Brother, can you spare a moment to talk about isotopes?
You remember isotopes, don’t you? From high school chemistry?
No? Well, you remember atoms at least? Yes? Tiny little things. Made of protons and such? Yes? Excellent. Let us review.
Each element has a number. Hydrogen is 1, copper is 29, polonium is 84, and so forth. This number corresponds to the quantity of protons in the nucleus. Altering this number changes the atom’s element. Ipso facto.
Contrast this with atomic weight. The sum of the protons and neutrons in an atom’s nucleus determines its weight. One proton and no neutrons makes a hydrogen nucleus, but so does one proton and two neutrons. More than that, and you start to get some stability issues, but we’ll cover that in a bit.
These different weights are called isotopes. Sometimes we use vernacular names for them, as with deuterium and tritium (both are isotopes of hydrogen, H-2 and H-3, respectively). Most of the time, it’s easiest to use the chemical notation, particularly with the heavier atoms which often have several stable isotopes (for example, osmium has five).
Isotopes aren’t terribly important for ordinary chemistry. In chemistry, the important bit is how electrons interact, and electrons are a function of protons; we care about atomic number when we want to form molecules and such. Isotopes are relevant for nuclear interactions.
Nuclear interactions are how I solved my Brainbash problems.
Most naturally-occurring isotopes are stable. Unstable isotopes, like their name suggests, tend to decay toward stability. Here, nature is quite versatile. Atoms can spit out protons, neutrons, or alpha particles (two neutrons and two protons in a little cluster) from their nucleus; they can spontaneously convert neutrons to protons (beta decay) or protons to neutrons (positron emission); they can yoink an inner-shell electron to convert a proton to a neutron; or they can just spontaneously undergo nuclear fission, which is when the nucleus violently dissociates.
It is this latter process I have recently found myself immersed within, hence the long delay between updates.
Contrary to what the movies might suggest, you can’t just mash a wad of uranium or plutonium together and get a big ol’ explosion. If you want fission, you have to make it happen. That ain’t as easy as you might imagine. Under normal circumstances, uranium is not particularly radioactive. U-238 alpha decays with a half life of something like four and a half million years. It is only fissile after absorbing a neutron, and even then the most common isotope still won’t usually split on its own.
So, where do we get neutrons?
Commercial neutron sources tend to be Cf-252, and a cheap one will set you back around $15 grand. Unfortunately, I would have a hard time justifying that particular credit card line item with the missus. Home kit neutron sources lean more heavily toward either beam-tube deuterium generation (blech) or a gamma-beryllium device.
In general, I emphatically advise against tinkering with beryllium. It is extremely toxic, and the cancer you are almost guaranteed to develop after inhaling a bit of it is notoriously aggressive and pretty much incurable. However, you probably have some Be in your home, whether in your golf clubs, your car brakes, or in the spokes on your bicycle. If you know where to look, there should be enough in your house or local junkyard to make your own DIY neutron source, provided you have an appropriate gamma source to activate it (also you should know enough backyard metallurgy to extract it from the alloy, obviously). I recommend modifying the magnetron you have in an old microwave you don’t mind destroying to generate the requisite gamma radiation.
So now you’ve got some neutrons. Congratulations! They are basically useless. So far.
If you want your device to produce a decent yield, you need a good chain reaction, which means that a) your starter neutrons need to be at the proper energy level to generate a fission event and b) the neutrons born from fission also need to be at the proper energy level needed to induce fission.
My editor informs me that I should omit mention of specific parameters in this section, so please forgive the vagueness that follows.
Not all ionizing radiation is created equal. Neutrons ejected from a fission event will be considerably more energetic than those from your little homebrew beryllium agitator. The real trick to designing a good warhead lies in matching neutron energy levels with the proper absorption cross-section in your fissile material.
You know the trick about throwing pasta at a wall to find out if it’s done? Nuclear physics is a little like that. The neutrons have to be al dente. And each isotope has a different appetite. U-238, the most abundant isotope of Uranium in nature prefers fast neutrons. Anything more energetic and it’ll decay almost instantly via mere neutron ejection. Anything too slow and it’ll beta decay into Neptunium (a step toward Plutonium, where we want to get). Isotopes like Pu-239 and U-235 prefer thermal neutrons, a bit less energetic than what you get right after fission, but not by all that much. It is relatively easy to slow a neutron down. It is quite challenging to speed one up on the fly.
The alternatives were to either breed up some Plutonium (you normally need a reactor larger than I can fit in my garage for that) or to enrich common uranium ore to extract the U-235 isotope. I didn’t have nearly enough ore for enrichment. If memory serves, Los Alamos needed over 1000 tons of ore to make Little Boy. I live in a townhouse just outside the DC beltway. I don’t have space for either the ore or the centrifuges. However, what I can do is to turn that little beryllium device made out of old brake linings I got from the local junkyard into a neutron injector, so to speak.
Uh, also I doubt I could get a thousand tons of uranium ore without attracting a bit of unwanted attention. In fact, it’s probably best I don’t disclose too much about where I got the uranium I ended up using for this little project.
I won’t bore you with the details, but it turns out that you can easily convert neutrons into protons by passing them through a particular medium. Proton ejection can be induced in certain materials you can find in sufficient quantities at, say, children’s birthday parties. Once ejected, a simple muffler pipe cyclotron can accelerate the charged particle to sufficiently high energies to be useful for our purposes here. After they are sufficiently boosted, go ahead and ram those protons into another medium (again, one found in abundance in the common American household) to get neutrons back out. If you account for energy loss in the conversion process well enough, you can get the proper step-up voltage dialed in with minimal effort. Now just aim the emitter at your fuel, and let nature take its course.
It took me about two weeks to turn [amount redacted] of raw U-238 into useful Pu-239. I obviously had to take great care to trap the stuff, since it’s incredibly toxic in addition to being low-grade radioactive. Military-grade duct tape proved helpful.
In the meantime, I had the dubious joy of making a trigger mechanism. The simplest design I know is to slap two just-barely subcritical masses together to create a prompt critical mass.
Little Man used a cordite-driven shockwave to force a U-235 collar onto a stationary slug of the same material. Modern designs are a lot more complicated, and rely on precise timings of more sophisticated high explosives. Cordite is pretty cheap, and you can get it from most any sporting goods stores. I got mine at the Cabela’s in Gainesville. Great store. Very friendly staff. The parking lot takes a little getting used to, but that’s my only quibble with the place.
I altered the design a wee bit by making my plug and collar conical, in the unlikely event that the conventional shockwave might shift the plug. I also used a brass casing to contain the cordite since I happened to have the scrap on hand. The last step was to actually make the plug and the collar.
This is easier said than done. Plutonium melts at a shade under 1200°F (compare this to 2800°F for iron), but this is still hot enough to be a problem in my little single-car garage. Cinder blocks once again proved their worth. A glazed ceramic interior shield kept the heat where it needed to be as I incinerated the duct tape bit by bit and collected the metal in a series of molds next to my surplus Geiger counter (it isn’t actually a Geiger counter specifically, but it is a radiation detector, and I doubt most people reading this would know all that much about the milsurp model I use). This was, to say the least, the most harrowing step of the process. I had no way of knowing ahead of time how well my ad hoc breeder had worked apart from a few limited chemical tests. Add too much plutonium in one place all at once, and there would be a very large crater in my sleepy neighborhood centered on where my modest little commuter car once parked.
I found that preparing the most optimistic calculations beforehand and including generous confidence intervals saved me a bit of worry, but it might have also extended the time it took to assemble the bits and pieces. Not that it mattered all that much. I still finished in time to detonate the device before the Halloween night lunar ritual could be completed.
Getting back to Brainbash turned out to be easier than I imagined. I circled the state thrice widdershins, as Gladys suggested, and drove west to east on the lost, lonesome byways. And behold, past dusk in the midst of a great fog did the thrice-cursed town again greet me.
Except this time I had a nuke.
To make an already very long story short, I seem to have gotten a decent yield out of it. My Korean buddy riding shotgun managed to deftly clear out the pork rind ruminants peppering me with solicitations to “enjoin the beckoning” or whatever the hell those eyeless miscreant abominations were bleating at me. We had a blessedly clear line over the next ridge, whereupon I dialed the appropriate phone number to start the countdown.
It was night, but we wore sunglasses to protect our eyes from the flash. Itak gave me a thumbs up as the atomic flash lit the forsaken night and I rolled down the window to flip Brainbash the bird for one last time.
Rot in lunar hell, Apocolothoth. You will never make it to our beloved Earth.
Also, it seems that my wife and child are feeling much better, so we’ve got that going for us. Which is good.