Before I begin this discussion, I’m going to start with a statement that I should have made in part one. That is, I’m not a nuclear engineer. I’m not a scientist, or a national security expert, and I have no security clearance or access to top-secret information. What I do have is a very special set of skills…no, wait, that’s not it. What I do have is a lot of time. A lot of time in the last 12-14 months in which I have spent an inordinate amount of that time studying nuclear weapons.
Now, when I say that, I’m sure it conjures up images of me Googling “How does a nuclear bomb work?” then reading the Wikipedia page and spouting off as if I’m an expert.
I will say this, just so we’re clear: I’m not an expert in nuclear weapons. I’ve never touched one, or even seen one in real life for that matter. My knowledge comes from more than 300 hours spent studying nuclear weapons, on the internet, in books, and in scientific journals. I link to many of my sources in this blog with the highlighted words, which are clickable links. After the last article in this series, I’ll attach a bibliography with all of the sources I used.
Now, 300 hours is a lot of time, but it doesn’t make me a nuclear scientist. In fact, it likely took me that much time only because getting my brain to absorb and comprehend this material is rather difficult for me. I think the level of research I’ve done only just barely qualifies me to convey entry-level information about nuclear weapons, and to try to clear up what I think are widespread inaccuracies in the perception of what nuclear war with North Korea would look like.
So, here we go!
In my first post, I began with a premise that I feel many people have an unhealthy fear of nuclear weapons, and that that fear is grounded in a lack of knowledge as to exactly what they are and what they do. I also stated that I thought people certainly had an unhealthy fear of the nuclear weapons that North Korea – the DPRK – has likely managed to build.
Now, just to be crystal clear, I don’t expect people to have no fear of nuclear weapons. I just think that most of the population has an unhealthy fear of them, and that fear comes from a lack of understanding as to just what they are, how they work, and what they do. I think of it as a monster under the bed sort of thing…we inordinately fear them because we don’t understand them. That premise is based on the fact that there is a vast difference in the types of nuclear weapons that the DPRK has, and the type currently owned by other nations such as the United States, Russia, and China.
When we created the first atomic weapons, nobody outside the scientists and engineers and a few people in the government and the military knew what they were. Although tens of thousands of people were involved, only a handful of them knew all the details. It was top-secret code word stuff. Most people today are familiar with the Manhattan Project and the story behind the effort to create the first atomic weapon thanks to movies and a lot of great documentaries. We all know that it was the British who really made the first strides toward creating the bomb, and the combination of the efforts between the U.S. and Great Britain that eventually led to Trinity, the first ever testing of an atomic bomb.
I’ll spare you the details of the problems that were encountered just in the isolating of the correct isotopes, first of uranium, and later of plutonium, not to mention the engineering difficulties that were encountered with 1940s technology, but let’s just say, they were extensive. Naturally occurring uranium is mostly uranium-238, and within that mined uranium ore exists a very small percentage of uranium-235, less than three-quarters of one percent to be exact. And uranium-235, known as highly enriched uranium, is what is needed to create fission, the catalyst behind the destructive power of a nuclear bomb. Separating it in the quantities needed to produce just one atomic weapon was a vast undertaking.
The other weapons-grade fissile material that could be used at the time was plutonium. Plutonium — both plutonium-239 and plutonium-240, could only be created in nuclear power plants, and, it turned out that plutonium-240 was too highly spontaneously fissile to be used in the original atomic bomb design. Like I said, lots of problems. Luckily, we had some of the world’s smartest scientists and engineers working on the problem.
Like J. Robert Oppenheimer, and nuclear fission was achieved. The first bomb created was tested in what became known as the Trinity Test.
The bomb detonated in the Trinity Test was nicknamed The Gadget, and it was detonated in New Mexico at Alamogordo (now part of the White Sands Missile Range.) It was an implosion-type plutonium bomb, of the same design as the bomb which was eventually dropped on Nagasaki, and completely different than the originally planned device which was a projectile fired design like the type dropped on Hiroshima. More on these types later.
The test was conducted at 5:29am on July 16, 1945. The first ever detonation of an atomic bomb was on U.S. soil, and it was an unequivocal success.
Here’s a picture of the explosion taken by Berlyn Brixner at sixteen thousandths of a second after the explosion.
The top of that spherical shockwave reaches about 500 feet high. Sixteen thousandths of a second after detonation. Incredible.
Before we discuss the blast yield of The Gadget, let’s talk about what blast yield actually means.
Blast yield for explosions is usually measured in the equivalent amount of TNT that would generate the same explosive force. TNT is short for trinitrotoluene, and it’s created from a mixture of various chemical compounds. It’s slightly less powerful, and NOT the same thing as dynamite, despite what I was led to believe from early childhood.
When we’re talking about nuclear-quality explosions, blast yield is measured in metric tons of TNT. A metric ton is 1000 kilograms, or about 2200 pounds. So, a blast yield of one ton would be the same as the blast that would be created by 2200 pounds of TNT.
A kiloton is 1000 metric tons. 1000 tons multiplied by 2200 pounds per ton means that an explosion measured at one kiloton of blast yield would be the equivalent of blowing up 2.2 million pounds of TNT. That’s a lot.
A megaton would be one million metric tons of TNT. Expressed in pounds, that’s the equivalent of…well, a ton. Lots of tons actually. I don’t want to get into these kind of ridiculous numbers yet, but we will later.
So, anyway, one kiloton would be a massive explosion. At the time of the Trinity test, the largest man-made explosion had been the maritime accident known as the Halifax Explosion on December 6, 1917. If you’ve never heard of it, it’s an incredible story. We know the blast yield of the Halifax Explosion because we know exactly what blew up – 2900 tons of TNT, making the blast yield around 2.9 kilotons. It resulted in approximately 2000 deaths and 9000 injuries.
If you were alive at the time and thought the Halifax Explosion was the mother of all explosions, the scientists at the Trinity test were about to ask you to hold their beers.
The Gadget detonated with a yield of approximately 20 kilotons. Seven times the Halifax Explosion. The equivalent of 20,000 metric tons of TNT, or 44 million pounds.
Eventually, we’re going to discuss the radiation exposure and fallout from this test, as well as the long-term effects it had on the test area, including what you can expect to find if you go right to ground zero today, but first, I want to talk about exactly how this bomb worked.
I mentioned earlier that it was an implosion-type plutonium bomb, and it was different from the original conceived model which was a gun-type fission uranium bomb. Since it was so difficult to extract uranium-235 from the natural uranium-238, and since they’d managed to enrich only enough uranium for one bomb at that time, they’d reverted to the plutonium bomb for the test.
As I mentioned earlier, plutonium is created in nuclear reactors. The plutonium for The Gadget, and the other bombs of that time, was all created at Hanford in Washington State.
The main difference between the gun-type bomb and the implosion-type bomb, other than the fissile material used, is the way in which the fission reaction is instigated. Uranium-235, plutonium-239, and plutonium-240 all have the ability to go super-critical under the right conditions: generally meaning when they are compressed or when they are slammed together at high speeds. This gives us the two earliest types of atomic bombs.
A gun-type fission bomb is about the simplest type of atomic bomb out there. It’s also the type of bomb we dropped on Hiroshima, the one known as Little Boy. It’s regarded as one of the highest risks for proliferation and terrorism because it’s so simple in design. If one has enough quantity of uranium-235, they can create a gun-type bomb with little manufacturing or fine engineering.
A gun-type bomb takes one slug of uranium-235 and fires it, using conventional explosives or propellants, into a target spike of the same material. The slamming together of the two chunks of uranium causes a critical mass, which results in nuclear fission, the splitting of the nucleus of an atom, which results in enormous releases of energy. And that’s it. That’s all it takes to make a nuclear explosion.
The science behind nuclear fission is too complex for my brain, despite the fact that I’ve spent dozens of hours trying to comprehend it, but the important part is, it causes a really big explosion as the fission works its way through the critical mass of the enriched uranium. All-in-all, the gun-type design is a very simple design, and quite dangerous as there are a number of ways the two chunks of enriched uranium could accidentally slam into each other (i.e., a crash of the airplane or vehicle hauling the bomb, or the striking of the ground in an accidental drop, or even the acceleration of a missile were you to try to mount this type of weapon on a missile) which could result in a nuclear explosion.
The other type, using explosive compression, is more complex, but necessary for both stability and safety, and for the use of plutonium as the fissile material. Because plutonium-239, when it’s created in a nuclear reactor, contains large amounts of plutonium-240, and because plutonium-240 is dangerously unstable and ready to go super-critical just from early triggering of the gun reaction, it can’t be used in a gun-type fission bomb. This is what led to the development of the implosion-type fission device, which is the type of bomb The Gadget, and Fat Man, the atomic bomb dropped on Nagasaki were.
In an implosion-type device, the fissile material is surrounded by carefully manufactured explosives in a sort of cocoon. (In modern designs, we use lenses, which we’ll discuss later.) Those explosives fire simultaneously, compressing the uranium or plutonium to two or three times its original density, which causes it to go supercritical and explode.
This type of device was the basis for all future nuclear weapons due to its versatility. The basic design of the implosion bomb is used for thermonuclear weapons, both single stage, and in the Teller-Ulam design, both of which we’ll discuss in great detail later on.
Approximately three weeks after the Trinity test, on August 6th, 1945, the Enola Gay, piloted by Colonel Paul Tibbets, dropped Little Boy, the first gun-type atomic bomb created, on the Japanese city of Hiroshima. The device had never been tested because the U.S. hadn’t produced enough enriched uranium to create more than one device, and because it was such a simple design, the scientists were convinced there was nothing that could really go wrong. And they were right. Little Boy detonated at an altitude of almost 2000 feet above the ground, and it was a tremendous success (depending on your perspective), creating an explosive yield of approximately 15 kilotons, only 75% of the yield of The Gadget, but enough to immediately kill an estimated 66,000 people, including 20,000 members of the Japanese Imperial Army.
The interesting thing about the yield is that it was very nearly a dud. In fact, there was 141 pounds of uranium-235 in the fused pit of the bomb, and only 2 pounds of that actually underwent fission and contributed to the yield. That’s less than 1.5% of the fissile material that actually went critical and exploded, and it created a 15-kiloton yield. The remaining 98.5% of the highly enriched uranium contributed nothing.
A couple of notes about Little Boy:
- The entire bomb weighed 9700 pounds, the majority of which was the weight of the casing.
- The blast detonation is spherical, thus the desire to detonate it at an altitude of 2000 feet — by doing that, you’re able to utilize the full effect of the spherical blast wave.
- It was determined that although the yield was the equivalent of 15,000 tons of TNT, the same destruction could have been realized by dropping just 2100 tons of conventional weapons, due to much of the spherical blast wave being wasted into the atmosphere and surrounding, sparsely populated areas.
- It would have taken 220 B-29 bombing runs consisting of various types of conventional bombs to achieve that 2100 tons and achieve the same effect as the one Little Boy weapon.
So, 66,000 people were killed right away. In fact, the total number of deaths in the first few months following the explosion is estimated in the 90,000 to 140,000 range. In order to take a look at exactly what killed all those people, we have to look at how a nuclear device of this type and era actually kills.
The initial causes of death are from the fireball, the over-pressure/blast wave, and from the radiation. In Hiroshima, almost everything in a three-quarter mile radius under the point of the explosion was immediately destroyed by the pressure wave and fireball. There were some reinforced concrete structures that remained standing, and interestingly, in one of them, just 560 feet from ground zero, a man survived the blast, as well as the aftereffects, living for decades after.
Other than that guy and a few other exceptions though, nearly all of the people within that three-quarter mile radius of ground zero were killed immediately. Later testing determined that an over-pressure blast wave of just 5 PSI will kill 100% of people in its path.
In Hiroshima, this blast wave destroyed nearly every building, most of which were made of wood or paper products. The explosive fireball touched off a massive firestorm which caused even more destruction, killing thousands more people, and destroying nearly all the homes and buildings in an area of nearly five square miles.
Let’s talk about radiation. Much of the lethal radiation produced by a nuclear explosion survives only for as long as the fireball – mere seconds. It’s known as initial radiation, and it’s mostly gamma and neutron radiation. This is bad radiation. The kind that kills you very quickly. However, for most people exposed to it, they’re being killed by the fireball and the over-pressure wave anyway, so it’s mostly irrelevant and redundant. Anybody lucky enough to survive the fireball and over-pressure though, will usually die from this lethal dose of radiation. In Hiroshima, the lethal dose radius was close to one mile, and many people were able to survive the blast wave in that radius. Most of those inside that one-mile radius who received that lethal dose died immediately after the blast in the firestorm that followed, unable to escape the flimsy wooden structures, and so the effects of the radiation were not actually realized. The firestorm was so powerful that it cremated the bodies and destroyed all evidence of their existence, (birth and residence records were destroyed as well) which makes accurate death figures impossible to determine.
After initial radiation, the next concern is residual radiation. One of the benefits to the high-altitude air-burst of the bomb, was the lack of nuclear fallout. Most of the fallout from a nuclear explosion is due to the contamination of particles from the ground soil. After the initial fireball expands, it then has to contract, and that causes a suction effect that sweeps everything up into it and pulls it into the air — becoming the iconic nuclear mushroom cloud.
When that happens near the ground, particles of soil are pulled into the soup and become irradiated. They’re lofted into the air where wind currents take them along for a while before dropping them again, causing the radiation to spread far and wide. Some mushroom clouds actually reach into the stratosphere where particles can remain sometimes for years, circling the planet before falling to earth. This actually ends up being a good thing as it spreads the radiation far and wide, depositing it in non-lethal doses around the globe.
The higher the air-blast, the less particles of soil that will be pulled into the radiation, and the less fallout there is. In the case of Hiroshima, with the air-blast at nearly 2000 feet of elevation, nuclear fallout was quite small. There was still that ~140 pounds of subcritical uranium, plus the ~9600 pounds of bomb casing material, plus particles that were in the air already, and so forth, but the amount of nuclear fallout was minor due to the absence of soil particles.
One of the most common misconceptions surrounding a nuclear explosion deals with the level of residual radiation at the blast site. Most people believe that blast sites are uninhabitable for decades or even centuries. In Hiroshima, it’s been shown that the only radiation deaths that occurred were people who were directly exposed to the bomb detonation itself. None of the aid workers, doctors, firefighters, or anybody else who entered the blast area after the bombing were killed or even injured by residual radiation. Don’t get me wrong, there was some measurable increased radiation in the bomb area, particularly in the first day or two after the explosion, but it dissipated rapidly and wasn’t significant enough to kill or injure anybody.
There weren’t any standing houses left within one mile of the bomb epicenter, but had there been, residents of Hiroshima could have moved back into their homes directly under the blast area just days after the firestorm subsided, and they would have lived without a dangerous increase in radiation exposure. In fact, many people today live in Hiroshima and in Nagasaki, and they have the same level of exposure to radiation as the rest of the general population.
This is not meant to trivialize the effects of the radiation. For those exposed to the bomb blast who didn’t die from the blast itself, the radiation levels were often deadly, killing many within the first 30 days after the explosion. Others died years later from various cancers, leukemia being the most prevalent. However, all of those who died from radiation illnesses were exposed to the bomb blast itself, and all were close to the epicenter of the blast.
The British Mission, which went to the sites of Hiroshima and Nagasaki to study the effects found that at three-quarters of a mile from the blast epicenter, the radiation survival rate was greater than 50%. At one mile and beyond it was more than 75%, and at two miles distance, there were some reports of radiation sickness, but no reported deaths, and the residual cancer rates were statistically the same as the rest of the world.
There were no higher incidents of cancers or other mortalities from any person not exposed to the actual bomb, nor from any person outside of two miles from the epicenter, nor from any person who entered the actual bomb area immediately after the explosion.
For many years, even decades, reports of birth defects from pregnant survivors were reported. They were all shown to be false. In 1985, Johns Hopkins University human geneticist and professor of genetics from the University of Wisconsin, James Crow, completed a study that confirmed the number of birth defects from survivors of both Hiroshima and Nagasaki was not significantly higher than those of the general population. A pregnant woman could have moved into a house directly under the epicenter of the bomb, a week after the explosion, and both her and the baby would have been fine.
I mention this because of the common misconception that nuclear bomb sites are uninhabitable for generations. I grew up with the misinformed teachings that nuclear sites are graveyards, with images of zombie children with three arms living in the green glow of Hiroshima for years after the bombing.
It’s just simply not true. Now, there are ways to use nukes to make a place uninhabitable, and we’ll discuss those later, but other than intentionally irradiating an area, simply detonated a nuclear weapon on a city does not leave lasting long-term radiation effects.
Three days after the Hiroshima bombing, with the Japanese still refusing to surrender, the U.S. dropped Fat Man onto the city of Nagasaki. Fat Man was a plutonium compression bomb, similar to The Gadget detonated in the Trinity test. The blast yield was also similar to The Gadget, at an estimated 20 kilotons of TNT. Because the bomb was dropped slightly off-target, and because hills confined the blast to one narrow valley the death toll was less than at Hiroshima, even though Fat Man was more powerful than Little Boy. Estimates for the death toll seem to vary widely due to poor record keeping, but it’s likely they were somewhere between 35,000 and 80,000 total deaths.
The Nagasaki bomb was the final straw for the Japanese, who quickly realized that more of their cities would be destroyed by this awesome technology in the coming days and weeks. Emperor Hirohito unofficially surrendered on August 14th, just a few days before the next bomb was due to be dropped.
Debates have raged for decades as to whether or not the bombs were necessary, and that argument is well beyond the scope of this blog, however, it’s important to note that the Japanese were not going to surrender anytime soon, and that, as mentioned above, it would have taken 220 successful B-29 bombing missions to equal the destruction and death achieved with one atomic bomb. Who knows how many unsuccessful missions it would have taken to achieve 220 successes, and how many Americans, Japanese, and other nationalities fighting would have died in the other Pacific theaters during that time, or if that drawn-out destruction would have even been an encouragement for Japan to surrender. It seems unlikely to me that it would have.
In the next blog in this series, I’ll briefly discuss atomic testing after the war, as well as the Cold War and the arms race, all in a lead-up to present-day thermonuclear weapons and the types of bombs that North Korea has likely achieved, as well as the effect of a nuclear attack by the DPRK on America, and the likely result of an American nuclear counter-attack.
Author Rick Fuller 
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