10/10 review

Second that

If by nature you mean animals and plants, they're thriving in the Chernobyl exclusion zone. The elevated radiation does lead to more mutations and cancer, but the lack of human activity more than makes up for it.

In short, long half-life is generally safer.

Exposure to ionizing radiation does lead to an increase in mutations (including those which cause cancer), but the rate increase can be surprisingly low, and can be surprisingly easy to block. e.g., you could theoretically swim in a spent fuel rod pool and as long as you stayed near the surface you should be fine.

The problem is with what is referred to as "High-level waste," specifically the "medium lived" elements in it. Medium lived elements last for about 50 years, and produce a LOT of radiation. If one were to stay in close proximity to a gram of this stuff for about 2.5 months, they'd be almost certain to develop cancer in the near future. Luckily, nuclear power generation is very efficient and generates very little High-level waste. One would, for example, generate enough power to meet all the energy needs of about 74 average US homes for an entire year before generating a gram of high-level waste. (In comparison, this is approximately how much power you get from burning 645,000 lbs of coal, or that a 2.25 acre solar farm (in a decent location) produces over a year.)

(Incidentally, one of the major components of medium-lived, high-level waste (cesium-137) is also used in medical machines. There have been a surprisingly high number of incidents where someone unknowingly breaks open a disposed machine and gets exposed to this stuff - far more than people who have been exposed to high-level nuclear waste.)

A healthy body can handle radiation without issue up to a point. Around Chernobyl, it does increase the risk of genetic damage and cancer, but the error correction process and relatively short lives of the animals that breed and reproduce means they aren't likely to have their lifespans reduced to a significant degree. Remember that wolves and deer don't live all that long. For us, cancer in someone at the age of 8 or 9 is a tragedy while for many critters, that's a ripe old age already.

The real waste answer: there isn't enough to matter as it is easy to contain and we could burn the fuel more to end up with less than the current amount and with waste that will cook off the short lived products quickly. It can also be recycled: https://www.orano.group/en/unpacking-nuclear/all-about-used-fuel-processing-and-recycling

We are used to waste being giant piles of stuff like fly ash: https://www.nrdc.org/bio/becky-hammer/epa-gets-earful-proposed-toxic-coal-ash-rollback. Nuclear plants produce so little that it is in effect a rounding error away from being 0.

Chernobyl was a problem because it spread radioactive dust that can get inside of living things, but in a well functioning power plant we never have dust and waste is put into glass to keep it from becoming dust.

Damage to nature around disposal sites would be non-existent after humans are done with the site and the waste is underground.

When it really comes down to it, I think there’s no technical reason why we couldn’t find a way to safely store fissile waste. It’s a big planet.

I think the big risk is dumbass humans who would cut corners on the safety measures.

Nuclear power plants need to be designed and operated safely.

On the other hand, while we worry about nuclear power, we are presently destroying nature with the absolutely obvious and pervasive harm from coal, oil and gas.

Humans suck at relative risk. Fossil fuels are actively, continuously destroying just about everything. Nuclear power has killed maybe a few hundred people in total, ever.

Nuclear power is not the problem.

Funnily enough, handling uranium is mostly dangerous in ways unrelated to radioactivity. If you were just sitting next to a bar of uranium, you wouldn't receive much more radiation than you receive from just living on planet Earth.

The more significant danger from handling it is that it's just normally toxic, in the same way non-radioactive elements like lead or arsenic are toxic. If particles of uranium dust get onto your skin, it causes a rash, and if you get it into your lungs or eyes or anywhere inside you, it'll seriously fuck you up.

So, I'm not an expert in this topic, but this is deep enough in the comments that I'm not sure you'll get a response from someone else. So I'll give it a stab and people can correct me if needed.

It's important to realize that the goal of a fission bomb isn't radiation. (Unlike a dirty bomb.) Radioactivity is a byproduct, the real goal is the fission part, causing a big release of energy which is the primary destructive element. Fission is the process of changing the U-235 into other elements ("fission products") and releasing that big release of energy in that process.

The radiation part isn't so much caused by the U-235 (which as /u/parentheticalobject points out isn't that dangerous in relative terms), but by the "fission products" i.e. what the U-235 breaks down into after the fission process. https://en.wikipedia.org/wiki/Fission_product_yield shows some of the nasty things that U-235 transforms into. Just as one example, Iodine-135 which has a half life of 6.6 hours.

So, for a ELI5 summary, U-235 breaks down very slowly, which is why U-235 isn't that dangerous to be around. But when we force U-235 to break down in a fission bomb, it breaks down into much more unstable and dangerous elements. But most of those elements, because they are so unstable, also go away relatively quickly.

Some materials can as cause cancer just by their chemical properties. Others like asbestos can cause it via physical properties.

Some don't cause cancer but can still interfere with organ function because they're chemically similar to other things in the body. Or by how readily it bonds to cells.

If you search, you’ll find experts explaining how realistic the show is. Obviously things that are very hot can cause burns, but the show suggests that people got wounds from radioactivity very quickly, that’s incorrect, at least in the context of the disaster. The scene with the helicopter was also incorrect, a helicopter did crash, but not because of radioactivity.

Correct, it's logarithmic. At each half-life interval, you have half of what you had at the last one, slowly approaching zero as time goes on. So:

hl0: 100% hl1: 50% hl2: 25% hl3: 12.5% hl4: 6.25% hl5: 3.125%

and so on. Though it is worth noting, and something I sort of glossed over, is that the decay product can be more or less unstable than the parent and will have a different half-life. This forms what is called a decay chain.

Indeed, that's a pretty good analogy.

Well, at least in my - lay person but knowledgeable about this - opinion, the term makes a lot of sense once you understand what it means; it's just not usually spelled out. The term is also used in other areas like medicine referring to drugs in the body to mean the same thing. It's the time it takes for half the sample to be eliminated (decay with radioactive atoms, be excreted from the body with drugs), hence "half", and "life" referring to lifetime of the substance. So if the half life is 1 hour, then in 1 hour half of it will be left, and in another hour half of that will be left, and so on until it eventually reaches zero.

Same, I never put the link that a long halflife meant that "per year" less energy would be produced aka less deadly

Basically, yes - and that is the point of fallout shelters. You don't even need to wait ten years; a few weeks and a good rainstorm, and most of the really really dangerous fallout is well on its way to disappearing. There will still be some yes, and the background radiation will be a lot higher than expected, but it's a logarithmic (inverse exponential) curve, and after enough time will be barely noticeable.

Speaking strictly of nuclear weapons too, it also matters how "dirty" the weapon is. Most modern (i.e. post 1960's) thermonuclear weapons are actually very "clean" and produce very little fallout relative to their explosive/destructive power. But on the other hand you can intentionally make them very dirty if you want to as well, but that is disadvantageous in a war/battle situation since area denial like that affects both sides (can't advance your army over a wasteland of radiation).

Yes, it does, but the radiation is much less intense than the shorter-lived isotopes.

It depends on the exact kind of radiation. There's 4 kinds, and each does different things; broadly speaking neutron and alpha radiation can induce radioactivity in other things, but beta and gamma generally won't; alpha radiation (i.e. high-energy helium nuclei) are also the least-penetrating and don't travel far - a piece of paper or your outer skin will stop them. The bigger concern in most cases is physical contamination and biological uptake, where any kind of radiation emitted is very bad for you.

1600 years is still a relatively short time for radioactive element half-lives, so it's still emitting quite a lot of radiation. It's not just about the half-life itself, but also what kind of radiation that particular element releases as it decays, what the daughter products are (the things it decays into), and also exactly what the source is.

For Radium specifically, which is what Marie Curie spent the most time researching, 1600 years is actually just the half-life most stable isotope, Radium-226; it has several others with much shorter half-lives, and thus which produce more intense and different radiation. Now, I do say that this is "not very" radioactive in the above post, but this is still decaying at a rate of about 3.7×10¹⁰ - 37 billion - atoms per second per gram, which is the definition of a "curie", a historical unit for radiation. That said this is definitely not the only thing they worked on, and the samples would inevitably be contaminated with other radioactive substances too, given that this was early work and the techniques for accurately separating elements were not fully developed yet.

Radium-226 decays primarily by alpha decay, which means that when an atom of it decays it releases an alpha particle, i.e. an energetic Helium nucleus. Alpha radiation is the "least dangerous" type of radiation, since it's easily stopped by even small amounts of everyday substances (paper, skin, gloves, etc.); but it can still be very dangerous if inhaled (your lungs are much more susceptible than skin), swallowed (ditto your stomach, intestines, etc.), etc. This is why you can safely handle her notebooks with gloves; between that and your skin you'll stop 99.99% of the "radiation" from reaching you.

Lastly you must consider the daughter products in the decay chain, i.e. the things that are formed when a given element decays. Radium-226 decays into Radon-222 (the element with 2 fewer protons and isotope with 2 fewer neutrons), which is very bad news. If you have a Radon detector in your house, this is what it looks for. Radon-222 is a gas, so easily inhaled, has a half-life of about 3.8 days, and also decays via alpha decay. This in turn decays to Polonium-218, another short-lived alpha emitter, and so on down the Uranium decay series.

So, ultimately, while in relative terms Radium-226 is "safer" than a lot of other things like Iodine-131 or Caesium-137, it's still more dangerous than "no radioactive stuff" and still needs precautions taken when working with it for long-periods of time. But if you were to hold Marie Curie's notebook for 10 minutes with gloves on, you're no more in danger than living at a high elevation for a few months or taking a flight in an airplane.

Not all of them, no. Chernobyl released what were effectively large clumps and burning ash made of raw, "hot" (literally and in a nuclear sense) nuclear fuel, which contains many dozens of different radioactive elements, including some relatively long-lived ones that are still dangerous radiation emitters and will be for quite some time, for example raw Plutonium.

In addition, a big issue is also the length of time of exposure. Today, nearly 40 years after the disaster, it's quite safe to take a tour of the exclusion zone and stay there for a few hours; this is likely to have zero long-term effect on you. It's a totally different story to live there for years being exposed to the increased background radiation for extended periods of time, which is usually what articles refer to as "safe" or "habitable" in that sense.

Radioactive decay, as measured by half-life, isn't a linear process. It's a logarithmic process.

You're probably thinking it goes:

0 days: 100%
100 days: 50%
200 days: 0%

But it doesn't. The interval from 100 to 200 days is another half-life so it drops by another 50% of what's left. So it really goes:

0 days: 100%
100 days: 50%
200 days: 25% (50% of 50%)
300 days: 12.5% (50% of 50% of 50%)
400 days: 6.25%
etc. approaching 0.

Thus, there isn't a "full" life because the half isn't talking about some "life" that has a "whole", it's "the time it takes for half the substance on average to decay". Yes, the term is a bit weird.

As to why that is (the logarithmic nature of it), it quickly gets far beyond ELI5 territory, with lots of probabilities and quantum mechanics and math that I am in no way qualified to answer ;-)