Why are Hiroshima and Nagasaki safe to live while Marie Curie’s notebook won’t be safe to handle for at least another millennium?
In: Physics
because marie curie was walking around with radioactive materials; the radiation was able to “seep” inside of everything. As her stuff gets old and more fragile it becomes likely that handling her posessions will release microscopic bits of ratioactive material. marie curie’s diary is not super radioactive any more, but does pose a health hazard if precautions are not taken
walking around with bits of radium and polonium in your pocket over a long time is different than the instant blast of a bomb
Her notebook isn’t actually very radioactive, you can safely handle it for long periods of time with minimal risk as long as you wear gloves.
>”We found that potential external doses to those handling the notebook were low; whole-body dose rates being marginally above the background of 0.1µSv/h. Even regular exposure to the notebook is likely to result in annual whole-body doses of less than 10µSv and hand doses of less than 35µSv. To put this in perspective, 10µSv is roughly the dose you would receive on a return flight from the UK to Spain.” ([Source](https://blog.bir.org.uk/2015/09/02/the-radioactive-legacy-of-marie-curie/))
[Radiation dose chart](https://xkcd.com/radiation/) for reference
Hiroshima/Nagasaki also aren’t very radioactive anymore because most of the fallout was dispersed and the nastiest isotopes have decayed, like I-131 which is the major concern in nuclear fallout, but is gone within weeks due to its short half life. Other isotopes are a problem but it takes decades of exposure to them in the low environmental levels to pose any risk. The US and USSR detonated thousands of nuclear weapons during the cold war, Hiroshima and Nagasaki are mildly contaminated in comparison to those test sites and the people that lived downwind.
There are lots of different ways to blow up a nuclear bomb, and each has it’s own, well I guess you could say pros and cons, but it feels weird to think of nuclear weapons in that regard.
In the case of Nagasaki and Hiroshima they detonated the bombs relatively high up in the air above the cities (as opposed on impact with the ground) which meant most of the radioactive material got carried away by the wind and was dispersed widely enough to be concentrated and nasty. Kind of like how you can see the smoke clouds of fireworks just blowing away slowly as opposed to raining back down as ash immediately. The radioactive materials that did fall-out decayed fairly quickly (within a few days/weeks) and the rest dispersed enough to be lost in the natural radioactive background of our daily lives.
Marie Curie’s notebook is essentially coated in radioactive dust and that dust will take hundreds of years to decay.
For what’s worth, her notebooks aren’t actually especially nasty either and could be handled quite safely, and could also be stored a normal container too, but policy is ‘better safe than sorry’.
the material from a nuclear weapon falls out of the sky pretty fast due to mostly being very heavy. a sub-critical (not exploding) piece of uranium or plutonium is actually fairly safe to be around for short periods of time. After the bomb explodes, the spicy rocks not turned into energy “fall out” and flow down stream in a matter of days. the gamma and x-ray radiation was only dangerous with direct exposure, they didn’t radiate objects. If you look up the Demon Core experiments that killed several scientists, it wasn’t until the screwdriver slipped and caused the sub-critical masses to go critical for a fraction of a second that the damage was done. Curie’s possessions have radium in them now, it never fell out and went down stream. the same thing with Chernobyl.
For the most part, the cities were just exposed to intense radiation, which doesn’t necessarily turn things radioactive, at least not in a way that has a long half life. Curie ground up pitchblende to extract the radium in it, and so radium dust was everywhere. Her notebooks were thoroughly contaminated with it over the years, and that radium remains radioactive.
So if we’d taken the radioactive material from the bombs, ground it up and sprayed it all over the towns, they’d probably still be radioactive.
Marie Curie’s notebooks are, for any practical purpose, safe to handle. The amount of radiation you would absorb by reasonably handling them is like 1% of the recommended safety limits for radiation exposure.
The safety precautions are more of a “better safe than sorry” sort of thing. One general rule with radiation exposure is “As Low As Reasonably Practicable”, that is try to do whatever is practical to limit exposure to radiation. An example of this might be when you go and get dental X-rays they give you a lead vest and trigger the X-ray from outside the room. Safety precautions should include mitigating both direct exposure (i.e. in the same environment as the radioactive thing) and contamination (i.e. transfer of radioactive material to new places). The latter runs the risk of internalizing the radioactive material via ingestion or inhalation, where it would have the potential to cause more harm, and should be a serious concern for something like Curie’s notebook.
short answer: the strength of radiation, point source vs area effected, the half-life of the elements in question, and what is considered “safe”.
strength: without being too reductive, in the same way that a floodlight on a pitch is not blinding, but a handtorch to the eyes at short range can be, the absolute greater radioactive output of a nuke has less residual effect after being spread out over a city and allowed to decay for decades, than the highly contaminated notes if you holding them with bear hands.
half life: while the decay of any individual atom is random, the overall rate is pretty predictable. we measure this with “half life”, how long it would take for half the sample to decay. Higher levels of radioactivity, generally lead to shorter decay times (since that’s what radioactivity IS), and the fallout from the nukes was mostly this shorter half-life stuff. while the notebook is contamined by a long half-life isotope, so its pretty stable in its intensity.
“safe”: their are sources of radiation in our everyday lives, even pre-ww2, and their comes a point where the effects of the nukes in terms of radition effectively disappear into the background “noise” of life on earth. We’re not really seeing any statistical differences in illnesses related to radiation between Hiroshima and other parts of japan that were NOT nuked, so its basically as safe as we can detect.
the notebook, however, is still strong enough that special handling procedures are needed to minimise risk. we can still access the notes, its just that if we picked them up and walked around with them in a pocket, it would be *highly* likely we’d get cancer in areas near that pocket.
Hiroshima and Nagasaki were bombed with nuclear weapons using uranium-235 and plutonium-239 as the fissile materials (Little Boy and Fat Man, Hiroshima and Nagasaki respectively).
Radiation is a release of energy, and the goal of these weapons was to release as much of their potential energies as quickly as possible. This means that the vast, vast majority of radiation was released in the initial detonations.
Both bombs were also “air burst” weapons, meaning that they’re designed to explode long before they impact the ground. Something like 90% of the radiation was blown into the atmosphere.
“Half-life” is a measure of how long a radioactive material takes for half of its total quantity to “cool off” as radiation. Uranium-235 has a half-life of 704 million years. Plutonium-239 has a half-life of 24 thousand years. They’re both radioactive, but leeching radiation pretty slowly.
The super dangerous stuff made as a result of the nuclear reaction would have cooked off the majority of itself within days, or even hours. Combined with intentional and organized cleanup/containment, this means that both cities were relatively safe again in a surprisingly short amount of time.
Marie Curie, on the other hand, was a pioneer in radioactive science. She discovered Polonium and Radium, two *extremely* radioactive elements. Polonium-210 has a half life of only 138 days, whereas Radium-226 is sitting at about 1600 years.
Nothing was known about radioactivity at the time – Curie and her husband quite literally coined the term. They didn’t know to take precautions against radiation exposure, or that radiation could leech into other materials. She walked around with radioactive materials in her pocket. She stored them in her desk. She then worked as a radiology technician in WWI, giving unshielded x-rays and further exposing herself.
They (and other scientists of the era) eventually started to figure it out, but by that point it was far, far too late. Marie Curie died of aplastic anaemia, likely the result of the radiation exposure throughout her life damaging her bone marrow. The reason that her stuff is so radioactive is because she was experimenting with *extremely* radioactive elements through her entire career.
Two major factors. Airburst nuclear explosions are designed to cause maximum damage over a wide area, this also means that the ground isn’t covered in small lumps of radioactive material. The other is the half-life of the materials used, Radium is radioactive for thousands of years. https://youtu.be/AaDwk8UCrew
Because radiation is very poorly understand by most people. Not all radiation is created equal. Not all radioactive materials are the same.
In the case of a nuclear bomb, most of the danger comes from the intermediate fallout products created in the explosion. These are dangerous, but the reason they are dangerous is that most of them experience radioactive decay relatively quickly. So if you happen to be close enough to the bomb when it goes off, you will receive a massive dose of radiation. Of course, the people who are affected by this the strongest also tend to become vaporized by the bomb itself, so the number of people who are close enough to be radiated without being close enough to be instantly killed is relatively low.
More dangerous are the fallout products that have a similar radioactive half-life, but that are biologically important elements. Iodine is one such element, and I-131 is created in nuclear explosions. If you happen to be low on iodine when you inhale fallout products, your body my uptake the iodine and incorporate it into your body, constantly dosing you until the iodine is eventually flushed from your body. This is why governments usually give out iodine pills after nuclear incidents – they’re trying to saturate your body’s iodine levels so that you won’t absorb the radioactive iodine.
But the flip side of this is that most of the ionizing fallout products decay into inert materials relatively quickly. Nuclear explosions produce relatively small amounts of really long-lived fallout products, so the radiation from the bombs in 1945 has pretty much all decayed into inert materials. If you’re worried about exposure to radiation, Denver is actually more dangerous than either Hiroshima or Nagasaki.
Marie Curie’s notebooks, on the other hand, are mostly contaminated with radium. The isotopes in her notebook have a half-life of about 1600 years, so they’re essentially as radioactive now as they were when Curie contaminated them.
If you’re just going to see her notebook, there’s very little risk. You get more radiation exposure from a long plane flight than you do her notebook. However, if any of the radium flakes out and gets into your lungs, you’ll be getting constant doses of radiation until the radium is flushed from your body. So there is a level of risk if you’ll be sharing air with the notebook, or if you’ll be exposed to it for a long time.
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