# Einstein, Fusion and Fission

### Einstein, Fusion and Fission

Albert Einstein, a strong pacifist, didn't actually help build the atom bomb but his contributions to science made the bomb possible. Despite his aversion to war, Einsten encouraged President Roosevelt to build the bomb because feared that Germany was trying to build their own atomic bomb. E = MC^2 - Einstein's equation demonstrating that enormous amounts of energy can be generated by splitting atoms. E = energy, m = mass, c = speed of light in a vacuum. Speed of light is very large, so small amounts of matter can have enormous amounts of energy. Einstein was consulted once about the atomic bomb, about a theoretical problem relating to fission, which Einstein finished in two days.

There are currently two types of nuclear warheads: pure fission bombs, also known as or nuclear bombs, and fusion-fission bombs, also called thermonuclear bombs. "Atomic bomb" refers to pure fission bombs, and "Hydrogen bomb" refers to fusion-fission bombs.

### Fission Bomb

- Fission bombs explode when they reach critical mass. Critical mass is achieved there is enough fission in the uranium or plutonium core to cause a chain reaction. - K = f - I - F = ave. number of neutrons released per fission event - I = ave. number of neutrons lost

- Mass is critical when k = 1 - Fission must be kept at subcritical mass until detonation begins.

- Uranium is split up into several compartments so that there aren't enough fissile reactions to reach critical mass. - Fuel is either Uranium-235 or Plutonium-239. Both these isotopes must be synthesized from Uranium-238 - There are two ways to detonate a fission bomb. First method is called gun-type

- Simply shoot a little piece of uranium (or plutonium if it's a plutonium bomb) into the sphere at the velocity needed to start a chain reaction: - Both bombs dropped on Japan to end WWII were gun-type fission bombs. - Gun-type nuclear weapons are no longer in use, but during WWII this was the easiest method of detonation for uranium bombs. WWII-era plutonium bombs had to use implosion, though, because the casing would have had to be so long in order for the plutonium bullet to reach the necessary velocity that it was aerodynamically impossible. - Second method of detonation for a fission bomb is implosion

- Uranium or plutonium core is surrounded by detonators, which explode and direct pressure inward towards the core, compacting the subcritical masses into one critical mass so that there is enough fission to ignite the bomb. - The tamper is often made of beryllium oxide. It reflects neutrons back into the core while the uranium/plutonium is undergoing fission. - The implosion technique employed in modern implosion bombs has been modified. Now when the subcritical masses are brought together by the explosion of the detonators, they hit a piece of beryllium/polonium that is located in the very center of the core. Fission begins and the bomb explodes.

### Fusion Bomb

#### Pure fusion nuclear weapons

- Do not currently exist
- Would have to generate enough heat to fuse together deuterium and tritium, which so far has proved impossible outside of a lab setting.
- The biggest advantage would be much smaller amounts of nuclear fallout because uranium and plutonium, which are very radioactive, wouldn't be used.
- The downside is that pure fusion weapons would be much easier to build than fission-based nukes, and therefore more easily built by hostile nations, such as Iran.

#### Boosted fission weapon

- A fission bomb that uses fusion fuel to increase efficiency
- Has tritium and deuterium in the center of the sphere or between layers of the inner core.
- Only 1% of the uranium or plutonium needs to fission for enough heat to be generated to bring about thermonuclear fusion.
- Fusion can double the efficiency of a fission bomb

#### Carey Sublette, Nuclear Weapons Frequently Asked Questions

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