Anonymous asked in Science & MathematicsChemistry · 1 decade ago

What determines a nuclear bomb's megatonnage?

So I'm wondering, what determines the yeild on Atom/Hydro bomb?

They're all roughly the same size, so I figure it can't be the [i]size[/i] of the bomb. Perhaps the better concentration of critical mass in the bomb?

Basically I'm wondering what makes an 18 kiloton(18 thousand tons of tnt) so insignificant compared to something like the tsar bomba detonated by the soviets? Somewhere in the range of 57 megatons(57 million tons of tnt)

1 Answer

  • 1 decade ago
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    First, a nuclear weapon's yield is determined by the type of nuclear weapon it is. The three types are pure fission, fusion boosted fission, and two stage thermonuclear - each one more powerful than the last.

    Second, it is determined by how much plutonium is in the pit, or core of the weapon. This can be done by changing the mass of the pit, or the enrichment (concentration). It's important to understand here that plutonium pits are generally 90% enriched, so greater enrichment doesn't necessarily translate into that much more of an energy release. It's easier to use more plutonium.

    Early nuclear weapons were much larger than modern nuclear weapons, but this size difference actually belies their respective explosive power. The more modern, smaller weapons are far more powerful than the much larger older weapons. This is due primarily to improvements in weapons design. The motivation was to make the weapons smaller so more of them could be loaded onto a bomber, and so the missiles that deliver them didn't have to be as big.

    The bomb dropped on Hiroshima (Little Boy) was about one seventh of the mass of tsar bomba, but only about 1/3,000 times as powerful.

    Here's the difference: Little Boy was a pure fission weapon. Tsar bomba was a two stage thermonuclear weapon. To be sure, tsar bomba had much more plutonium, but this only begins to explain why it was so much more powerful.

    Also, two identical nuclear weapons can also explode with quite different explosive power. See the first link below.

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