Nuclear fission, a process whereby a uranium nucleus absorbs a neutron, is not.

核裂变却是一个铀核吸收一个中子，而不是其它过程。

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Each fission reaction splits the nucleus of an atom of uranium-235 or plutonium-239 into two smaller atoms and releases a great deal of energy.

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Fusion is the process of forcing the nuclei of atoms so close together that they fuse into a nucleus of a new element. (Fission, of course, is the opposite: energy produced by splitting nuclei.) The new, fused nucleus weighs less than the original two.

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