The Atomic Bomb – From Function to Fallout


I was invited to speak on 6 August 2017 at a special event hosted by the Congolese Civil Society at the Iziko South African Museum in Cape Town, South Africa. The conference was to be on nuclear weapons, the bombings of Hiroshima and Nagasaki, the legacy of atomic weapons and how the Congo was directly involved in the acquisition of uranium for the bombs dropped on the two Japanese cities at the end of World War II with the small mining town, Shinkolobwe, being the epicentre of the uranium mining. And yet, the world knows practically nothing bout this, assuming the uranium came from elsewhere – which is a typical mindset of the time as many saw Africa purely as a resource hub and not a land unto it’s own.

To learn more about the Shinkolobwe mines and how they related to WW2, Africa, Uranium and the CIA check out Spies in the Congo by Susan Williams and this article on Al Jazeera.

At the conference, I was asked to talk on the scientific aspects of atomic weaponry, and specifically the functions of Little Boy and Fat Man (dropped on Hiroshima and Nagasaki respectively), and the fallout of such detonations, so that those in attendance could understand, not only the human cost of nuclear weaponry, but also the mechanisms behind this very real, and very present threat to contemporary life. With North Korea getting bolder and more aggressive with their nuclear weapons threats and tests, and with a nuclear power such as the US currently being governed by a petulant man-child, not since the height of the Cold War has the world been so close to nuclear war.

It needs to be stated that I am not a nuclear scientist or an atomic weapons expert – I am a historian. However, a significant part of my studies of the Cold War (my specialist field of study) has been on the development and effects of nuclear weaponry, not only on a socio-economic level and not only with regards to the human and environmental impacts, but in terms of their mechanisms and the physics behind the most powerful weapons humanity has yet devised.

With that in mind, I presented the below to the conference entitled Shinkolobwe Hiroshima: “The Missing Link” Phase III. I will post links to the conference topics and video of the event once I have them in hand.


Full conference video can be found here:


A world war means exactly that; a war involving the entire world, and the effects from events between 1939 and 1945 are still being felt today, across continents and cultures, whether they realise it or not. One of the biggest and most important developments to pour from the gaping wound of World War II would be the development of the Atomic Bomb and subsequently atomic, or nuclear, energy. The natural consequence of war is a filling of the power vacuum left by warring powers and in the case of WWII, the US and USSR were those who stepped in to fill the gap left by the devastation done to the European powers and their colonies. The Cold War was filled with tension on a global scale, across many geo-political fronts, but a more insidious fear overshadowed all the rest: the threat of nuclear extermination. This arose from what humanity witnessed at the nuclear bombings of Japan and the horrors of that legacy have informed all nuclear policies to this day. The events at Nagasaki and Hiroshima represent the first and last times nuclear weapons have ever been deployed in war, and hopefully we shall never see their like again. By extension, all of us are children of World War II and subsequently the Cold War.

Cold War

It seems absurd that something as small as an atom could potentially dictate the fates of millions, but then we have seen similar tiny and supposedly inconsequential presences almost annihilate humanity before, as in the case of the Black Death for instance, which dropped worldwide human populations by over 75 million. And yet, the potential power contained within an atom, both usable for good and evil, is remarkable to say the least.


There is, of course, much in the way of technical information describing not only the research that lead to the discovery and development of atomic power, but also the actual process of nuclear fission and detonation of a nuclear-yield weapon. However, this article is meant to be brief and so I will stick to the most relevant information with regards to the Nagasaki and Hiroshima bombs.

Thermonuclear oubliette
Courtesy of Freestyle Illustration for Depthcore

gun type vs implosion

The two bombs dropped on Japan during World War II were of differing designs. To ensure the first bomb didn’t detonate whilst still in the hands of its wielders, the two pieces of the uranium core used for the primary detonation are separated by a metal wall and a conventional explosive, such as TNT, is used to crash the two pieces together at the right moment and create the chain reaction which leads to the detonation. This is called a gun-type assembly method. The Little Boy bomb dropped on Hiroshima made use of this method, whereas the Fat Man bomb dropped on Nagasaki made use of plutonium and an implosion type assembly which meant the plutonium core was bombarded at the right moment, again with conventional chemical explosives, to produce the desired chain reaction.

“Fat Man”, implosion type, dropped on Nagasaki
“Little Boy”, gun type, dropped on Hiroshima

Or, put another way:

the symbols

Most of us are familiar with the basic diagram of the atom, we have seen it throughout popular culture and many schools have it as part of their science class curriculum. Likewise, the infamous mushroom cloud created by a nuclear detonation as well as the international hazard symbol for radiation is very prevalent in society, but few know the actual mechanisms and historical context behind these now popular symbols.

The international hazard symbol for radiation

The symbol was first created in 1946 to represent the presence of harmful Ionizing Radiation. The full name of the symbol is the Ionizing radiation trefoil warning symbol (trefoil from the French word denoting a three-fold shape, referring to the design).

The original version was pink on a magenta background before changing to the more palatable colours we are now familiar with.

File:Radioactive Symbol 1946.svg
Original 1946 version

Read more the international radiation hazard symbol here.

Generic atomic planetary model

This familiar model of the atom, with orbiting electrons and protons, is based off of the Rutherford Model of atomic volume and is named after it’s creator Ernest Rutherford. The symbol was created in 1909 and appealed to the public imagination of the time and has since not only become a standard diagram used in schools worldwide, but also the logo of many institutions and the recognised symbol of atomic energy.

Though the model is not entirely accurate, but rather a simplified version of atomic activity and structure, it is still widely accepted as a stepping stone to further atomic understanding.

Read more on the atomic symbol here.

The infamous mushroom cloud

Whereas the mushroom cloud is not a specific symbol designed by humans, like the previous two, it has become a symbol unto it’s own as one of ultimate destruction and power. Though many other explosions also generate a mushroom cloud of sorts, or similar effect, including volcanic explosions, the atomic mushroom cloud, or pyrocumulus, is far more distinct and symbolic of what humanity is capable of.

Read more on the pyrocumulus here.



ground, air and water bursts

Before we get into the nitty gritty of atomic detonation, let us take a look at what the actual result of a nuclear detonation would be and specifically the bombs used on Hiroshima and Nagasaki. It should be noted that some nuclear bombs are meant for airburst or ground-burst – that is to say the detonation is meant to happen in the air, above a target, or on impact with the ground.

Ground Burst


Generally speaking, a ground-burst would be used to destroy hardened structures such as bunkers, missile silos, docks, etc. Such a detonation would cause much more debris to be sucked up into the mushroom cloud. This debris then becomes radioactive and produces fallout. As the detonation takes place at ground level, many structures shield one-another so the damage to above ground structures is less than in the case of an air burst.

Nuclear Destruction - Imgur



An airburst is used to destroy soft, above ground, targets, such as infrastructure and, yes, civilians and their homes. By detonating the weapon in the air at optimum altitude (which is dependent on the yield of the weapon), you can destroy more above ground structures as they are not efficient in shielding one-another from the effects. Less debris is sucked up by the mushroom cloud thus producing less fallout but more initial damage is done.



A water burst has not ever been used in warfare but has rather been used in tests to not only determine the effects of nuclear weaponry on or underneath the ocean, but to determine the voracity of a nuclear strike on a navy.

And incredible collection of recently declassified footage of nuclear weapons tests is available here.

The intention behind the Nagasaki and Hiroshima bombs were to cause as much damage as possible. The cities were considered legitimate military targets, but the nature of a nuclear weapon is such that civilian casualties are inevitable and it is arguable that this was the intended outcome as regular bombing of civilian targets had become a mainstay of WWII by this time. In order to make Imperial Japan surrender, the US wanted maximum damage and an airbust would accomplish that whilst ensuring less fallout. So, the lessor of two huge evils…slightly.

The actual death toll, though, was anything but lessened…

‘Little Boy’, 15kt, dropped on Hiroshima, – 146,000 dead or injured

‘Fat Man’, 21kt, dropped on Nagasaki – 80,000 dead or inured

Even so, actually visualising what such damage can do to a city is almost unfathomable to the human mind. Luckily, there exists and incredibly useful website for bringing this just a little closer to home. You can get a good sense of the scale of destruction from this program and hopefully gain a little insight into why these weapons are so terrifying. If you feel brave enough, take a look and see what could happen to your town.

My own country did not fair too well when I dropped the Tsar Bomba, the largest and most destructive bomb ever created, on Cape Town… The 3 million dead is just within the first few minutes of the detonation…



the process

In terms of the atomic process leading to the actual detonation, I will make it quick and easy to understand. In principle it’s simple – get some radioactive material to reach critical mass, sit back and watch the runaway nuclear reaction reach its target.

But in a more detailed explanation, enriched uranium or plutonium is needed to create the actual fission reaction which leads to the chain reaction which causes the detonation. Plutonium is a type of enriched uranium which is refined from mined uranium of which the Democratic Republic of Congo (then Belgian Congo) was a principle supplier.

Uranium 235 is the uranium most desirable for a nuclear reaction as it is the only uranium type whose atoms will forcibly split when neutrons are fired at it. When the nucleus of an atom in this refined uranium is bombarded with neutrons it breaks apart, shooting out energy and more neutrons, which can then hit and split other atoms. Get enough atoms splitting and you have the chain reaction needed for a bomb blast. This process is called Nuclear Fission. Just splitting one atom is not enough, a chain reaction of splits is needed in order to ensure  sizeable explosion.


the pyrocumulus


The mushroom cloud one sees after an explosion is created by the force of the explosion generating a fireball which sucks hot air into itself up a central column that then balloons and billows outwards. Cold air on the outside of the column helps push the column upwards where it then mingles with the hot air forming the distinctive top of the mushroom formation.



This formation can also be responsible for spreading radioactive fallout and creating black rain – radioactive rain spread over a wide area – depending on how much water is sucked up by the cloud.

The processes can be lengthy and detailed but I’ll move on to the true terror of the nuclear weapon: fallout.




Fallout is the term given to the irradiated debris and material deposited over a wide area after a nuclear detonation. It is also the term given to the general aftereffects of such a detonation in terms of lingering radiation in plants, soil, water etc, potential seismic instability, as well as the physical and emotional toll on human and animal life. The bombing itself is highly destructive, but a fallout cloud can reach kilometres into the atmosphere and cover a much wider range depending on the wind. Entire continents could potentially be affected depending on the bomb yield.

Since 1945, nuclear weapons have also been refined and perfected to the point where an aspiring terrorist could fit a small nuclear device in a suit case and detonate it in a crowded area. These so-called “dirty bombs” would be crude in design and thus would use lower-grade uranium which would increase the potential radiation fallout which would cause more damage over a longer time than the initial bomb blast.

In Hiroshima and Nagasaki the damage was immediate, but the fallout included widespread fires, destruction and damage to infrastructure, including emergency and health services, a disruption to water and food supplies, leading to disease and death, not to mention the emotional trauma from such a massive, and unexpected, on a civilian population centre. The physical trauma of blindness, burns, injuries were immediate, but radiation sickness would only become apparent several hours later and would lead to painful and unavoidable deaths. Some would only die days or weeks later and others would only feel these effects many months later after giving birth to stillborn or mutated children. Horrific does not begin to describe the cost of using these weapons and the ecological damage is still being assessed as radiation can remain in the soil for decades depending on yield and the type of burst used. Thankfully, radiation levels in Nagasaki and Hiroshima are back to acceptable background radiation levels in keeping with the world standard.

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In the end, peace.

Writing this article genuinely exhausted me. It’s difficult to retain a historian’s expected objectivity when the reality of what such a weapon can do is there in black and white, staring at you from across a roaring void of time but no less impactful.

I can only hope that this article, and others like it, truly help you, the reader, gain perspective on the serious realities of such warfare and weaponry. It’s not just the human cost, the environmental damage is staggering, and yet these weapons still exist today, against all reason.

I urge you to arm yourself with knowledge and resist your governments efforts to host these weapons. Learn their history and origins and put pressure on your leaders to do away with them for the sake of a more peaceful world.


A plaque adorns the Peace Statue in Nagasaki and is titled “Words from the Sculptor”.

It reads:

After experiencing that nightmarish war,

that blood-curdling carnage,

that unendurable horror,

Who could walk away without praying for peace?

This statue was created as a signpost in the struggle for global harmony.

Standing ten meters tall,

it conveys the profundity of knowledge and

the beauty of health and virility.

The right hand points to the atomic bomb,

the left hand points to peace,

and the face prays deeply for the victims of war.

Transcending the barriers of race

and evoking the qualities of Buddha and Go,

it is a symbol of the greatest determination

ever known in the history of Nagasaki

and the highest hope of all mankind.


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