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The nuclear bombs - Part 1
Today was the last session of my TPE (these are work to be done in a group during the year that allow us to get more points in the baccalaureate, it is necessary to successfully present a subject by answering a problem using two different subjects), and so I remembered a video of a TPE that I saw last year. The subject of the TPE in this group was the Little Boy and Fat Man nuclear bombs that had been used during the Second World War. This made me want to do a post on nuclear weapons, exposing different types of nuclear bombs, and trying to explain their operation quite simply.
The A bomb
First we will start with the A bomb because it is the first nuclear weapon created. What is an A bomb? First of all it is a nuclear weapon, so it creates energy (a lot of energy) following nuclear reactions. The energy obtained is generated by many nuclear fissions of atoms that are fissile. Now you are surely wondering what is a fissile atom?
Fissile atoms
In order for a fission chain reaction to take place in an atomic bomb and thus release a lot of energy, it is necessary to reach what is called critical mass. This critical mass is reached when the reaction can be self-maintained: when an atom undergoes a fission, it emits one or more neutrons which will subsequently strike other fissile atoms and so on. If a reaction produces just enough neutrons then it is said to have reached its critical mass, if it produces more electrons it is said that the mass is super critical. The critical mass depends on many different parameters to take into account: first the material, its density, its shape and its purity.
How a A bomb work
A bomb A produces an explosion thanks to the nuclear fissions caused by the chain reaction of a fissile material of mass on critical (3 times higher than the critical mass)
In order to prevent the bomb from exploding at any time and causing considerable damage, a mass of non-critical fissile material is needed, and then changes, pressure or shapes are made to reach a mass over critical:
- The first technique is the following: there are two subcritical masses of fissile material that are separated, when they are joined then the material will reach a (super) critical mass. To reunite them at the right time they are separated on either side of a bomb, with on one side a projectile and on the other a target, the projectile is a uranium cylinder propelled by an explosive or moment of the detonation, it is lodged in the target (where a space is present to accommodate the projectile). By coming in contact both sides reach their critical mass and the chain reaction begins thus creating the explosion. This first system was used for Little Boy, the bomb of Hiroshima, it is called assembly by insertion.
- The second assembly I'm going to talk about is the implosion assembly, it's the assembly used for Nagasaki's Fat Man bomb but also for the first atomic bomb in history, Gadget. The technique is quite simple to explain but quite complicated to implement: here, so that the material reaches a mass on critical it is compressed in order to increase this density. For this purpose we use explosives inside the bomb (hence the name) that must be triggered synchronously to create a spherical shock wave retracting on the fissile material. This technique makes it possible to reach a supercritical configuration (and thus trigger the explosion) much more quickly than with an insertion assembly, and much safer, which is why the bombs whose configuration is this one are most of the time made with Plutonium 239 as fissile material (because it allows to obtain a larger explosion since the fission of the latter produces more energy).
Now you know enough about bomb A and how it works, so I'll now tell you its story: why was it developed, by whom, how?
History of the A bomb
A- The Manhattan projet
To tell you about the history of Bomb A I must tell you about the Manhattan project, it's the code name of a US research project on the application of nuclear weapons. This project was created during the Second World War by President Franklin Delano Roosevelt following the letter Einstein-Szilard.
This letter was written by Albert Einstein and 3 nuclear physicists (Leo Szilard, Edward Teller, and Eugene Wigner) who persuaded Einstein to warn the US president that nuclear energy could be used by Nazi Germany to create nuclear weapons. bombs (atomic bombs so). A sum of money is released to study if such bombs were possible. After a few years it was shown that such a bomb was conceivable and so in 1943, 2 billion dollars are released to achieve in a Top Secret project what will become the first nuclear bombs. During this project many laboratories are created throughout the United States and even in the United Kingdom and Canada. The best-known laboratory is LANL (Los Alamos National Laboratory); This laboratory is run by Oppenheimer who works in cooperation with Niels Bohr, Enrico Fermi, Jack Chadwick and Isidor Isaac Rabi, these 4 physicists had obtained Nobel Prizes in physics. Two branches of research were created in this laboratory: one branch for an Uranium bomb and another for a Plutonium bomb (Atom discovered during research of the Pre-Project Research Project Manhattan). As a result of these two areas of research, three bombs were created: Little Boy, the only uranium bomb created during the project and to be dropped on the City of Hiroshima. Gadget, the plutonium bomb that will serve as a test and will be the first nuclear bomb to explode. And Fat Man the second Plutonium bomb that will explode on Nagasaki.
B- Uses of the nuclear bombs
Following the Manhattan Project, the Little Boy and Fat Man bombs were the first atomic bombs used in a War (and the only ones (hi, Kim-Jong Un).
They allowed the surrender of Japan at the end of the Second World War. Following the devastating effects of its bombs many states have wanted to acquire the nuclear weapon, so began a race for nuclear weapons, making the USSR, the United Kingdom, France, China and the United States. South Africa and Israel from the nuclear powers. Following this influx of weapons, the Nuclear Non-Proliferation Treaty was ratified in 1968 to avoid a possible Nuclear War that would destroy the planet. Following these decisions the atomic bomb became a weapon of deterrence especially during the Cold War the fear of the use of nuclear weapons by the enemy country prevent the direct attacks of the countries. Currently the nuclear weapon is the weapon with the lowest rate of direct use in a War since this weapon has been used only 2 times and currently many countries have it.
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