What is Nuclear Waste and How Will It Kill Me?
Editor's Note: Hey, it's Uday, I'm also the editor because I don't have the money to hire an editor. I recently wrote a piece "Why is Nuclear Power Not in the Green New Deal?" which presents nuclear power as an economically and environmentally viable solution to the energy crisis and climate change. To help people understand the subtleties of nuclear power, I'm launching a set of companion pieces in a series I'm calling "How Will It Kill Me?" Previously, we talked about radiation Today, we tackle nuclear waste.
In any discussion about nuclear power, the vast number of benefits are seemingly always overshadowed by one deal-breaking deficiency: where, oh where shall we put the waste? Partially due to the portrayal of nuclear waste in pop culture – either as an initiating event for a tragic family death or a means by which to gain superpowers – it has become a symbol for the post-nuclear hell-scape, yellow cans with the dreaded trefoil oozing green goo from the crevasse between the fractured lid and degraded body.
The importance (and danger) of nuclear waste is indeed the most legitimate criticism that nuclear power faces, especially when we eventually (hopefully?) reach a 100% nuclear world. But these concerns are exacerbated by a depressing medley of ignorance and misinformation. Let's take this chance to educate ourselves about what the waste is made up of, how bad it is, how long it stays around, and where can we put it turning ourselves into the next iteration of the Avengers.
A quick caveat – Yes, there will be science here. There are a lot of scientific-sounding terms and concepts without which it is impossible to talk about radiation in a meaningful way. If you make it to the end, there's a fun rant as a reward.
Basics first, coach. What is actually in nuclear waste?
There are three main kinds of nuclear waste, aptly named low, intermediate, and high-level waste. The main thing when it comes to volume is the low-level waste – this accounts for around 90% of all waste generated from nuclear activities. As the name might suggest, the amount of radioactivity involved here is low. Even though there is so much of it, it only accounts for 1% of the total radioactivity of nuclear waste. Most low-level waste is just generic lab trash, things like gloves, wipes, and tools.
You might wonder why it's even designated as nuclear waste if it's barely radioactive. This is more of a regulatory definition – low-level waste is defined as all nuclear waste that doesn't fall into the categories of high or intermediate-level waste. So there's no specific definition of what low-level waste is, just what it's not. And 'nuclear waste' is pretty much anything that's come into contact with radioactive material. For example, if you work in a laboratory (not at a power plant, just at a laboratory) where radioactive materials are located, any gloves that you use can automatically be designated as nuclear waste, even if you didn't use those gloves to actually handle the radioactive material in the room. That's why there ends up being so much of it – it doesn't even matter how radioactive it is. You could point a detector at it and get absolutely no gamma radiation (above background levels), but because of how the waste was created, it is treated as nuclear waste anyway. You might even call this more 'politically radioactive' than actually radioactive – a prime example of the need for smarter regulation.
Intermediate-level waste is probably the most unremarkable type – it's both negligible in terms of volume (7% of all waste) and radioactivity (4%). This type of waste comes from very specific types of processes, like the production of radioactive isotopes for medical use.
Back up, you skipped over high-level waste.
Yeah, you caught me. While low and intermediate-level waste is of very little concern, high-level waste is the stuff that does need to be taken seriously. It's responsible for the vast amount of the radioactivity of all nuclear waste (around 95%), but there's very little of it by volume (just 3%). You can think of this kind of like Bernie Sanders' catchphrase about the economy – the top one-tenth of one percent (the high level waste) have as much wealth (radioactivity) as the bottom ninety percent. High-level waste is mainly the leftover stuff from inside a nuclear reactor after fission has occurred, which is called Spent Nuclear Fuel. So, what exactly do we get from fission?
Remember, a fission reaction involves breaking apart an atom of your fuel of choice, usually Plutonium, Uranium, Thorium, or some combination thereof. One of the interesting things about fission is that you always get the same number of products, but the actual identities of the products differ. You know of course that the masses of your products have to add up for the math to work out – for example, if it's Uranium-235 that's being broken apart (fissioned), the products have to add up to a mass of 235 – but that leaves you with a bunch of possible combinations. Experimentally, we get the following trend, which shows how often certain elements show up following fission.
A few observations can be made – it doesn't seem to matter what kind of fuel you use (the curves all overlap significantly), and there seem to be two 'humps'. Intuitively, you'd expect something that breaks to break in half (e.g. Uranium-235 breaking into two things with an equal mass of 117.5 each), but that's not what this shows. Typically, we get one lighter element (from the left hump) and one heavier element (from the right hump) every time an atom fissions. So if you have millions of atoms fissioning in a reactor, you'll end up with a distribution of elements something like the curve above.
Sometimes, you can actually extract some useful materials from the spent fuel, which can be used again in a reactor to generate energy. This is called Reprocessing, and byproducts of reprocessing are also classified as high-level waste. This is the nuclear version of recycling – there's stuff you definitely can't recycle (like Styrofoam) that has to go to the landfills, but there is stuff (mostly glass, aluminum, and other metals) that you can get another use out of. Reprocessing reduces the total volume of high-level waste that has to be disposed of.
The waste is bad because it's radioactive, right?
Pretty much. It's because of radioactive decay, which results in gamma rays, a form of ionizing radiation (energy) that can cause damage to the human body. If you don’t know / forgot what radioactivity is, read my companion piece here. Remember that radiation from nuclear waste isn't a 'special' kind of radiation. It's all just energy. It's the same thing as the radiation coming from your banana, except waste has more of it.
Quick clarification: Just because something is produced as a result of a nuclear reaction doesn't mean that it's radioactive. Again, nuclear stuff is NOT necessarily radioactive. Fission produces some isotopes that are actually stable, so the waste as a whole has some parts that are radioactive, and some that aren't.
How long do things stay radioactive?
This decay process isn't predictable on an individual basis (I can't tell you when exactly the next decay is going to happen), but is predictable in a probabilistic sense (I can tell you the decay behavior over a long period of time). This is the purpose of a Half-Life – the amount of time it will take for roughly half of the element to decay. Certain isotopes have a half-life of a fraction of a second, while others have half-lives as long as millions of years.
The magic number for 'how long things stick around' is seven half-lives – if you have some amount, and half of it decays away, and then another half, and so on for seven times (1/2 raised to the power of 7), you'll end up with less than 1% of what you originally had.
There is also the matter of what things decay into. Something that's radioactive (a 'parent' isotope) can decay into something else that's radioactive (a 'daughter' isotope), which then itself has to decay (into a 'granddaughter' isotope – I have no idea why these are gendered). This process continues in such a Decay Chain until you get to something that's Stable. A stable isotope is one that doesn't undergo decay: of the 3,339 known isotopes, 253 are considered stable.
Another complication is that things can decay in multiple ways, each of which has its own probability of occurring, resulting in branches of decay chains.
Take a look at the decay chains of our favorite nuclear fuels Th-232 and U-235 to see just how crazy this can get. Uranium-235 (the right one) has a decay chain that is 11 isotopes long. You can see that there are multiple paths; for example, Francium-223 (in red) can decay into Radium-223 (via beta decay) or Astatine-219 (via alpha decay). Uranium-235 itself has a half-life of 700 million years, and everything down the chain is dramatically shorter-lived. All paths eventually take you to Lead-207, which is stable.
Think of radioactive isotopes like different types of caterpillars. Caterpillars (the 'parent') usually exist as caterpillars for weeks to months before cocooning, but only stay in their cocoons (the 'daughter') for a matter of days before emerging as butterflies or moths (two possible 'granddaughters', depending on the type of caterpillar). If you were to walk away from your caterpillar farm for some amount of time and then come back, some number of caterpillars would have transformed (based on their 'half-life' of staying a caterpillar). You'd probably see a lot of caterpillars and a lot of butterflies and moths, but not too many cocoons because the cocoon stage lasts for a relatively insignificant amount of time. And these bugs are fundamentally different: the moths might be harmless (stable), but the butterflies might be vicious (radioactive). Wouldn't nuclear power be so much more appealing if butterflies were radioactive?
Just how radioactive are these butterflies?
Most fission products (again, we're considering only high-level waste and spent fuel) have fairly short half-lives on the order of a few years, so it would only be a matter of decades before their radioactivity becomes negligible. But there are a few long-lived isotopes – ones with half-lives greater than hundreds of thousands of years – that we have to look at. Most of these either do not emit gamma rays (instead emitting beta particles) or emit very weak gamma rays. There are a couple of these that do emit some dangerous gamma rays, and a couple that are dangerous biologically (*not* because of their radioactivity).
So a few of these radioactive butterflies might be immortal.
I think we might have to kill these butterflies.
Fortunately, there is also a (humane) method to deal with these isotopes called Nuclear Transmutation. A few decades ago, this would have been called alchemy – the fabled process that could turn lead into gold. It's actually possible to turn lead into gold with today's technology, but the energy cost of doing so is way more than the value of the miniscule amount of gold you'll end up producing. Transmuting, or changing an isotope is simply done by bombarding it with protons and neutrons. Remember, an isotope is defined by the number of protons and neutrons that it has, so if you add protons or neutrons to the nucleus, you can completely change its identity. Nuclear fission is, in a sense, a transmutation: you're bombarding a fuel (like Uranium-235) with neutrons to make it split apart, this changing its identity. Long-lived isotopes that are also biologically hazardous, like Technetium-99 and Iodine-129, are good candidates for transmutation.
Transmutation, like decay, is probability-based. There are well-established values called Cross-Sections, which are simply probabilities for certain types of reactions occurring when particles of a certain energy hit a certain isotope. For example, we know that if a neutron at a very high energy (say, 1 MeV) is shot at a Uranium-235 nucleus, it has a very high probability of just bouncing off and giving up some of its energy, a solid probability of creating heat as a part of that collision, and a low probability of being captured and thus causing fission. We can also see that as the energy of the neutron is decreased, the probability of fission increases substantially.
These kinds of plots exist for every single isotope, every kind of reaction, and every energy. So, we know which isotopes would be eligible for transmutation, because they need to have an appreciable capture cross-section (probability), and one that's higher than the cross-sections for other types of reactions (like bouncing off). Transmutation is still a developing field, and it's not a catch-all solution. Transmutation would not serve to dramatically decrease the overall quantity of waste, but rather mitigate the threat level of said waste. Instead of having biologically hazardous waste for millions of years, it's brought down to a manageable time period of a few thousand.
So if you shoot your radioactive butterflies with a stream of nectar, there's a chance that they'll turn into harmless moths. Or something. I think this analogy has run its course.
This is all theory. Practically, how long should we worry about waste?
The theory does hold up in real life. All products considered, high-level waste needs to be stored for a few decades in a pool-like containment, by which time the radioactivity has decayed down to not-super-dangerous level. Then, it would move to a semi-permanent storage for around 10,000 years. At that point, enough decay has occurred that the waste is about as radioactive as stuff that's in the ground. So if you wanted to, you could take waste out of containment after 10,000 years and have it for lunch. Maybe the human palette will have evolved by then.
Yeah that's enough science. Where do we put it?!
Underground. Yeah, it doesn't sound like a sophisticated solution, but it's certainly a functional and sufficient one. Remember that radiation is only harmful if it gets to you, and the best way to lessen that amount is to put a lot of distance and shielding between you and the source. These Deep Geological Repositories are a few hundred feet below the surface of the Earth.
As discussed in the original piece, we actually have evidence that this kind of an approach would work. Obviously we haven't been generating nuclear waste for 10,000 years, but 2 million years ago, there was a 'natural' nuclear reactor – a place in the Gabonese Republic which had the perfect conditions for fission to occur. This natural reactor naturally produced nuclear waste (the remnants of fission), which is a useful case study of how nuclear waste will move if left undisturbed. Turns out the waste – which is estimated to be several tons – didn't really move all that much. And that was without intentional confinement or security.
Do we have enough space for all the waste?
Absolutely. Right now, nuclear powers about 11% of the entire world, and produces about a million cubic feet of high-level waste. That might sound like a lot, but a football stadium (increasingly a standard American unit of measure) is around 100 million cubic feet. So if we're operating at 100%, you can anticipate that we'd be producing a radioactive football stadium every ten years. And while a stadium is big, we have billions of acres of usable land on Earth available to be transformed into deep repositories.
Let's extrapolate this out over time – let's say you need a single football stadium per decade, and the waste has to be kept there for 10,000 years. You'd need a total of 1,000 stadiums' worth of space, such that in year 1,001, you can remove year 1's waste since it is no longer considerably radioactive. Again, still manageable.
The amount of waste you get is small because the amount of fuel you need is small, at least compared to other sources of power. Remember that this is the high-level waste: the really bad stuff that is 3% of all nuclear waste by volume. If you also want to consider low-level and intermediate-level waste, you'd get a total of 4 football stadiums of waste per year. But remember that nuclear-friendly regulations (e.g. the ability to dispose of something with no trace of radioactivity as municipal waste), regulations which would presumably exist in a world accepting enough to be fully nuclear-powered, can cut this volume down dramatically.
You promised me a rant. Now's the time.
All waste is dangerous in some way, right? Plastic is dangerous because it can be harmful to ocean life. Paper is dangerous because, uh, it can give you a papercut when you're taking out the trash. And when you're talking about power generation, there will always be some waste, a subset of which has the capability to cause tangible harm. It's an inescapable con, the existence of which you will have to convince yourself is worth it.
Yet, the problem of waste is always treated as something that uniquely belongs to nuclear power, which is the most consistently frustrating aspect of discussing nuclear policy. Waste from existing and established power sources is never used as a point of reference; rather, nuclear is held to a higher standard as the new kid on the block. We demand answers from nuclear power to questions that we never routinely ask about anything else. And though nuclear power answers those questions emphatically by actually taking responsibility for disposing of its waste in a responsible manner, it is subject to an excessive level of scrutiny and ire. A simple report of a radioactive material spill will draw protests and increased regulation in a heartbeat, but the routine pollution of our air and water is tolerated as a simple cost of doing business.
Drilling into the ground requires the use of a fracking fluid that contains hundreds of chemicals including the likes of Hydrochloric acid – a fluid that can easily get into groundwater. Fly ash and liquid waste from coal mining has things like Arsenic, Beryllium, and Mercury – all bad things which all leach out into the surrounding environment. In a best-case scenario, the EPA determined that a coal landfills could leak several gallons daily! This is the best care scenario!
Oh, and coal mining and natural gas drilling also results in *nuclear* waste. Yeah, that's right, nuclear waste doesn't just come from nuclear power generation. You know how there is naturally-occurring radioactive material sitting in the ground, like Uranium and Thorium? Turns out, when you try to dig up coal or frack up the ground, you'll also inevitably end up digging up things that are radioactive as well. And this stuff isn't disposed of properly in drums and kept deep underground. This is all surface-level waste in the form of powders or ash – mediums that make the radioactivity highly dispersible. Pound-for-pound, a coal plant can carry a hundred times as much radiation into its surrounding areas than a nuclear plant, because a nuclear plant has proper, safe methods for disposing of its relatively small volume of waste. This double standard is literally written into the law – the acceptable level of radioactivity for waste coming from nuclear activities is a thousand times lower than for waste from any other source, including waste generated from coal and oil-based power.
And that's all without mentioning the worst waste product… greenhouse gases! Yeah, remember those? Carbon Dioxide and Methane? The whole reason that we should be trying this nuclear thing in the first place? Even if you think that nuclear waste may be a problem eons from now, catastrophes should be dealt with in the order in which they are trying to destroy us. Global warming can be directly traced to greenhouse gas emissions into the atmosphere – let's make sure that humanity is around to witness the prophesized nuclear wasteland.
Give me a numbered list. Please! You did it last time.
Ugh, fine. You deserve it. Say the following ten things as a prayer before you go to bed every night.
1. There's low-level, intermediate-level, and high-level nuclear waste.
2. The high-level waste, which is mostly spent nuclear fuel, is responsible for almost all of the radioactivity but is very small in quantity.
3. Spent fuel is made up of fission products, some of which are more common than others.
4. Many of these fission products are radioactive. They will decay at a speed governed by their half-life, and can decay in different ways (alpha, beta).
5. Decays will keep going in a decay chain until you get to an isotope that's stable.
6. There are some very long-lived fission products that can undergo nuclear transmutation to turn into something that's not quite as long-lived.
7. We probably have to worry about nuclear waste for around 10,000 years.
8. Currently at 11% capacity, nuclear power generation produces one football stadium's worth of high-level waste every ten years.
9. Nuclear waste is actually created as a byproduct of other methods of power generation as well.
10. Nuclear waste is, both fiscally and environmentally, much less costly and burdensome than the collective effects of the likes of coal and natural gas. Like way less. Unbelievably less.
*Note: The primary purpose of this piece is to communicate qualitative themes about nuclear power, and hence intentionally does not cite the sources for the statistics presented. Readers are encouraged to research these important topics, particularly in peer-reviewed scientific journals, for confirmation.