Good point. I also agree with your point 3. To pick a nit here that may not be unimportant, was it the containers that tested for the presence of plutonium, or the contents? I can’t be sure from the Post story.

“Now, the Times story does trace the UF6 back to North Korea, but how reliable is the intelligence method the article describes (e.g. process of elimination, tracking U-234, etc.)? What kind of samples do you need from a country in order to make an identification? Is natural uranium enough, or do the samples need to come from uranium compounds (e.g. UF6?).”

The Times story points out the uncertainties. The process of elimination is the diciest. As I suggested at WhirledView, samples with U-234 content that doesn’t match country standards could have come from Soviet processing plants, where, say, Hungarian, Czechoslovak, and Kazakh ore might have been mixed together. If the uranium hasn’t been through a reactor or enrichment, the isotopic makeup remains unchanged.

I strongly disagree that “the two don’t seem to exclude one another.” For my argument on this, see the WV post. I find this the most interesting aspect of this story: For a change, the science in both stories is reported in a way that seems reasonably accurate, and not garbled versions of a single story.

One possible interpretation: two samples with different provenances were analyzed by two labs. The Times mentions Oak Ridge, but the Post doesn’t mention a specific laboratory.