Suitcase bombs from power plants?

What is the real likehood that terrorists could build a-bombs as a direct result of a dramatic increase in the use of nuclear power in the US?
There is a significant increase in interest (including from me) in taking another look at building more nuclear powerplants, and this question often comes up, and I don’t know if it’s a real possibility.
Assume that our society remains pretty much as it is right now.

An actual Nuclear device? Essentially zero. The fuel used in power generation is nowhere near pure enough for bomb use.

A dirty bomb? Possible, since there is a lot of radioactive waste that gets generated and stored. Still, probably pretty unlikely.

Even for a dirty bomb, most of the waste is mildly radioactive stuff like gloves and protective clothing that has been contaminated while in use in the plant, rather than actual fuel.

It is pretty easy to “poison” even highly enriched uranium with other neutron-absorbing isotopes such that it is completely unsuited to fission weapon usage; indeed, the big difficulty with plutonium production is a continuous process of filtering out the desired [sup]239[/sup]Pu from the more unstable and neutron absorbing [sup]240[/sup]Pu. ([sup]240[/sup]Pu cannot be chemically separated from [sup]239[/sup]Pu, and centrifugal extraction is impractical for usable masses). Other fast neutron absorbing isotopes could also be included in nuclear fuel without significantly hampering its use in power production.

As the radioactive component in a “dirty bomb”, the material would still be useful, of course, but one can say that about any radioactive isotope that is biologically reactive. Although if inhaled in powder from plutonium can be quite deadly in small amounts, it is not especially dangerous in solid form, and especially if contained in fuel elements. Aerosolizing plutonium (or any other solid radioactive isotope) for effective use as a radiobiological weapon is very difficult, owing to the density (i.e. it doesn’t remain suspended very well as a particulate) and the fact that as a metal it resists being ground into a molecular-grained powder form. Like mercury, the biological hazard of it in small amounts over a short exposure period are widely overstated, although long-term exposure in the environment, even at low levels, will inevitably lead to higher incidences of chronic heavy metal toxicity, cancers and immune diseases, et cetera.

A “suitcase bomb”, i.e. a nuclear weapon compact and light enough to be carried in even a large suitcase would be the work of an advanced program with access to modern production facilities and a bounty of technical knowledge and test data. This is well beyond the capability of a small organization, even one that is reasonably well-funded and able to recruit from general technical ranks. A medium-sized nation with substantial technical resources (say, Japan) or a very well funded group of physicists and engineers experienced in nuclear physics and computational explosive hydrodynamics could probably pull this off, but I’d be highly surprised if even an established terrorist organization could muster the resources. And one that was able to could and would probably produce their own material from a self-built breeder reactor (albeit not one designed to produce electrical power; if all you want to do is breed fissile material you can make the pile smaller and the reactor much less complex).

On the whole, this is way down on the list of possible threats. More likely is for terrorists to grab nuclear or biological waste and dump it in the water supply or ground water source to a major metropolitan or agricultural area.


My interest was piqued the other night by seeing part of a PBS program about these modular reactors.