acute radiation exposure to a worker would generally qualify.
Scrolling up and down the list, just how onerous is this reporting regulation? It seems almost cartoonishly excessive, even for critical safety applications.
Doing it often doesn’t really add to the cost. More reporting is helpful because it explicitly makes it clear even operational issues can have lessons to be learned from. It also keeps the reporting system running and operationally well maintained.
WebPKI does this as well.
(Not exactly same but close)
Worker was wearing a life vest.[2]
[1] https://en.wikipedia.org/wiki/Palisades_Nuclear_Generating_S...
[2] https://www.mlive.com/news/2025/10/michigan-nuclear-plant-wo...
https://what-if.xkcd.com/29/
Earlier quoted context omitted.
Because it's generally speaking, not that dangerous. Water is very good at blocking radiation. That's part of the reason why the pool is filled with it to begin with.
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?
TL;DR you're always getting some ionizing radiation, how much matters.
> Non Emergency I guess in a nuclear reactor there is a lingual shift and the word emergency cant be used for just any old 911 call. Like how Australians apparently call a jellyfish bite "uncomfortable"
Aussie surfer here, the stings typically are uncomfortable. Some of the deadlier ones can be close to painless and only result in itching and result in you dying from respiratory failure 24 hours later. Others are downright painful with even strong opiate based pain killers struggling to cut through the pain.
https://www.reddit.com/media?url=https%3A%2F%2Fexternal-prev...
Earlier quoted context omitted.
Because it's generally speaking, not that dangerous. Water is very good at blocking radiation. That's part of the reason why the pool is filled with it to begin with.
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?
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).
Earlier quoted context omitted.
Because it's generally speaking, not that dangerous. Water is very good at blocking radiation. That's part of the reason why the pool is filled with it to begin with.
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?
