NuclearFission

Nuclear Fission

Nuclear Fission Basics

The first nuclear bombs underwent induced nuclear fission. Uranium-235 was commonly used to create this explosion, because it becomes very unstable easily. Fission happens because an element or isotope, like Uranium-235 that is commonly stable comes across a stray slow moving neutron. This neutron runs into the nucleus and is sucked up into the atom immediately. This causes and unbalancing in the nucleus and it splits almost instantaneously. This releases two new atoms and some neutrons, the amount is based on how the original atom split. The two new atoms then start to decompose and emit gamma radiation as the atoms start to adjust to their new forms. This process is almost exactly like how nuclear power works except for fission in a nuclear power facility happens on a smaller scale than on a nuclear fission bomb.

Interesting Facts

	The probability of a U-235 atom sucking up a neutron while it is going on its way is extremely high
	Unlike a nuclear reactor this fission process is uncontrolled to a degree, until the U-235 runs out
	In the properly working fission bomb the fission reaction happens more than once, once the first reaction takes place the new neutrons then go and are sucked up by another U-235 causing more neutrons to appear and so on...This is known as super criticality.
	It takes an U-235 atom Pico seconds (1*10E-12 seconds) to do this process of fission
	The products of the fission reaction weigh less than the original atom, this is because most of the mass is converted into an enormous amount of energy through the equation e=mc²

In a fission bomb to make sure that a premature reaction does not occur, the fuel is kept in separate sub critical masses (critical mass is the least amount of an element that will support fission).

The Problems that Appear with the Separation of the Fuel in the Design of the Fission Bomb

Two or more of the separated subcritical masses must be combined to make the supercritical mass which is necessary for fission to occur.

Loose neutrons must be introduced into the supercritical mass.

As much of the supercritical mass must be fissioned before the bomb explodes.

Problems Solved
The first problem is solved the invention of the Gun-Triggered Fission Bomb and the Implosion-Triggered Bomb. The first type fires a subcritical mass into another one, the second bomb type uses implosion to make the subcritical masses combine.

To solve the neutron problem a neutron generator is put into the bombs construction, which is a small pellet of polonium and beryllium, separated by foil within the fissionable fuel core. When the foil is broken and the subcritical masses come together, the polonium spontaneously releases alpha particles. Which then these particles collide with beryllium-9 to produce beryllium-8 and free neutrons. These new neutrons then collide with the new supercritical mass and start the explosion.

To increase the fissioned part of the bomb, a tamper is put inside, made of uranium-238, which gets hot and expands because of the fissioning core. The expanding tamper puts pressure back on the core which slows the expansion and it also reflect neutrons back into the core to increase the efficiency of the fission reaction.

Fission Quiz

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