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For those with access to a university library, the Annual Review of Earth and Planetary Sciences has an interesting review by R. Scott Kemp on environmental detection of nuclear weapons programs. The surprising finding of the piece is that technical means are probably further advanced than we think, but that they are expensive and have not yet been deployed.
The good news for such efforts is that there are still only two main cost-effective fissile materials—plutonium and enriched uranium—and the feasible ways of getting there for each are well understood. The result is that detection can be achieved if it is possible to identify all the technologies generating precursors, or all technologies in the two functional steps in separation and one of the two functional steps in the transmutation process.
Costs come in part from the fact that detection of these processes must occur at some distance from an uncooperative state, requiring networks of multiple sensors (and cooperation from neighboring states, not a slam-dunk with respect to either Iran or North Korea). The article then walks through these possible technical means for detecting uranium mining and concentration (hyperspectral imaging and chemical detection); conversion, both centrifuge, laser and chemical separation; and transmutation (in reactors, reprocessing and even accelerators).
The conclusion is particularly interesting for North Korea because of the difficulty of detecting a possible second enrichment site in addition to Yongbyon; the presence of such a site has been a recurring reason why some analysts believe a freeze is pointless. Kemp concludes that a tight global detection web is infeasible for the time being, but that investment in a limited intelligence-gathering capacity targeted at specific states or regions could pass a cost-benefit test. Technical means remain a crucial part of the IAEA regime, and with respect to both Iran and North Korea. We still need some political means for slowing a program, but given the concerns about the two main nuclear headaches, seed investment in these technologies may be warranted.
