"Fingerprint" of nuclear materials ... true or false?

I have often heard—and had it reinforced by watching The Sum of All Fears—that the fissionable material in nuclear weapons has a kind of “fingerprint.” That, because of the differing levels of different isotopes resulting from different generation/processing facilities, you could tell where each warhead’s plutonium or uranium came from. To the degree of accuracy that you could sometimes even tell which reactor in a particular nuke plant produced the material, and in which month of which year—and that you do so just by analyzing the fallout/residue from a nuclear blast.

Is any of this true?

Can you, in fact, distinguish nuclear materials in such a way?

Can you do so just from the fallout/debris of an exploded nuke?

Is there some huge database (at the IAEA?) where every country and facility’s nuclear “fingerprints” are kept?

If all this is true, how difficult is it to analyze/match these fingerprints?

How long does it take?

What sort of equipment (gas chromatograph? mass spectrometer? something the size of a refrigerator? something the size of a breadbox?) do you need?

What sort of site samples do you need from the blast zone to make such an analysis?

You can tell specifically what kinds of radiation are given off by a source, and in what quantities. It is simple enough, therefore, to figure out exactly what radioactive elements are present in your particular sample, and in what ratios.

I would imagine it is not always possible to trace it to a particular processing facility; however, it is possible to greatly narrow the search, if you know enough about nuclear physics. It could probably be done with several hand-held devices, as well as the knowledge of an expert in nuclear power plant design.

Just my two cents as a former nuclear engineer. Don’t remember all the details anymore.

The exact isotopic ratio of fissile material depends on the feedstock and the processing regime. Each production batch is different. BUT… you can only know this if you have a sample at the end of the production run. So you can only compare the unknown to the stuff you have already sampled. So in The Sum Of All Fears, the unknown bomb sample matches a known sample from Oak Ridge, and the provenance of the plutonium is identified. If the sample had not been matched, then it could be from any other source not being tracked (russian, iranian, indian, pakistani, south african, israeli…).

The IAEA may collect this information from member nations, but probably not.

As for sampling fallout, a reasonable proportion of the plutonium in a nuclear bomb does not actually undergo fission - it gets vapourised and blown to fragments. These fragments can be identified in the fallout and checked - a mass spec is probably the ultimate tool, but a suitably sensitive scintillation device could easily measure the radioactive output of a sample and give a pretty good id on the spot - each component isotope emits radiation of a particular energy, and the scintillation counter can measure those events, giving a suitable analysis.


Some of this sort of information is gathered by the IAEA. Assays are mainly conducted to determine enrichment level. (weapons vs fuel grade) Full gamma ray spectra are collected as a matter of course. They do not disclose these data to any UN member nations, and within the agency this data is kept on a need-to-know basis. Occasionally an outside expert will be required to comment on the data, and in these cases, the source of the data is not identified. If/When a treaty violation is discovered, the evidence may be presented to the UN at large. I’m pretty sure the IAEA is a very “leaky” organization, but they really do try.

In the late 80’s early 90’s I designed several assay devices, and surviellence systems used by the IAEA. I also worked at IAEA headquarters in Vienna for several months.

Except that you only start with a few kilograms of plutonium, and whatever fraction of that doesn’t fiss is going to be scattered over a huge area. Most of the fallout is going to be secondary material, and is going to depend more on what the bomb hit than on what the bomb itself was made of. You might, conceivably, be able to gather enough of it to separate out the traces of plutonium in a fully-stocked lab, and from there be able to get the isotope proportions, but I can’t see how you’d beat the terrible signal-to-noise ratio with an on-site analysis.

Radioactive material condenses from the fireball into Hot Particles. These can be identified by geiger counter. Then an isotopic analysis can be carried out, using gamma ray spectrometry and/or mass spectroscopy. The gamma output of a radionucleotide is specific enough that you can filter out the output from irradiated secondary material from primary fission products and original fissile material. Maybe not handheld, but certainly portable.


As far as Sum of All Fears goes, I read the book but didn’t see the movie because I heard it A)Bore no resemblance to the book, and B)Really sucked in general.

Anyway, they were able to quickly determine the Plutonium’s lineage because, in the novel, the bomb was supposed to have been a sophisticated, 3-stage, fission-fusion-fission thermonuclear device, but the 2nd (and therefore 3rd) stage failed to work, i.e. the bomb fizzled.

Consequently the detonation site was not very big, and more importantly it was very ‘dirty’. Because so much of the nuclear material didn’t chain-react there was a lot of it left and dispersed all over the site.

It has been a while since I read the book, but I thought it was a two stage device - fission-fusion device. The fusion failed because of tritium poisoning (they killed the designer before he mentioned the last minute filtering stage), but the initial fission stage went off just fine. It was low yield (just enough to trigger fusion), but the original bomb would not have had much more than a critical mass of Pu to start with. Not enough for a true third stage, anyhow. Critical mass is critical mass, bomb geometry just modifies how you get it together fast enough to stop it all blowing apart too early.

Unlike the North Korean bomb, which was a true first stage fizzle, and probably plastered Pu all over the walls of the cavern they set it off in, with relatively little vaporisation.


Your memory is spot on, the tritium had been in storage for a while and much of it had decayed to helium.