U.S. Prepares to Get Nuked

There's an important story in the NYT about new efforts from the U.S. national laboratories to retain and improve their ability to identify nuclear fallout. In a nutshell, any fissionable materials turned into a nuclear weapon will be composed of a specific ratio of various radionuclides, which form a sort of signature, which can be used to identify the source of the fissionable material. The problem is, naturally, that you're probably doing this after the detonation.