Falsifiable, Politics, Science

Nuclear Weapons: 2.0 Basic Science

For this to all make sense, we should start with a brief review of atomic theory.

All matter is made up of atoms. Atoms have an outer shell of negatively charged electrons (more accurate descriptions exist, but I’m not going to delve into them; throughout this section I’m going to use simplified models wherever they’ll do the topic justice) and an inner core containing uncharged neutrons and positively charged protons.

The number of protons in an atom determines which element the atom is. All atoms with two protons are helium, all atoms with six protons are carbon, and so on. Much of the time, elements will have the same number of electrons as they have protons, so that the charges cancel each other out. Forms of elements with differing numbers of electrons are called ions. Ionization is a very common phenomenon. You observe it whenever you see lightning or dissolve salt in water.

Neutrons aren’t as simple; there’s no 1:1 correspondence or linear ratio between the number of neutrons in an atom and the number of protons. Even more confusingly, any sufficiently large sample of most elements will contain atoms that have a different number of neutrons than is most commonly observed.

More concretely, while hydrogen atoms normally have no neutrons, they sometimes have one or two neutrons. Hydrogen with one neutron is commonly called deuterium; hydrogen with two neutrons is commonly called tritium. These unique names bely the fact that regardless of the number of neutrons, the elemental classification of the atom is hydrogen; in almost all cases, the atoms behave identically, regardless of number of neutrons. A deuterium atom, hydrogen atom, and oxygen atom could come together to form what would essentially be water. In fact, you drink water in this configuration every single day!

Different forms of an element separated by the number of neutrons are called isotopes. Normally, chemists assume that isotopes will be in their naturally occurring proportions, which are heavily biased towards stable isotopes. If a specific isotope is being referred to, then it will be referenced with the name of the element and the total number of protons and neutrons; for example, uranium-235.

Isotopes are broken up into two categories: stable isotopes and unstable isotopes. Stable isotopes are at a fundamental resting state. If not acted upon by external forces, they will never change form (to a reasonable first approximation). Unstable isotopes are not at this fundamental ground state and will eventually return to it. The process of returning to the ground state radiates energy. For this reason, unstable isotopes are also sometimes called radioisotopes.

Unstable isotopes also have a characteristic half-life – the amount of time necessary for half of the element to break down into other elements through decay. Elements with a shorter half-life are more unstable, emit more radiation each second, and break down more quickly. Elements with a longer half-life are more stable, emit less radiation each second, but also persist much longer.

The energy released when an unstable isotope reverts to the ground state is commonly termed radiation – the same radiation produced by nuclear weapons, nuclear reactors, and nuclear waste. It mainly comes in four flavours: α-particles, β-particles, γ-rays, and free neutrons.

α-particles are high energy helium nuclei. Because they have a relatively high mass, they tend not to travel far and are unable to penetrate obstacles. A single sheet of paper can stop anα-particle – but their danger shouldn’t be underestimated. An unstable isotope of polonium that decayed and producedα-particles was used in the murder of Alexander Litvinenko.

β-particles are high energy electrons. Since they have less mass and interact less with matter, they can travel much further than α-particles. It takes a few millimetres of aluminum to stop a β-particle.

γ-rays are what many people think of when they think of radiation.γ-rays are photons, the same as radio waves, microwaves, and light. γ-rays have much more energy than more innocuous photons, which causes them to have much smaller wavelengths. Here’s a good rule of thumb about photons: they interact with and can be intercepted by things about the size of their wavelength. TV antennas give you a clue as to the size of radio waves, the mesh or your microwave the size of microwaves, and the tiny rods and cones in your eyes are sized just right for visible light.

γ-rays are much smaller than visible light – they’re sized just right for electrons. This means that they can travel very far, as electrons are very small and any individualγ-ray is unlikely to hit one. Once a γ-ray does hit an electron, it will transfer most of its energy to it, ionizing the atom. This can be very dangerous to humans, killing cells if enough ions are created in them and damaging DNA even when the cells survive. To block out γ-rays, you need to put a lot of electrons between you and them. Four metres of water, two metres of concrete, or 30 centimetres of lead will do the trick.

Breakdown by ejecting free neutrons is comparatively rare. It generally only occurs in significant amounts in the isotopes uranium-235 and plutonium-239.

Any ejected neutron will eventually hit another atom. When it collides, it can cause the atom to immediately fission, releasing more neutrons or be captured by the atom. Whether capture or fission occurs depends on the energy (read: speed) of the neutron. If the neutron is moving at the correct speed, fission will occur. Otherwise the neutron will be captured or bounce off. If a stable isotope captures a neutron, the result is almost always an unstable isotope. Therefore, neutron radiation is the only kind of radiation that can make other substances radioactive.

The observable characteristics of a fission reaction depend on how many neutrons are released (on average) in each collision and subsequent breakup or absorption; none will be immediately released in an absorption, but multiple can be released in a breakup, giving a wide range of possible average values. In nuclear power plants, on average only one neutron is created by each emitted neutron. This causes a slow and steady “burn” of the uranium or plutonium fuel, producing heat that can be harnessed for power. As long as each neutron produces at least one more neutron, the result is a nuclear chain reaction.

In nuclear fission weapons, each emitted neutron generates multiple new neutrons. This quickly leads to a large proportion of the fuel being consumed and turned into absolutely colossal amounts of energy. The smallest tactical nuclear weapons are equivalent to the detonation of dozens of tonnes of TNT, the largest equivalent to the detonation of millions of tonnes. This is where phrases like kilotons (kt – equivalent to 1,000 tonnes of TNT) or megatons (Mt – equivalent to 1,000,000 tonnes of TNT) come from.

The mass at which this out of control reaction takes place is called critical mass. Beyond the critical mass, the reaction is supercritical. Critical mass varies with purity (how great a percentage of the isotopes are the fissionable ones) and shape. A sphere is the shape with the lowest critical mass. This is because in a sphere, the greatest percentage of emitted neutrons are emitted back into the bulk of material – a sphere minimizes the surface area for any given volume. The critical mass of plutonium-239 is 11kg (equivalent to a 10cm sphere), while uranium-235 has a critical mass of 56kg (equivalent to a 17cm sphere).

Criticality can occur with smaller amounts of isotopes than the critical mass in certain cases. Critical mass is tied to density. If you increase the density, you decrease the critical mass by making collisions more likely. You can also lower the critical mass by employing a tamper, a layer around the core that reflects escaping neutrons back towards it, or a moderator (like water) that reduces the speed of the fastest neutrons to one more optimal for sparking further fission.

There is one other type of nuclear weapon. Fusion weapons push atomic nuclei together to form new, heavier nuclei. Fission/fusion weapons aren’t an either/or proposition though. Many nuclear weapon designs incorporate multiple stages. For example, some designs will use the energy from fission to start a fusion reaction and get most of their power from this. Other designs make use of a small amount of fusion to release extra neutrons, which allows more of their fuel to be consumed.

Additional Reading: Proton, Neutron, Radioactive Decay, Nuclear Chain Reaction, Electromagnetic Radiation, and Isotope

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Falsifiable, Politics, Science

Nuclear Weapons: 1.0 Introduction

With President Trump in possession of the nuclear launch codes, I have a feeling that many people who’ve neglected nuclear weapons as an important cause area may begin to sit up and take notice. This is a good thing. There currently exist basically no checks and balances on a US President’s ability to go to nuclear war. Harold Hering was cashiered from the Air Force in 1973 after asking (on the subject of nuclear weapons launch) “How can I know that an order I receive to launch my missiles came from a sane president?”. Nothing has changed since then.

This post series is meant as a non-exhaustive primer on the (declassified) physical and strategic realities of nuclear weapons. It’s supposed to get you up to the point where you can begin asking the right questions in a relatively short time period. If you want more information, I’ve included relevant links (mainly to Wikipedia) at the end of every section. The quality of Wikipedia does vary when it comes to nuclear weapons, so take what it says with some salt.

One final caution: everything in this post series could be obsolete and we would have no real way of knowing. Nations reserve their highest level of classification for their nuclear capabilities and plans. Some of these plans and capabilities can be inferred from what we know of the physics of nuclear weapons or by looking for equilibriums between decision makers, but a lot is hidden from public view.

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Main Series

1.0 Introduction
2.0 Basic Science
3.0 Proliferation
    3.1 Uranium
    3.2 Plutonium
    3.3 Next Steps
4.0 Nuclear Weapon Design
    4.1 Gun Assembly Design
    4.2 Implosion Design
    4.3 Miniaturizing Weapons
    4.4 Boosted Weapons
    4.5 Alarm Clock/Sloika
    4.6 Teller-Ulam Design
5.0 Nuclear Weapon Effects
    5.1 Scaling
    5.2 Direct Effects
        5.2.1 Fireball
        5.2.2 Shockwave
        5.2.3 Direct Radiation
    5.3 Indirect Effects
6.0 Nuclear Delivery Mechanisms
    6.1 Bombers
    6.2 ICMBs
    6.3 Submarine Launched Ballistic Missiles
7.0 Nuclear Weapon Strategy
    7.1 Tactical and Strategic Weapons
    7.2 First Strike, Second Strike, Counterforce, Countervalue
    7.3 Mutually Assured Destruction
    7.4 The Nuclear Triad
    7.5 Current Nuclear Strategy
        7.5.1 Russia
        7.5.2 China
        7.5.3 India and Pakistan
        7.5.4 UK and France
        7.5.5 North Korea
        7.5.6 Israel
        7.5.7 Iran
        7.5.8 The United States of America
8.0 High Value Anti-Nuclear Activism
    8.1 Tactical Weapons
    8.2 Arms Reduction Treaties
    8.3 Anti-Ballistic Missiles
    8.4 Donations
 

Special Topics

Laser Enrichment
    Laser Enrichment – How It Works
    Laser Enrichment – Proliferation

Changelog

As I receive feedback, I intend to update this post series. All major changes (e.g. not copy editing) will be posted here.

February 5, 2017
  • In 3.0 Proliferation, clarified that the design of a nuclear weapon is at least as challenging as enrichment, if not more so.
  • In 7.5.5 North Korea, clarified my stance on North Korean fizzles and underlined the danger that even relatively small weapons pose.
February 12, 2017
April 1, 2017
Biology, Falsifiable, Science

Skepticism About X-Risk: Viruses and Prions Edition

There are a lot of living things that are quite good at killing humans. Tigers, anthrax, lions, cows, bears, and other people do away with thousands of us each year.

There are a few non-living things that are also quite good at offing us. Good old water manages to take quite a few. In good years, we don’t lose anyone to the nerve gasses sarin or VX (Unfortunately, the last few years haven’t been good ones in that regard).

What about those liminal critters though? Viruses and prions aren’t really alive in the traditional sense. They can replicate, they can even evolve, but they lack the hallmarks of life, foremost among them the ability to reproduce. Both of them find ways to hijack the machinery of living organisms and use them for their own ends.

These self-replicating patterns and their potential to wipe us out are the subject of this blog post.

This blog post grew out of a conversation with my friend Malcolm Ocean. We were discussing all the ways the world could end and our conversation drifted towards the biological. We started with proteins (where my background is) and moved on from there towards viruses (where I make a whole bunch of assertions; if you’re a virologist, please correct me).

Can you engineer a protein to wipe out humanity?

When Malcolm posed this question, my first thought went to Ricin, the incredibly deadly protein poison. A favourite of communist assassins, less than 2mg of Ricin can kill an adult human. But while Ricin is active when inhaled, it’s not the easiest to disperse. Nerve gasses like VX are far more deadly and much easier to deliver and disperse to boot.

For a protein to have any advantage over these tailor made weapons, it would need the ability to self-replicate and jump from person to person as it kills them. Anything short of that and you may as well use something else. When it comes to death, we live in an age that’s a grim parody of a cell phone advertisement ­– whatever you desire, there is almost certainly already a weapon for that.

Unfortunately, there exist self-replicating protein patterns. They are called prions and they’re still poorly understood.

The first prions were probably caused by genetic mutations. These mutations still exist – they’re the cause of diseases like fatal familial insomnia (so named because it is passed down in families, it causes its sufferers to lose the ability to sleep, and because it is invariably fatal).

Prions are mis-folded proteins that somehow catalyze other proteins mis-folding in the same way. This leads to aggregates of proteins. Many neurodegenerative diseases have an element of protein aggregation in them – it’s been implicated in both ALS and Alzheimer’s, for example.

But what makes prion disease unique is their transmissibility. If someone else’s prions get into your brain, they’ll cause the same aggregation process to occur. Suddenly, you have a prion.

We hear about these cases on occasion. Mad Cow (or Creutzfeldt–Jakob Disease) is a prion disease. In cows, it’s known as Bovine Spongiform Encephalopathy (BSE), while it takes on the Creutzfeldt–Jakob Disease (CJD) moniker in humans. Like FFI, it’s invariably fatal. Outbreaks of BSE/CJD occurred because factory farming can involve feeding dead cows to living cows. When cows eat BSE tainted beef, they too contract BSE. One cow with BSE can end up infecting many other cows if it enters the feed supply.

If humans consume any part of the brain of an infected cow, the prion can end up in us. Evidentially, there is enough similarity between the underlying protein for the cow prion to catalyze the formation of aggregates in human hosts.

We’ve gotten better at not feeding cows with symptoms of BSE to other cows, which has cut down on the incidences of CJD. In the interim, it killed about 200 people.

It is maybe within the realm of possibility that you could make a prion more transmissible than BSI. Currently the only method of human-human prion transmission is cannibalism (more on that in a moment). This is ill suited to wiping us all out, because cannibalism is uncommon [citation needed].

Perhaps some villainous biochemist could design a prion that gets out of the brain, enters systemic circulation, irritates the lungs, and gets coughed into other people’s faces, where it goes up their nose and (maybe) right past the blood-brain barrier. This is the best I can come up with and I’m pretty skeptical (the Wikipedia article points out we’ve yet to successfully transmit anything therapeutically relevant across the blood brain barrier).

But begging the question of plausibility and assuming this could happen, has our biochemist created a civilization destroying plague?

Enter the Fore people. They live in Papua New Guinea and they practiced ritual cannibalism – they ate their dead relatives. Like out BSE infected cows, some of these relatives had prions. In this case, the culprit prion is known as Kuru.

Eating prion laced brains is not a recommended survival strategy. It tends to lead to contracting prions yourself. And indeed, many of the Fore people contracted Kuru from their cannibalism.

Remember how I said that prions are invariably fatal? So is being alive (at least, for now). Sometimes people with prions don’t die of prions because something else kills them first.

Evolution optimizes for reproductive success. In the funeral practices of the Fore, children and the elderly ate the brains. Prions tend to kill people in a few years. A few years really isn’t enough time for young children to beget the next generation.

Imagine the spread of Kuru. The first sufferer dies from it and is consumed. Years later, those who ate her begin to show the same symptoms. They in turn die and are consumed. The infection spreads exponentially, but slowly, first in bursts every few years, but eventually continuously as the differing survival times lead to staggered deaths.

But humans are wonderfully diverse. In each group of infected, there would be those who, by some quirk of biology, survive longer. Invariable or inevitable doesn’t mean quick. Those who survived would reproduce. And whatever quirk of their physiology allowed them to last longer against Kuru would be passed down to their offspring.

If you aren’t a member of the Fore people, Kuru would kill you in a few years. But if you’re a member, you might survive thirty years after contracting it. Thirty years is plenty of time to die of something else.

Even in a small, isolated ethnic group in Papua New Guinea, there was enough genetic variation for the genes that protect against Kuru to be “found” and amplified.

Imagine our hypothetical prion plague spreading across the globe. It would kill many, many people, but it would kill most of them slowly. They would have time to pass down their skills, to shut down any reactors they were in charge, etc.; essential to prepare for the end of their lives in an orderly fashion.

And among these people, there would be some who are mostly unaffected and some who are completely immune. It would be a crap-shot ­– we’d need immense amounts of coordination and altruism to pull through this sort of prion pandemic. Or rather, our current society would require desperate measures if it were to survive. Humanity would come out – if not fine, then alive. Living without running water and antibiotics isn’t pleasant, but we pulled it off for half a million years and we can (hopefully) do it for another half a million if we have to.

What about a virus?

Ebola killed roughly 8,000 people in 2014. Influenza killed about 4.5 times that many people. In the USA alone.

Ebola infected about 30,000 people in its worst outbreak ever. Influenza infects 200,000 people in the USA each year. The common cold infects an incalculable number of people.

Ebola grabs all the headlines. The flu is the target of a new vaccine every year. And yet the common cold is more reproductively successful, when we look at total number of people it infects.

The common cold is successful because it is so mild. You get the cold and feel like shit, but you’re still mostly okay to go out and work. Your partner will still kiss you. People might still sit next to you on the train. And so the virus gets passed on.

When you get influenza (the real deal, not the 24 hours of stomach pain sometimes called the flu but in reality caused by food poisoning), it tends to floor you. Even partners do their best to limit their exposure to you and your boss wants you well away from her, thank you very much. And so you pass it on to fewer people.

When Ebola is in a city, people become scared to even leave their homes. All non-essential social contact stops. Transmission is rare.

I know I’m comparing apples to oranges here – influenza and the common cold are both airborne and Ebola is not.

But stop and think about what these case numbers mean. We often portray viruses as an inimical threat, as organisms hell-bent on our destruction. This is false. This is false for reasons beyond the inherent mistake of ascribing agency to non-sentient machines.

Viruses are replicating patterns that need the machinery of another organism to replicate. They are the simplest possible parasite. Viruses without hosts are just inert RNA or DNA in a thin protein coating. Viruses need their hosts, insomuch as they need anything.

Ebola isn’t particularly dangerous to human civilization because outbreaks of Ebola tend to burn themselves out. It kills more quickly than it can be transmitted. And so transmission stops and the viral particles again become inert.

Viruses that kill their hosts too quickly face selective pressure to slow down. This can occur over the course of an outbreak too. Is it any wonder that the strain of Ebola that caused a particularly large outbreak ended up being less likely to kill than most other strains?

Maybe this is actually just the result of better care. We’d need to run a lot of sequencing of a lot of Ebola samples to be sure. But we know how selective pressure on viruses work and those models would predict that this strain of Ebola evolved to be less virulent over the course of the epidemic or was more successful because it was less virulent from the start.

There’s an opposite pressure that bears mentioning here as well. Viruses can’t go too far in the other direction. They need to be fairly virulent if they want to spread successfully. Each virus particle is another chance to infect another host. They want their current host to make a lot more of themselves. They’re just incentivized by evolution to do it at a reasonable pace.

I came at this point the long way around, but here it is:

Any “super” virus created in a lab will face this selective pressure.

In parallel to this pressure, humans will face an immense selective pressure for immunity or resistance.

The end result of the release of any virus engineered to kill all of humanity would probably be a new equilibrium. The virus would tend to become less virulent with each case and many survivors (and everything we know suggests there would be survivors; even HIV and rabies don’t get everyone) would probably have an innate resistance that they could pass on to their children.

Perhaps you’ve come up with a super-virus and are aware of this problem. You know your virus will eventually betray you and become less virulent, so you decide to trap it in amber, so to speak.

Viruses tend to have poor DNA or RNA replication machinery. This results in lots of errors every time they reproduce. With many viruses, you can tell the number of them inside a cell by the number of variations in the genome. Their copying machinery is so error-prone than every single virus has a mutation.

But you don’t want that, so you give your virus the best possible DNA/RNA replication and repair machinery. Its DNA/RNA will be exactly as you intended it in every single copy. It won’t become any less virulent now!

You’ve done two things. First, we’ve already established that some people will be immune. If your virus doesn’t evolve at all (and evolution requires variation for selection, which requires mutation), then these people (and all their descendants) will always be immune.

You’ve also just given whoever has to come up with the vaccine and other treatments for it an orgasm.

You know the flu shot that you don’t get? The one that you’re supposed to get every year because the surface of the influenza virus changes every year and you lose any immunity to it? This is because of influenza’s bad RNA replication mechanisms. It’s the same with the common cold. This isn’t true for many viruses. Once you get chicken pox, you’ll probably never get it again. Your body has learned its surface markers and knows to kill them on sight. These markers change very rarely, so your immunity doesn’t expire.

These changing markers are the best (and only) defense a virus has against vaccination. Take that away from them and vaccination becomes much easier.

Vaccination isn’t the only thing that becomes easier when viruses don’t evolve. We’ve had designer drugs for fighting viruses for a while now. Spurred on by the crystal structure of HIV integrase, scientists have begun to figure out how to take the structure of a virus and develop molecules likely to stop it.

It is true that HIV can evolve around some drugs. This is why we’ve switched to regimes of drugs, which combine several medicines with different routes of action. This strategy is much more effective at preventing resistance. Instead of needing one mutation to develop resistance, the virus must develop several, all at once. This almost never happens, even in fairly fast changing viruses. In one that was deliberately fixed it would be almost impossible.

Here’s what the response to a large scale bioengineered pandemic would look like:

  1. People would start showing signs of infection. Doctors, confused by the mortality rate and the rapidity of the spread would eventually send it off for sequencing (I’m eliding a host of difficulties here, but they’re solved difficulties; simple doesn’t mean easy).
  2. Sequencing results would come back and show that this virus is something new.
  3. There’d be a quarantine. In addition, people in unaffected areas would reduce the time they spend outside their houses as a precaution.
  4. As the death toll mounts, more and more scientists would begin working on the virus. Several avenues would be exploited in parallel.
    • A vaccine would be developed using conventional techniques
    • Large scale, massively parallelized and automated efforts would be undertaken to get the virus crystal structure
    • Antiretrovirals, antivirals, and the kitchen sink would be tried on affected patients in the hopes that something would serendipitously work.
  5. Something would work. We’ve done this too many times now not to have the process figured out. At this stage:
    1. Either the pandemic had good DNA/RNA repair machinery, in which case scientists would be slightly surprised by the lack of resistance to treatment. Not having to work around resistance would allow doctors to give patients only the cheapest or best tolerated treatments, reducing the economic or human toll of the disease.
    2. Or the pandemic is free to evolve. In this case, we’ll see a steadily decreasing lethality rate. Part of this would be natural evolution and part would be the effort of scientists. Fully annihilating it would be hard and will probably take decades, but increasingly effective combinations of therapies would be developed, killing off even highly resistant strains.

If your next work of fiction involves a virus or prion killing all the world’s population, I’m sorry. May I suggest writing about nukes instead?

Epistemic Status: Falsifiable