Jump to content
  • entries
  • comments
  • views

How about that nuclear fission and fusion?



I am really good about managing my time and blogging, as you can see...

But I figured I would talk about the physics behind... BOMBS!!! I mean, nuclear warfare (at least in theory) has become every-so-popular after the Manhattan Project in the United States for World War II. I figured it is only fair to address it for all the physics glory it deserves.

Now, nuclear bombs can be split into two categories: bombs based on nuclear fission, and bombs based on nuclear fusion. However, both involve some sort of nuclear fission reaction at some point in the progress of the chain reaction (since that is all bombs are... one big, fun chain reaction!).

First, lets address nuclear fission bombs. Nuclear fission bombs can also be split into two subcategories: uranium bombs and plutonium bombs.

While U-238 is the most commonly occurring isotope of Uranium (92 protons, 146 neutrons), U-235 is the most valuable for nuclear weapons. On average, the fission of U-235 produces about 2.5 neutrons. A complete chain reaction of the fission of 50 kg of U-235, the approximate amount of Uranium in the bomb dropped on Hiroshima, could yield 500 kilotons of fissioned material. However, only 3% of that yield was achieved, given that most of the U-235 was dispersed in such a way that was spread to thin to continue the reaction. In order for the chain reaction to begin, the U-235 must reach a critical mass density. This is done by splitting such a critical mass of U-235 in half and placing each half on one end of the bomb. Then, when the bomb is ignited, half of the Uranium is shot like a bullet toward the other, creating a chain reaction, and therefore a nuclear explosion!

A plutonium fission bomb works in a similar manner, using Pu-239 instead. However, a plutonium bomb is harder to ignite. The plutonium is modelled like a spherical core, the "plutonium pit", and placed in a shell of high explosives. When the explosives all detonate at the precise time, it forms a spherical shock wave, which creates such an extreme pressure that the plutonium core is compressed to critical mass density and begins its chain reaction. Plutonium bombs are preferred, once mastered, since only 10 kg of plutonium is necessary for a reaction.

For fusion bombs, the hydrogen bomb is the name of the game. In order to begin the fusion reaction in a hydrogen bomb, a fission bomb needs to take place first in order to generate the high energy needed for hydrogen fusion. While normal hydrogen contains one proton, Deuterium is hydrogen which contains one proton and one neutron, and is preferred for a hydrogen fusion reaction. In a fusion reaction, deuterium and tritium, hydrogen with 1 proton and 2 neutrons, combine to create helium, a neutron, and energy. This causes lithium, also in the bomb, to combine with that neutron and create helium and more tritium and energy. This creates a chain reaction of creation and massive amounts of energy. When the warhead, a plutonium core fission bomb, is ignited in a fusion bomb, the fission emits x-rays, which reflects along the inside of the casing around the material for the fusion reaction, turning polystyrene foam into plasma, sparking another plutonium fission reaction. As the lithium deuteride is heated and compressed, it reaches the energy necessary for fusion, creating a massive explosion. This explosion is much more powerful than fission, creating massive amount of energy.

It's crazy that even as far back as World War II, scientists were investigating the physics around these nuclear phenomena and harnessing it for weaponry! What an amazing feat combining physics, chemistry, and technology!

Until next time, Fizzix Community, until next time.

  • Like 1


Recommended Comments

There are no comments to display.

Add a comment...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...