TOOL The Curve of Binding Energy

 The Curve of Binding Energy by John McPhee was a trip down memory lane for me, and my imagination was fired with nuclear space launches and tunnel-digging. When I heard the title, I thought it’s either going to be some airy-fairy poetic God-knows-what or a deep dive into nuclear science. When I saw the actual curve of binding energy on the cover I knew it was the latter. I enjoyed McPhee’s writing, and his storytelling, and I felt that selecting this somewhat obscure but ultimately central and fascinating figure in the nuclear industry, Ted Taylor, was very well done. The amount of reporting work poured into this blew my mind.

The whole time I was reading I was thinking, “Hold the phone, here, fellas, the USA hasn’t done nuclear material reprocessing since my early childhood. Other countries do it, but we don’t. We just keep spent assemblies in the on-site cooling pools. Don’t we…?” This was a conversation I had with many of the adults I grew up with, time and again. This was the reality of my youth, and I chaffed daily at the short-sightedness of non-reprocessing. Upon reading this book, however, I can see the rock and the hard place coming into focus.

I loved his comments about tunneling between New York and San Francisco using shaped nuclear charges, and getting into space, even bringing such conveniences as barber chairs along, using nuclear explosions to lift payloads into space. Take that, Elon Musk! By the way, one syfy book I read using this concept of nuclear explosions to launch and maneuver spacecraft is Footfall by Larry Niven and Jerry Pournelle. The Earth is conquered by extraterrestrial aliens and humanity builds a ship like Ted Taylor describes to launch itself into space and then maneuver to pursue and ultimately defeat the aliens.

I wonder about radioactive contamination in both endeavors. Blasting a tunnel across the USA would be great, but wouldn’t it be contaminated with unfissioned plutonium? Or would the leftover plutonium be successively fissioned by the neutrons of each successive explosion? How bad is the spreading of plutonium (and other reaction products) from space launches? I don’t know the answer. There is the example of how Kodak (for you camera nuts) found that their Pennsylvania factory runs of developing paper were being ruined, i.e., partly exposed during production, on some days but not others. They eventually worked out that it corresponded with nuclear tests in the Southwest, and they got the DoD to notify them when they were testing nuclear bombs so they could adjust their factory schedules accordingly. That airborne nuclear stuff gets around.

My dad always griped about the idea of burying all of the USA’s plutonium at Yucca Flat. “That stuff is worth billions, and we’ve spent decades producing it! We should burn it up in a reactor!” After reading this book, I’m reminded that I’ve always agreed with that idea. Burn it up and be rid of it, or use it to launch space payloads, or dig tunnels.

My friend Linda whom I visited in Colorado  didn’t like the idea of burning up our plutonium stockpiles, and mentioned how she and her friends protested and got a Colorado reactor switched over to coal.

I liked reading about Ted Taylor’s youthful interest in chemistry. I did a lot of chemistry in High School, but at nowhere near his level. In Idaho Falls, a secret government research community, many of our teachers were actual scientists, and since everybody’s parents were scientists and engineers, the standards were pretty high.

Nuclear energy is scary. As the book points out, plutonium can mimic calcium in the body, which is really bad. I think the transuranic elements, the actinide and lanthanide series, are differentiated from the transition metals by how they start filling up their f-shells, and as I understand things, the f-shells do not extend beyond the 6th and 7th-period s-shells, so they don’t act as valence electrons. So these heavy metals can resemble things like sodium and calcium to some biological processes, but they don’t act exactly the same, breaking said processes, or they introduce radiation into the very cells and bloodstream of the body. Heavy metals are chemically weird—they’re not just like iron and gold needing to go on a diet.

Nuclear science and engineering does have a lot of chemistry. For instance, radium, a radioactive solid, decays into radon, an inert (but still inhalable) gas, which is both a nuclear and a chemical change. Things like fission or bombardment by neutrons in a reactor, lab, or explosion change chemical elements into different ones which suddenly have totally new chemical and mechanical properties. And these are often esoteric radioactive isotopes which act just like their well-known natural, non-radioactive siblings, but emit radiation even if, say, they are absorbed into the body. A well-known example is iodine, and is why iodine tablets are a safety precaution, especially for young children, in case of nuclear accidents. Radioactive iodine is a fission product of uranium, but the thyroid gland will happily absorb it just as well as non-radioactive natural iodine. It can’t tell the difference. Ingest a bit of the radioactive stuff, it decays, emitting high-energy electrons (beta radiation or “beta rays”) into your thyroid and Boom! you’ve got thyroid cancer.

People freak out about “high-level” radiation, but what does it mean? In the iodine example, there’s one isotope of iodine that is “stable” (never decays), one which is stable for about 15 million years (has a half-life of 15 million years), and about a half-dozen other isotopes that decay with a half-life between 13 hours and a couple of months. The point is, that if you get a gram of radioactive iodine in your thyroid, in a few days half of it’s going to turn into something that can expose photographic film, cause tissue damage, etc. Outside the body, beta radiation is far less dangerous, but inside, forget about it. The point is that you eat all the radiation from whatever radioactive iodine gets stuck in your thyroid gland in just a few days.

That’s kind of the problem with plutonium. Uranium, by contrast, is comparatively safe, since it has a half-life of 4.5 billion years. Wait, doesn’t that mean it’ll be around, irradiating and killing us, forever, so we have to bury it all in Yucca Flat and leave nifty, menacing statues around it to warn the intelligent cockroaches that evolve and take over the planet after we’re long gone? Not really. Plutonium-244 has a half-life of 81 million years, while all other isotopes (238 through 242) range from 87 years to 24 thousand years.

Back to iodine for a sec. If you have an environment contaminated with radioactive iodine with a half-life of a week, you wait ten weeks (a month and a half) the level of contamination will drop by a factor of a thousand. So yes, it’s dangerous, but it goes away quickly. Uranium is around forever—all the uranium was created when the star that lived before our Sun exploded—but it puts out its radioactive energy very slowly, spread out over hundreds of millions of years. That’s why it’s used to determine the ages of geologic formations, like rocks and mountains and such.

Uranium and plutonium decay in the same way—by emitting alpha particles, which are, fun fact, the same as helium nuclei. The total USA stockpile of plutonium is something like 100 tons.

240 g/mol of plutonium x 1000g/kg = 240 kg x 400 = 100 tons ( 400,000 mols) 

23 liters / mol of helium = about 2 balloons / mol

200,000 mols from half-life decay of plutonium or a 400,000 balloons worth

So if we locked up all our plutonium in a sealed, geologically stable site and collected all the helium that came off of it, every year we’d get enough to fill up about eight party balloons, and it would still be coming off after a million years or so, but less and less. If that helium were created inside somebody, like lungs or bones, from inhaling or eating it, then they would get cancer, all the cancers, right away. So we have to keep that stuff away from people, at least in an edible or breathable form. And it will take millenia for it to go away naturally. But, if we put it into a reactor, and kept reprocessing the fuel, then it would get burned up, turned into other much lighter elements, and many of these, although they might be “highly radioactive” should decay quickly into something harmless. So we can put all of these nuclear materials into stable sites and watch them for millions of years, or we can, maybe, burn them up, destroy them, extracting energy in the process. Don’t shoot them into space. No. Bad idea.

Anyway, if something is “highly radioactive” then it decays quickly. If it’s “stable” or “not very radioactive” (like uranium) then its decay energy is spread out over a long period and it’s pretty harmless (unless it’s actually also chemically poisonous). Plutonium seems to fall somewhere in the middle. It’s artificial, which helps make it uniquely poisonous, it’s radioactive, but in the zone where it doesn’t decay fast enough to all disappear quickly (like americium, or technetium, for example), and yet it’s radioactive enough to be a serious threat to health. Plus you can make bombs out of it. The fact that it’s so poisonous and hard to work with may actually be a feature not a bug in this regard. I really enjoyed the detailed chemical descriptions Ted Taylor gave of how to purify plutonium and uranium in their various forms.

So, burn it all up and get rid of it, and then press on with Green Energy? Burning up all the plutonium as a way of cleaning up the environment? What about other high level waste? I’m not sure what forms this may take, like what kind of crap do they have buried in leaky tanks at Hanford? Solutions containing dissolved radioactive materials? Kind of a nasty prospect. There also seems to be a lot of sets of hazmat gear buried all over the place in the Arco Desert. Can all that stuff be dug up and run through a glassification or plasma torch process, perhaps adding some non-radioactive inert material, and then just use the resulting slag as Interstate highway paving material (maybe even paint it with phosphorus so it would glow at night—I’m kind of joking with that one).

Who knows if this can be done? I was a bit surprised to read that there seems to have been little progress, and still only prototypes in plutonium (fast breeder) reactors. Water-cooled designs really worry me. I can get into that later if you want. Since I was a kid, I always thought it was a miracle something horrible hadn’t happened, and I think most of the adults around me agreed. My dad and his chums were closely involved with the Three Mile Island cleanup. You can’t shut down a nuclear reactor like you can a car, or even a coal-fired plant. Carnot efficiencies, pressurized water? I could go on and on. Then there’s the French stuff like liquid metal and liquid salt (I think this latter is still experimental). Power plants are always next to rivers or other bodies of water. A swimming pool full of liquid sodium? When I think of reactor designs, I see a lot of fallacy of the last move, and “let’s hope this doesn’t all happen at the same time” and “Japanese people all know that earthquakes and tsunamis always happen at the same time so who the fuck installed this thing?” and “a pool of liquid sodium is great, and it gives you nifty failsafe conditions, but what if a lot of water somehow came pouring in, or the whole pool leaked out into a large body of water…like the river or ocean which will always be nearby as a heat sink?” and “Hello? Steam explosions? Water at multiple atmospheres…in pipes?” It’s not unlike why internal combustion engines pollute so much and are so cantankerous—the working fluid is also the fuel, and the lubricants are also present (more or less) in the combustion chamber. Similarly, in a nuclear reactor, the working fluid is also a moderator and a coolant, and as with everything in a nuclear reactor, as we saw at Chernobyl and elsewhere, a sudden state change (like steam bubbles), or the generation of hydrogen, or xenon, or lots of other things, can completely change how it all works. Neutron bombardment leading to activation and degradation/fatigue of the zirconium cladding, the containment vessel, and so forth. In a regular power plant, the fuel burns, dirty or whatever, the water turns to steam and spins the turbine. We like steam. Steam is a great working fluid and we know a lot about it. Burning fuel gets really hot, thousands of degrees, as hot as you want, making for a nice temperature gradient and a nice Carnot cycle. You want nuclear fuel elements to get hot, but they can only get so hot and then they melt, so they can’t heat steam to thousands of degrees, which is inefficient due to various inconvenient thermodynamic laws. You turn a regular plant off, it’s off—you don’t have to wait weeks for the reaction and residual heat to die down. As soon as it cools, you can go inside and work on it—there’s no lethal radiation. In a pressurized water reactor, the steam is almost turning back into water after one, maybe two sets of turbines, while in a conventional plant you can have three: high-temp, medium-temp, and low-temp steam.

The book makes the point that humans are willing to do anything, to take any risk, to get what they want, or need. It also says that nuclear energy has in a sense ceased to be a choice—we have to use it because of our population and how much energy we consume. My friend also got mad when I suggested that people should stop doing things like using clothes dryers—something about how the proletariat should not be saddled with having to change their behavior to fix systemic problems…something like that. But how do we assess which risks we should take? I’m reminded of the South Park episode where British Petroleum decides the profits are worth it to drill in the middle of the Gulf of Mexico even at the risk of awakening Cthulhu…which of course happens. Zombie apocalypse? Attracting hostile extraterrestrials? Nuclear contamination? These all seem like things that are potentially horrible for one thing, and also hard to assess how likely they are for another. But that may be true for most or all engineering or socio-economic projects. Are some bad outcomes too much to risk no matter how unlikely they may seem, or how cool the thing we hope to get? How to answer this?