It is at least a 2 part analysis.
1) The presence of certain elements, including Strontium and other elements related to nuclear reactions, and
Can you cite the individual elements and also the amount found in the USGS dust sample analysis?
While you are at it, can you compare that data to a sample data of a nuclear reaction to prove your claim that a nuclear reaction happened in the WTC complex?
I mean, it is your claim. You should be able to produce the data needed to show proof of such.