The USS San Francisco was just hours away from getting underway. It was time for us to bring her to life. I was standing an Under Instruction watch in Engine Room Lower Level with Jay-Jay during the startup. We were just a couple of dudes in the Engine Room when—wait. Sorry. Forgot. There are no dudes in the Engine Room. Okay, so we were just a couple of Petty Officers in the Engine Room, when the Engineering Officer of the Watch way up in Maneuvering made the announcement:
“THE REACTOR IS CRITICAL!”
That’s the exact the announcement I heard during my very first startup aboard the USS San Francisco, all the way down in Engine Room Lower Level.
What? The reactor is critical? Everybody run! Pandemonium!
That’s what happens on the USS Enterprise in Star Trek! Airtight doors start lowering. White smoke starts roiling. Escape pods start becoming scarce. And here I was in real life back in the engineering spaces of the USS San Francisco when I heard those very words. “THE REACTOR IS CRITICAL!” I had so many questions and immediately turned to Jay-Jay for answers.
“Did you go out last night?”
“No. You?”
“No, but I did the night before.”
“You get laid?”
“Actually yes. Yes I did.”
“Nice. Was she any good?”
“Uh… yeah, I’d say exactly average from my perspective.”
“Big tits at least?”
“Biggest I’ve ever had.”
“Nice.”
I wasn’t about to admit that it was my first time ever or that I paid for it. You know, gotta play it cool around the guys. Yeah, I’m cool. I’m totally cool. Oh, and what about that reactor going critical nonsense in the middle of our shoot the shit? Eh. Whatever. Who really gave a crap besides the twidgets? Not us. Why the Engineering Officer of the Watch even bothers to make such announcements, I don’t even know. Like, we don’t care, dude. Go tell a twidget. I continued the shoot the shit with Jay-Jay.
You see, it was the wee hours of the morning, and we were starting up the reactor plant and engine room in preparation for getting underway. We didn’t have much to do just yet carrying out Operating Instruction 27. But the reactor going critical at this time was actually a good thing. While studying at Naval Nuclear Power School, the instructor made an analogy which should put this all into perspective:
“When the Engineering Officer of the Watch declares that the reactor is critical, it’s sort of like a guy starting up his car, turning to the passenger and stating, ‘The engine is running!’”
That’s not a perfect analogy as one doesn’t simply turn on a reactor; it’s a complicated process. And for as many parts as an automobile engine has, it is really quite simple compared to a reactor plant. I’d say a gasoline engine has more in common with a balloon than a nuclear reactor. Still, the analogy is close enough to make a point. The critical reactor is online. But why not just state that? What does the term critical actually mean? What is it based on?
Okay. Criticality of a reactor is based upon neutron count, and that neutron count is directly proportional to power. When the reactor is critical, it means the same number of neutrons have been produced in this generation as had been produced in the previous generation. A reactor that is critical, in plain terms, means a reactor that is making steady-state power. So, settle down there, and for the love of god, could you please get out of that damn escape pod already!?!
Yeah, but what if there isn’t the same number of neutrons produced in this latest generation as that which had been produced in the previous generation? There might me more! Good question, fictitious person sitting in a non-existent escape pod I’m responding to in my imagination. So, when fewer neutrons are produced in each subsequent generation, we call this reactor state subcritical. It simply indicates reactor power is being reduced. When more neutrons are produced in each subsequent generation, we call this reactor state supercritical. It simply indicates reactor power is on the rise. And no, the Engineering Officer of the Watch isn’t all over the announcing system declaring each and every time the reactor changes state.
Reactor is critical. No wait, it’s supercritical. Umm… now it’s subcrit—wait, carry on, it’s just plain critical again. Shit, it’s supercrit—this fucking thing.
No, no, no. Only that one time during the startup when it reaches initial criticality, in which technically the reactor is in a supercritical state as power is on the rise. Details. But hell, could you imagine the pants pooping that would occur on the Enterprise if the Engineer announced that the core had gone supercritical!?! That would make for some exciting television!
So, the startup had begun. The reactor had reached criticality. That twidget in the box—or Reactor Operator in Maneuvering if you wish to maintain decorum—had raised his control rods to a previously calculated height to start up the reactor. This is called the Estimated Critical Position. The ECP calculation takes into account where the reactor is in its lifespan, the power history before the last shutdown, the time since the last shutdown, the temperature of the coolant, and probably a bunch of other crap I have long since forgotten.
The RO and the EOOW did a good job with their ECP math. You know they did a good job because they didn’t make the reactor explode. That’s way beyond supercritical into an uncontrollable region called prompt-critical. They went prompt-critical on the Echo class Soviet submarine K-431 once. The subsequent explosion ruptured the sub’s pressure hull, killed ten people instantly, and contaminated a nearby forest. I guess that’s one way to get out of an underway.
Since we didn’t go prompt-critical, I didn’t care much about this stupid, boring, early morning, while-the-cute-little-snug-as-a-bug-coners-are-all-still-sleeping-soundly startup. No, not until the reactor was in the power range and self-sustaining. They’ll make that announcement. They’ll make a lot of announcements. Right now, we were in the source range. There aren’t a lot of neutrons to count, so we’re using those ultra-sensitive source range instruments to detect them.
We’ll transition to the intermediate range instruments before the neutrons saturate the source range instruments and burn them out, and then finally to the power range instruments for the same reason. Now we have a lot of neutrons to count! (Which if you remember, is directly proportional to reactor power.) Once in the power range, the reactor core is making enough power to heat the coolant, which in turn will produce steam in the boilers.
Wait. Boilers on a nuclear submarine? What the!?!
Well, yes, there are boilers on nuclear submarines. We call them steam generators, however, because we’re fancy. And I’m not sure if what I just wrote is surprising. Maybe it is, maybe it isn’t. But yes, the most complicated and technologically advanced machine ever created this side of the space shuttle is, well… it’s a steam ship. Yes, a nuclear submarine is really just a fancy type of steam ship.
And the reactor, often pictured in movies as something with glowing green or purple rods and making all sorts of bright, blinding light and some undefined type of “power,” really just makes, well… it simply makes heat. Nothing magical, just the lowliest form of energy. Yes, the nuclear reactor in function is not unlike the water heater in your basement which gives you a nice steamy shower in the morning.
So, two years of training at an advanced school crammed full of nuclear physics and supposedly deemed the third most difficult undergraduate level course after I think it was some Harvard and Yale programs was all to ultimately learn how to, well… it was all about how to boil water. Yes, essentially that was my job. Boil water. Make steam.
We use this steam to propel the ship and create electricity, which may be impressive on its own right, but the portion between that and the reactor core is decidedly and disappointingly low tech. Machinist’s Mates on a World War One era battleship could operate our engine room, no sweat. They would just have a wee bit of trouble trying to figure out where to put all the fuel oil from the tanker they just ordered.
Silly battleship bubbas! This ship is atomic! You know, the absolute highest tech available back when Bettie Page was playmate of the month. Oh, but this 1950’s technology is indeed impressive. How many people can say that they split atoms for a living? Just another day at the office. Yeah that Einstein E=mc2 formula? No biggie. It’s just what we do here.
To be honest, nuclear physics really isn’t that hard to grasp. I’m not saying all the scientists who experimented and discovered just how exactly to split atoms had a cakewalk, mostly reading the paper leaning back with their feet up sipping on a few nips of gin hidden in their desk at work. No, all I’m saying is that once they figured out how all these little particles and waves worked together, the concepts then became not that difficult to comprehend.
Hell, I think even a coner could understand it. Or maybe not. That’s why they’re coners. Many a coner had actually attempted the Navy Nuclear Peepayleenay but flunked out and were reassigned to other submarine duties away from the reactor. (Those particular coners are what we referred to as “nuclear waste.”) But I digress. Where were we? Oh yes, nuclear physics isn’t really that hard to grasp. Allow me to explain.
So here I’m going to do the briefest explanation of how nuclear fission works that I could possibly do. Kind of have to. I mean, this is a memoir of someone who lived on a nuclear submarine. It would be like a chef writing a memoir and not throwing in a recipe or two with shallots and truffles and other shit I’ll never ever have in my kitchen cabinet. Okay then, I’m starting off quite basic, which may be insulting to some. Maybe most. And fair warning, this crapola is mighty dry. If nuclear physics isn’t your jam, might be time to skim or simply jump between the two solid lines.
_________________________________________________________________________
Okay. Here we go for those non-jumpers. First off, there’s the construction of the atom. Any atom. It is made of three components: protons, neutrons and electrons. Right off the bat, we’re going to dismiss the electrons after their description. These suckers are absolutely tiny compared to protons and neutrons, which are nearly two thousand times the size. These electrons orbit the core—or nucleus—of an atom like little satellites, and they are negatively charged. But for the most part, we disregard electrons in nuclear physics. Electrons are for the chemists. They’re essential for understanding chemical reactions, not nuclear reactions. In fact, they are so inessential to most nuclear reactions that physicists renamed them beta particles.
Protons and neutrons are located in the nucleus. For this reason, they can both be called nucleons. These two nucleons are roughly the same size, but there are two major differences. The first difference is that protons have a positive charge whereas neutrons have no charge whatsoever. The second difference is that if you alter the number of protons in the nucleus, you alter its chemical identity. You actually change what element it is. Altering the number of neutrons is rather anticlimactic. You still have the same element, but you’re affecting its nuclear stability.
For example, if you have eighty protons, then you have mercury. Remove one proton, and holy cow! You got gold! Remove one more, and hot damn, you have platinum! That’s alchemy! If you instead added two protons to your mercury, you went the wrong way and just made lead, you stupid dumb failed alchemist. You’re fired! Well no, that’s not how that works. We can’t actually inject or directly eject protons in a lab as far as I know. We can, however, bombard atoms with neutrons in hope of injecting one into the nucleus.
If you were in that business of injecting neutrons into atoms, starting from the first element and working your way up, for the most part, your life would be dull. You’re no alchemist. So, you just added neutrons to hydrogen? Well it’s still hydrogen. (It does get special names like deuterium and tritium however. But it’s still just hydrogen.) Now you added neutrons to that mass of iron over there? Well it’s still iron and you know what else? You don’t even get special little names for those new versions. Oh, so now you added neutrons to that mass of plutonium? Well it’s still pluto—holy hell what did you just do!?! You just made zirconium and xenon! And a gargantuan amount of energy! And why is your hair falling out and skin blistering?
Oh, that’s right, tinkering with your element’s neutrons won’t directly change what element it is, but the instability you introduce might just split that atom apart into two different elements while producing heat and radiation. That’s fission! There aren’t many atoms capable of practical fission, so most of the time nothing significant will happen when injecting neutrons other than the fact you can start using the word isotope like a boss. Those are different versions of the same element based on how many neutrons are present.
Uranium-235 and Uranium-236 are different isotopes of the same element, the difference being one neutron. Those numbers at the end are the mass numbers, which are the total number of protons and neutrons. The atomic number, in contrast, is the total number of protons only. So, in this case, both U-235 and U-236 have the atomic number of 92 as they both contain 92 protons. Since they have different mass numbers of 235 and 236, subtracting 92 for the protons means one particular isotope of uranium has 143 neutrons while another has 144 neutrons. Same proton count, same atomic number, same element. Different neutron count, different mass number, different isotope.
And one other thing about the word isotope. Remember how I said electrons are disregarded because they’re kind of just for the chemists? Well, the word isotope is kind of like that too. It’s more for the chemists. The physicists prefer to use the term nuclide. The two terms are more or less synonymous, but there’s maybe one tiny little difference. Isotope implies, ever-so-slightly, the notion that you are comparing different versions of the same element. Nuclide in contrast implies, ever-so-slightly, the notion that you are referencing a unique and distinct standalone nucleus. It’s a subtle difference. In Naval Nuclear Power School, we called them nuclides because we’re pretty sly.
So, about that atom splitting business. Why do some isoto—I mean nuclides fission when a neutron is absorbed? To understand that, we need to discuss a couple of the four fundamental forces in the universe. When I was in the Naval Nuclear Power School portion of the Peepayleenay, those forces from strongest to weakest were nuclear force, electrostatic force, magnetic force, and gravitational force. Turns out that’s old news. Imagine my surprise when I went to doublecheck this for writing and discovered that they combined two and added another. So, these are the four fundamental forces now: strong nuclear, electromagnetic, weak nuclear and gravitational.
We used to just need to understand the nuclear force and the electrostatic force to understand fission. Now you have to understand the strong nuclear force and the electromagnetic force. Nothing has really changed there other than adding “strong” and changing “static” to “magnetic,” so we can still get on with this explanation. And no, we don’t have to learn about the weak nuclear force. No idea what that is. Guess I have some reading to do after this, but once again, I digress.
Okay, so the nuclear force is the strongest force in the universe. Wait. Make that the strong nuclear force is the strongest force in the universe. Sorry. Still getting used to saying that. It is a force of attraction, but its range is finite. Very, very finite. Like limited to the distance of about three femtometers, which is three meters to the negative fifteen power. That’s roughly the length of two nucleon diameters, or a distance equal to the average length of two Navy nukes’ penises tip to tip, if you were to ask them. We are a self-deprecating bunch. Hmm. Let’s just stick to the finite range of only two nucleon diameters. More apropos here.
Now we must compare the strength, range and direction of the electromagnetic force. It is the second strongest force in the universe, but it is no match for the strong nuclear force. Not even close. However, its superpower is that its range is to infinity and beyond. This force’s kryptonite is that its strength diminishes significantly over distance, specifically by the inverse square of that distance. As for direction, the electromagnetic force can be one of attraction or repulsion. Opposites attract, so on account of protons all having the same positive electrostatic charge, it’s quite repulsive all up in that nucleus.
So, are you picturing the construction of the nucleus now? No? C’mon, stay with me here. This is important. You have this atomic core of protons and neutrons being held together by the strong nuclear force, not unlike love, but also with this little bitch electromagnetic force trying to break the protons apart like they were gossiping about a certain couple everyone is jealous about. Not to worry, right? Gossip can’t overpower love, right? Well, something significant happens with respect to those two forces as the size of the nucleus increases.
I suppose if we stick to my love verses gossip analogy, I should point out that these nuclei are significantly polyamorous. The core is a cult, okay? So, at first the energy binding each nucleon together becomes greater. Then due to the size and geometry of the nucleus, and the limited range of the loving strong nuclear force, it eventually begins to weaken again. The unlimited range of the gossipy repulsive electromagnetic force is beginning to have an effect on the bonds. This is right around the point you have sixty nucleons, closest to the elements iron and nickel. They are the most tightly bound. Take a look at the binding energy per nucleon of selected nuclides here, and you can see the pattern. The units are in Mega-electron Volts, a measurement of energy.
Hydrogen-1/Protium (0.00 MeV)
Hydrogen-2/Deuterium (1.11 MeV)
Hydrogen-3/Tritium (2.83 MeV)
Helium-4 (7.07 MeV)
Carbon-12 (7.68 MeV)
Oxygen-16 (7.98 MeV)
Neon-22 (8.08 MeV)
Silicon-28 (8.34 MeV)
Iron-56 (8.79 MeV)
Nickel-62 (8.79 MeV)
Zirconium-90 (8.71 MeV)
Iodine-127 (8.44 MeV)
Xenon-140 (8.29 MeV)
Gold-197 (7.91 MeV)
Lead-208 (7.86 MeV)
Plutonium-239 (7.56 MeV).
It’s plain to see that binding energy per nucleon shoots up rapidly from hydrogen, tapers off a bit, peaks at iron and nickel and falls off gradually. Can you picture that list of numbers above as a “binding energy per nucleon” curve? The important thing to understand is that for your nuclear reaction to release energy, the product nuclei need to be more tightly bound than the original nucleus. Sure, you could split helium into two less tightly bound deuterium nuclei, but that would be an energy absorbing endothermic nuclear reaction, not an energy releasing exothermic nuclear reaction.
So, looking at that binding energy per nucleon curve in your mind, I think it’s plain to see that in order to maximize the release energy from fission, you’d want your products of fission to have mass numbers greater than sixty, and therefore you would want to start with a large nuclei. Of course, the opposite is true when talking about fusion. In order to release energy from fusion, you’d want your product of fusion to have a mass number less than sixty, and therefore you would want to start with two small nuclei. For example, fusing two deuterium nuclei into a much more tightly bound helium nucleus would be a desirable exothermic reaction.
But we’re not talking fusion here. We’re talking fission. And for fission, we’re talking splitting big nuclei. The bigger the nuclei the better, as there is more repulsive electromagnetic energy acting upon the protons trying to split them apart. So, let’s go all the way to the primordial element with the greatest number of protons. Uranium!
Wait, wait, wait. What about plutonium? It has more protons than uranium! Well yes, that’s true. It has 94 protons to uranium’s 92, but plutonium is not a primordial element and therefore quite rare. A primordial element is one which was (theoretically) created in the Big Bang. Plutonium is a trace element. It is only present in very small quantities due to beta decay of uranium and neptunium. Beta decay is when a neutron no longer identifies with being a neutral particle and decides to become a positively charged proton. Poof! It ejects a beta particle and is suddenly a proton. Probably has something to do with the weak nuclear force.
In contrast to plutonium, uranium is far more abundant on Earth. Uranium is more abundant than silver, gold and platinum combined. Unfortunately, naturally occurring terrestrial uranium is 99.27% Uranium-238. This is unfortunate because U-238 is not fissile. Fissile means it can sustain a nuclear chain reaction, which U-238 cannot. This is related to the very high energy neutrons required to trigger fission of U-238. It can and will fission, just not on a practical level.
Fortunately, if you want practical fission, then you’re in luck. Naturally occurring uranium is also comprised of 0.72% of the Uranium-235 isotope, and that is most definitely fissile! If you are however worried that this quantity doesn’t sound like a lot, fear not. It’s more plentiful than any isotope of plutonium, and more importantly, it’s plentiful enough to last us an estimated two hundred to two hundred and fifty years if present production methods and current consumption rates remain constant. (And maybe in two hundred years, we’ll all be using fusion reactors in our power plants and submar—I mean starships.)
But back to present time and fission reactors here. So, what makes U-235 such an attractive nuclide for reactors is that it has a high microscopic cross section for the absorption of low energy neutrons, which we call thermal neutrons. The engineering unit for microscopic cross section—a measurement of area—is called a barn. Yes, a barn, as in you couldn’t hit the broad side of a barn… with that neutron I suppose. Or in the case of U-235, you really can, as long as we’re talking about those low energy thermal neutrons.
When you bombard U-235 with thermal neutrons, one will be absorbed to create a rather excited and unstable U-236 isotope. While this absorbed neutron can simply be captured, what most often happens is that this kinetic energy of the absorbed neutron plus the shift of the geometry of the new nucleus results in the ability of the repulsive electromagnetic force (gossip!) to overcome the strong nuclear binding force (love!), and then the nucleus is violently ripped apart. The result of this fission will be two daughter nuclides, two or three high energy fast neutrons, lots of gamma radiation and a hell of a lot of internal kinetic energy—otherwise known as heat.
How much energy (or heat) are we talking? Not so fast. To understand the amount of released energy, we must first look at mass. We started with U-235, which has 92 protons and 143 neutrons, and added a thermal neutron to form U-236. We now have 92 protons and 144 neutrons. And then we fission! The products have to have the same total protons and neutrons. Here is a nuclear mass balance equation with one of the many possible fission products:
U-235 + n –> U-236 –> Xe-140 + Sr-94 + 2n
In this particular recipe, the fission products here are Xenon-140 (54 protons/86 neutrons), Strontium-94 (38 protons/56 neutrons) and two fast neutrons. Xenon’s 54 protons and Strontium’s 38 protons add up to Uranium’s 92 protons. Adding Xe-140’s 86 neutrons, Sr-94’s 56 neutrons and the 2 fast neutrons makes a total of 144 neutrons. Notice that 92 protons and 144 neutrons equal 236 nucleons, the same number nucleons in U-236. We are balanced!
Okay, okay. I know this is dry. Your eyes are probably glazing over, and there may be a desire to start skimming ahead by now despite previously wanting to hang tough. Or maybe you started skimming a while back when I suggested it, and accidentally landed here. For the love of god, where are the drinking stories already!?! But I can’t stop here with unfinished talk about atom splitting and just start talking about pants splitting shenanigans in the streets of Sasebo yet. We’re about to get to Einstein’s mass-energy equivalence. You want to be able to use E=mc2 properly right? Then we need to discuss the mass number of a nuclide verses the actual mass of the nuclide.
As I mentioned earlier, the number of nucleons in an atom is called the mass number. If you want my opinion, mass number should be renamed to nucleon number. This so-called “mass number” isn’t precise enough for Einstein. So, let’s get precise for him now. It’s the least we can do for him after all his bad hair days. Let’s break out the exact masses of the nuclides from the balance equation above—well to seven significant digits at least—using a unit called atomic mass units or amu. One amu is roughly, but not exactly, the mass of one neutron or one proton.
U-235: 235.0439231 amu
n: 1.008664 amu
Xe-140: 139.9216357 amu
Sr-94: 93.9153599 amu
So, let’s see if this math works out when using the exact masses of each nuclide and nucleon. We start out with Uranium-235 and one neutron:
235.0439231 amu + 1.008664 amu = 236.0525871 amu
And then we end up with Xenon-140, Strontium-94 and two neutrons:
139.9216357 amu + 93.9153599 amu + 2 x 1.008664 amu = 235.854324 amu
Drats! That doesn’t add up! There’s a difference of 0.1982635 amu! What the hell!?! What did I do wrong? No, no, no. I checked and rechecked the numbers. My defective pea brain kind of sucks at arithmetic, but not that much! So, where the hell is my missing mass? I looked all over for it! Well, Einstein found it. He knew where it went. He even made a formula to explain where this mass defect went, and we’re going to use it. Yes, that formula. E=mc2
Energy = mass times the speed of light squared
Before special relativity, there were two separate laws of conservation. One for mass (or matter) and one for energy. Matter can neither be created nor destroyed, only altered in form. Same for energy. Then Einstein said, quote, “Nah, nah, nah. Fuck that shit. Check this out…” Now we have mass-energy equivalence. He realized that you can actually convert matter into energy and vice versa. Not long afterwards, a bunch of people in lab coats proved—some with their lives—mass can be converted into energy. So that’s where my missing mass went. It turned into heat. Now let’s do some math. Please try to contain your excitement.
Since the International Standard (SI) for the speed of light is meters per second, I should convert mass from amu to the SI unit of kilograms. Therefore, the resulting units of energy will be in joules. God I hate SI units. We didn’t use SI units in the United States Fucking Navy. Hell no! We stuck with the Mega-electron Volts for our equations and ended up with British Thermal Units. A BTU is the amount of energy necessary to raise one pound of water in standard conditions one degree Fahrenheit. I like British Thermal Units because I don’t know about you, but I’m a fucking American! And in America, we use Brit—wait. British Thermal Units? Alright fine, let’s use the International Standard units. Joules it is.
So, what is a joule? It is the amount of energy transferred to an object when a force of one newton is applied over a distance of one meter. This is roughly the amount of energy released when dropping a full deck of cards from a tall man’s crotch to the floor. Or my crotch, if I happened to be wearing six-inch heels. That’s a joule. Me in heels dropping a deck of cards out of my asshole. Seems like a good enough reason to use the International Standard.
Okay then. Well, one atomic mass unit is equal to 1.6605402×10-27 kilograms, therefore my mass defect of 0.1982635 amu from above when converted to SI units is 3.2922451×10-28 kilograms. And the speed of light is 2.9979246×108 meters per second. Now we add the Einstein:
Energy = 3.2922451×10-28 kg x (2.9979246×108 m/sec)2 = 2.9589224×10-11 joules
Shit. What does that even mean? Are you glazed over and drooling yet? I think I am. Sorry, but we can’t stop here because that amount of energy is just miniscule. Imperceptible. 0.0000000000296 joules? That’s a tiny deck of cards or a really, really short guy’s crotch. Then again, this is just the energy yield of one atom splitting. Can you fathom the size of one atom? I can’t. But perhaps if we multiplied this by the number of atoms in a mass of something tangible, this would all finally make sense. For this, we need to talk about avocados.
Okay, not really avocados. Avogadro, as in the Italian scientist with a number named after him. His number, Avogadro’s number, is 6.02214086×1023. That super easy-to-remember number is the number of particles in one mole of substance. What is a mole? Well it’s the quantity of a substance with Avogadro’s 6.02214086×1023 number of countable items in it. Yeah, if you collect 602,214,086,000,000,000,000,000 of something, anything, you now have one mole of it. Good job!
Well yeah, that’s a rather incestuous definition relationship, and it didn’t help us at all, did it? No, not yet… until you realize that there is this neat thing about moles. I should come clean here. Like how did this Avogadro guy come up with such a crazy number? Well, he didn’t. They just named the number after him due to some groundwork he laid down. He figured that equal volumes of gases under the same temperature and pressure conditions would have an equal number of atoms. Then some other people did experiments to confirm this. Now the number is generally defined as the number of atoms in twelve grams of Carbon-12. And this makes for a neat trick when dealing with moles.
This neat trick when dealing with moles is that when you’re talking about the number of atoms, then moles are easily converted into grams. This will permit us to relate it to a tangible number. So, we were able to calculate the energy of one atom splitting, and now with moles, we can relate those atoms to an understandable amount of material. All you have to do is multiply the number of moles by the atomic mass unit of the particles, and bam you have grams. Hey! I think they did that on purpose!
So, one mole of U-235 has a mass of 235.0439231 grams. Hmm. I can relate to 235 grams. That’s a tangible number. 235 grams of water would be exactly 235 mL of water, or 7.95 fluid ounces. Therefore, one mole of U-235 has slightly less mass than 8 fluid ounces of water—or coffee. That’s a small cup of coffee at a deli, or “short cup” at an overpriced coffee house.
So you see, to make that 235 grams a tangible number for you, I converted that mass of water or coffee (in grams) into a volume of water or coffee (in milliliters and then fluid ounces). That was so you could picture exactly what 235 grams of something is. However, if we were to convert the mass of uranium into a volume for you to picture, it would not be as large as a small cup of coffee.
Obviously, uranium—a heavy metal—is much denser than water or brewed coffee and would therefore occupy less space for any given mass. Water has a density of one gram per cubic centimeter. Uranium has a density of 19.1g/cm3. So, for water, that 235 grams not only occupies 235 milliliters, but it also occupies 235 cubic centimeters. (Water is typically what standard measurements are based upon.) As for uranium, that 235 grams would be 12.3 cubic centimeters. Since one US quarter is about 0.809 cubic centimeters, that makes one mole of Uranium-235 approximately the size of a stack of quarters about an inch high, or fifteen quarters. (That’s a stack of Euro coins about 28 millimeters high, or twelve Euro coins.)
Okay, now we know some things. We know how much energy is released from the fission of one uranium atom, we know how many atoms are in one mole of uranium, and we know the approximate size of one mole of uranium. Let’s put it all together. Just exactly how much energy is contained within that one-inch stack of uranium quarters? All you have to do is multiply your jewels by your avocados. (Joules times Avogadro’s number.) Each nuclear recipe yields a slightly different amount of energy, but my recipe with xenon, strontium and two neutrons yielded 2.9589224×10-11 joules for a single fission event.
Multiplying that single atom splitting by Avogadro’s number, and the yield in one mole is going to be over 17.8 trillion joules total. But now we’re back to these numbers that don’t mean anything to anyone this side of a super turbo-nerd convention. Okay, let’s compare it to gallons of gasoline then. That’s relatable. In fact, it is so relatable that the US Government came up with a unit of measurement called the “Gasoline Gallon Equivalent” or “GGE.” And in that definition, burning one gallon of gasoline releases 121.3 million joules.
Therefore, one mole of U-235, which is the size of a $3.75 stack of quarters, has the same energy output as burning about 146,900 gallons of gasoline. That’s about sixteen fully loaded tractor-trailer sized tankers. Out of a small stack of quarters! Let’s say your car averages 27 mpg, then your nuclear pocket change packs the same amount of energy as the quantity of gasoline needed to drive your car over four million miles (or 6.5 million kilometers). This distance would take the average American 300 years to drive. All from the stack of your uranium pocket change! (I know, I know. Apples and oranges. Just work with me here. We’ll get there.)
Okay, so if you go back and take a quick glance at Einstein’s E=mc2 mass-energy equivalence formula, you can kind of see how the fission of Uranium-235 could release approximately two million times the amount of energy as the combustion of the same mass of gasoline without doing any math. It’s that “c” in the equation. Remember, “c” is the speed of light. Even if you can’t remember the number exactly, you know that’s one big ass number! And that “c” is squared! If you take anything and multiply it by the speed of light, it’s going to be huge. And then multiply it by the speed of light again? Yeah, you can clearly see that it only takes a tiny amount of mass (m) to get an absurdly large amount of energy (E). That’s how one mole of uranium, which is the size of fifteen quarters, contains the equivalent energy of burning about sixteen tractor trailer tanker trucks worth of gasoline.
And… we’re done with nuclear physics. (Well for now. There’s a bit more as my gasoline to uranium energy equivalency is a somewhat disingenuous apples to oranges comparison as you probably already knew or suspected. I’ll explain why later—critical mass for one thing—but for now we’re done with the physics.) Sorry about all that numbery dryness, but it was necessary.
_________________________________________________________________________
I swear it was the briefest explanation of nuclear fission I was capable of writing, from the anatomy of the atom to the fundamental forces acting upon it, to the energy released upon fission. It was still a lot of writing despite striving for brevity, so I suppose an ultra-brief one-paragraph summary review of the hopefully now familiar fission process is perhaps in order:
There’s this big happy nucleus (Uranium-235). All the neutrons and protons just love each other (attractive strong nuclear force). Unfortunately, all the protons can’t help but to talk mad shit about each other (repulsive electromagnetic force). Then this stranger walks—doesn’t run—into the place (a thermal neutron) and splits the family in two (fission). After the breakup, everyone loses weight (the mass defect). And finally, the place gets hot and steamy from all that post-breakup working out (the mass-energy equivalence).
So, do you now understand fission well enough to explain to someone else? Yes? Well then… you’re basically a nuclear physicist now. Try not to blow up any cities. I mean, think about it. Destroying whole cities is what gave nuclear fission a bum rap in the first place. So, after the atomic bombings of Hiroshima and Nagasaki displayed fission’s tremendous and frightening destructive power, there was an attempt to give nuclear energy a calming public relations makeover starting in 1953 with the “Atoms for Peace” initiative. President Eisenhower addressed the United Nations:
“…My country wants to be constructive, not destructive. It wants agreements, not wars, among nations. It wants itself to live in freedom and in the confidence that the peoples of every other nation enjoy equally the right of choosing their own way of life…
…The United States would seek more than the mere reduction or elimination of atomic materials for military purposes. It is not enough to take this weapon out of the hands of the soldiers. It must be put into the hands of those who will know how to strip its military casing and adapt it to the arts of peace…”
Eisenhower’s vision of peaceful nuclear power was to provide a virtually unlimited source of power for maritime propulsion and electrical generation. Now forty-five years after Eisenhower’s speech, I was helping the crew split atoms for peace aboard my warship.
The atomic material on our boat was most certainly not in the hands of the soldiers; it was in the hands of us sailors. My artistic talents were there to provide non-violent nuclear propulsion so that we could blow up enemy ships and compounds with much more palatable conventional weapons such as the Mark 48 ADCAP torpedo and the Tomahawk land attack cruise missile.
But before we could even think about destroying our enemies, we first had to start up the Reactor Plant and Engine Room, and then get underway. The Engineering Officer of the Watch finally made the announcement that Jay-Jay and I were waiting for:
“THE REACTOR IS IN THE POWER RANGE!”
Won’t be long now for us to bring the Engine Room to life. Maybe another 20 to 30 minutes of heating up the reactor coolant, and then steam would come roaring down the headers. This was the time to do an hourly round and complete a set of log readings. After that, Jay-Jay and I would be busy starting up the Main Sea Water pumps, blowing down steam traps and lining them up to the Main Condensers, and doing my part to start up our portion of the Feed & Condensate system.
The Engine Room Forward watch stander one compartment ahead of us would be opening some rather large Main Feed Water pump discharge “knocker” valves, starting up those big Main Feed Water pumps and then opening some other rather large Main Feed Water stop valves at reactor bulkhead. He had a few steam traps to periodically blow down and then line up to the Main Condensers too. Steam Generator water level control would be in manual mode, but by that point they would station a temporary additional “Feed Station” watch so that the Engine Room Forward watch stander could be free to monitor the rest of his equipment.
To be perfectly honest, we weren’t really overworked down in Engine Room Lower Level or Engine Room Forward during startups. Not compared to what the poor Engine Room Upper Level, Engine Room Supervisor and Engineering Watch Supervisor had to do up there. Equalize around and open the massive Main Steam Stop Valves and Main Steam Cutout Valves, blow down the steam headers, line up the Auxiliary Steam system, start up the Main Air Ejector system, start up the Gland Seal Steam & Exhaust Systems, transfer the more numerous upper level steam traps to the Main Condensers and finally start up both Ship’s Service Turbine Generators. Holy hell that’s a lot of valves to turn!
Down in the belly of the submarine, you can hear a lot of action taking place up above during the start up. The cacophony of sounds included screeching, roaring, rumbling, humming, whistling, whirring, whining and banging. What the hell are they doing up there!?! This is the silent service for crying out loud!!! You wouldn’t know that standing in the engine room of a nuclear submarine, however. It’s loud. Loud as hell. And like hell, all this time it’s getting hotter and hotter and hotter and hotter. There’s steam coming out of everywhere. Starting to sweat my balls off! After a lot of work and quite a bit of time, plus one final loud bang, there’s an announcement.
“THE ELECTRIC PLANT IS IN A NORMAL FULL POWER LINE-UP!”
Ah, both turbine generator sets are online now. More announcements are made, and then all hands not on watch have to help the electricians like Hash Brown divorce from shore power. My god are those three giant cables heavy! They look like long black fire hoses and need to be dragged out of the aft escape trunk, over one of the brows, to the pier and neatly stored. Sure, they may look like black fire hoses, but they’re not filled with water. They’re filled with copper! So picking up one of those cables is like picking up nine fully charged fire hoses at once. They’re unwieldy, and wrestling those beasts is a miserable experience. If I hadn’t been standing an Under Instruction watch with Jay-Jay, I’d be helping Hash Brown manhandle those shore power anacondas. That was my absolute least favorite workout in the Navy.
Now close to two hours into the startup, there were periodic short, roaring bursts of steam. Back in Shaft Alley, you can see the shaft rotate slightly, alternating directions each time you hear a burst. We’re at the tail end of Operating Instruction 27, and they’re warming up the main engines. Almost done now. The coners should be filtering on board getting ready to take us out. We wait back aft, now quite bored once again. Hopefully soon, the second R114 air conditioning plant I had just started up will begin to wrest our humid atmosphere back into something resembling a cool, habitable environment.
Eventually a bit of movement is felt. A tug is taking the sub away from the pier. Once free of the tug, we’ll be transiting on the surface for a while, maybe a few hours until the ocean is deep enough for us to dive with a comfortable margin below our keel. Well, we technically didn’t have a keel, but we still called it “depth to keel” anyhow.
There is a thing about a nuclear submarine on the surface to take note of. These boats are perfectly cylindrical, which is an unfortunate shape for those susceptible to motion sickness. Surface vessels—otherwise known as targets to us submariners—have V-shaped hulls resulting in a fairly predictable rocking motion. They sway side-to-side, accelerating towards one direction, slowing down and gently moving back the other way, accelerating again and then slowing down again for another reversal like a pendulum. It’s fairly rhythmic, and thus easy to compensate for while walking down a passageway. Not so inside my nuclear powered sewer tube.
The movement of a submarine on the surface in rough seas is chaotic. It can roll suddenly, then when it slows down, sometimes it will reverse direction just like a target, but sometimes it will fool you and accelerate in the same direction again. Psyche! And then it will suddenly snap back. Whoa! Best to walk with your hands out as it is totally unpredictable and sudden. Your face will eat a bulkhead if you don’t. I’m not sure what’s worse for seasickness actually. Rhythmic action or violent, unpredictable rocking. I’m not sure because I have never experienced motion sickness in the entire time of my enlistment. I’m apparently not susceptible to it.
Each hour, Jay-Jay and I would do a round in this crazy rocking and rolling sewer tube. I would be carrying a clipboard with about five pages of logs. There were hundreds of pressure, temperature, level and flow gauges to capture readings from and record in the logs. We had brought the ship to life, our reactor was critical, and it was now our job to monitor our specific section of it as we were now underway. Or more historically, stated this way:
“Underway on nuclear power!”
Those words were first transmitted from the USS Nautilus (SSN-571) by Commander Eugene Wilkinson on January 17th, 1955. There was less fanfare aboard the USS San Francisco (SSN-711) forty-three years later as we got underway. In fact, I liked to think that being underway on nuclear power in a much less flattering light, saying this was our dubious flirtation with fission. That was a term I picked up from the cinema as a youth.
I was ten years old when Star Trek IV came out. It’s the one with time travel to 1980’s San Francisco, humpback whales and the ghetto-blasting punk on the bus who people cheered about when he was, for all they knew, killed by Spock right in front of their eyes.
Note to self: don’t mess around with scorned mass transit utilizing San Franciscans!
Anyway, I loved that movie and became a huge fan of Star Trek precisely because of it. Spock, however, was not exactly a huge fan of the method of propulsion aboard the USS San Francisco, and said so while in San Francisco:
SPOCK: If memory serves, there was a dubious flirtation with nuclear fission reactors, resulting in toxic side effects. By the beginning of the fusion era, these reactors had been replaced, but at this time, we may be able to find some.
KIRK: I thought you said they were toxic.
SPOCK: We could construct a device to collect their high-energy photons safely. These photons could then be injected into the dilithium chamber, causing crystalline restructure… theoretically.
KIRK: Where would we find these reactors… theoretically?
SPOCK: Nuclear power was widely used in naval vessels.
Well, here I was out to sea on my twentieth century naval vessel, emitting our high-energy photons from our critical reactor away from port for a couple of weeks. Now, just like how you now know that a “critical” reactor is no big deal in real life when compared to the Star Trek cinematic universe, we should probably talk about Spock’s plan to “collect photons” here.
What the hell is a photon? I didn’t cover that in my explanation of fission! Have I led you astray!?! No, I most certainly did not. There is no need to talk about photons in a basic explanation of fission. So, what is a photon? Okay, photons are electromagnetic waves and should not be confused with protons, which as you know are positively charged particles inside the nucleus of an atom. You know this, and you know their place in fission.
But do nuclear reactors have or make photons? Yes, they emit a lot of photons, which as I stated above are electromagnetic waves. It’s a form of radiation. In our case, the photons a fission reactor emits is gamma radiation. Now before you go running away from all photons, keep in mind that most are not harmful, and many are quite useful. An example of a useful photon? Visible light. That’s a very useful photon. Please don’t run away from it unless you’re in a coma. In that case, stay away from the light!
So, I have no idea how Spock’s photon collecting plan would work. Collecting gammas (the highest energy form of photon) is not unlike saying you’re going to collect light (a much lower energy form of photon). Guess I’d have to attend Starfleet Warp Propulsion School to understand. Wonder how long their Peepahleenay is. Or will be, I guess.
That’s too far in the future to worry about however. Jay-Jay and I were merely concerned with the very near future, where we would be getting off of watch, grabbing a bite to eat, taking a shower, and hitting the rack. Also in the very near future, we would be submerging, and that would settle out all the damn rocking and rolling we were experiencing. Once submerged, we could settle into our underway routine as well.
My routine would include a few more of these Under Instruction watches before I could go for my interviews with Queen La Chiefa, then my division officer, and finally the Engineer. After passing my interviews, I would be fully qualified as an Engine Room Lower Level watch stander, with no need for Jay-Jay to keep an eye on me. He would then move up to Engine Room Upper Level. He was already qualified for that station. The senior Engine Room Upper Level watch stander would then bump up to Engine Room Supervisor. The senior Engine Room Supervisor could then move up to Engineering Watch Supervisor. That’s the natural progression for us mechanics back aft.
This two-week period out to sea was strictly for that sort of training. We were beginning our work up for a six-month deployment called a WESTPAC. That’s another Navy portmanteau, and it stands for Western Pacific. From this point on, we would go out to sea just about every other week to train for two intense evaluations that the Navy would conduit prior to the big deployment.
One evaluation was called an ORSE, which rhymes with horse, and the other was called a TRE, in which the letters are said individually. The former was for the nukes (Operational Reactor Safeguard Examination), while the latter was for the coners (Tactical Readiness Examination). But I wasn’t thinking about any of those evaluations while doing my rounds and taking logs, waiting to submerge. I was thinking about getting back to port. Queen La Chiefa said we’d be back by Christmas, which marked 1133 days to go for me. I could go then to the nudie bar for some Double Black Stout, see the naked ladies, and have a little dubious flirtation of my own.
_________________________________________________________________________
COPYRIGHT © 2023 FULLOFSEAMEN.COM
ALL RIGHTS RESERVED
(THIS INCLUDES THE RIGHT TO POST NAKED PHOTOS OF YOU ON THE INTERNET IF YOU USE MY MATERIAL WITHOUT PERMISSION.)
I think it’s interesting so far but I have a difficult time with physics.
I think it’s interesting so far but I have a difficult time with physics.