With speculation that the Zelensky regime is planning to follow up on its invasion of Kursk with nuclear “dirty bomb” attacks there and/or at Zaporozhiye, there is an interesting (albeit long) comment on the physics of the potential nuclear contamination at Simplicius’s blog. Worth reading. With a hat tip to commentator “John Galtsky”, his observations are repeated below:
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A few comments, starting with a technical answer to a technical question:
“But logically speaking, why would you need nuclear material of your own, if you already plan to hit the storage casks which contain spent fuel rods, if you want to create a nuclear contamination incident?”
Short answer: either as a military weapon to create killing radiation using isotopes not normally found in spent nuclear fuel, or as an area-denial weapon to contaminate an inconveniently large area with relatively non-lethal but still dangerous isotopes in a way that cannot be accomplished by targeting spent fuel casks. In both cases, setting off such a weapon over the fuel storage area will sow confusion and generate fear propaganda because of widespread ignorance and fear of spent nuclear fuel.
Onward to a fuller explanation…
Spent nuclear fuel storage casks are exceptionally strong, very thick steel and concrete containers that each contain a relatively limited amount of spent fuel so that heat doesn’t build up. Even a very massive warhead, as in the largest of Kiev’s available cruise missiles, might not break through them but just scatter them in mostly intact form. Artillery rounds and smaller warheads as found on Kiev’s longer range or smaller drones are unlikely to do any significant damage to the casks.
Contrary to popular myth, the spent fuel rods inside those storage casks are not all that dangerous in any event. They’ve been cooling with their active elements decaying for years now, so the really active, and thus highly radioactive elements in them have already decayed, leaving those elements that have longer half lives, which means they decay much slower and thus emit much less radioactivity. You still wouldn’t want to be handling it or standing around it taking selfies while embracing the spent fuel rods, but it’s not remotely as dangerous as people think in panic, believing it will kill you in minutes through a crack in the cask at 100 paces.
The paradoxical thing about radioactive hazards is that radioactivity comes from decaying nuclei. The more nuclei decay per second, the more radioactivity you get. But each nucleus decays only once. Radioactive elements which emit the most radioactivity do so because they have lots of nuclei that are decaying very rapidly with short half lives. But because they have lots of nuclei decaying rapidly, the number of nuclei that are available to decay drops very rapidly.
So what’s a dangerous dose?
A dose of about 500 rems all at once is enough that over a period of days or a week or two you’ll die. The first day it is pulled from a reactor a spent fuel assembly emits about 10,000 rems per hour. That sounds ferocious, but it works out to only 166 rems per minute. You could stand safely far away, run up to the fuel rod and snap a quick selfie, and then run back, the whole process taking 20 seconds and you’d only get 56 rems. That’s not enough that most people would feel any effects beyond possibly feeling like they were hungover for a few days. Hug the fuel assembly for three minutes and yes, you’d die within a couple of weeks, but no, even fresh out of the reactor it won’t kill you in seconds at a hundred paces.
The radioactivity of the spent fuel assembly declines fairly rapidly after that. In a few years it would be emitting less than 1000 rems per hour. In 40 years it would emit about 10 rems per hour, giving you a lower dose in an hour than the cosmic ray radiation flight crews absorb in airplanes in a year or two of flying between the US and Europe.
The type of radiation also matters. Most fission products in spent fuel emit beta radiation, which is extremely weak: a sheet of thick cardboard will stop it. They’re not dangerous unless you inhale them or ingest them, because then their atoms can be close enough to sensitive cells in your body to kill them within the very short range their radiation can travel.
More dangerous are fission products that emit penetrating gamma radiation. The classic example is cobalt 60, an artificial isotope of cobalt that emits very high power gamma radiation. It has a half life of 4.3 years, which means half of it is gone ever 4.3 years. But spent fuel rods do not contain significant amounts of cobalt 60 because there’s no starting, inert cobalt in those rods to begin with. You have to deliberately create cobalt 60 in a reactor by substituting some of the fuel rods with rods that are inert cobalt 59, which the reactor over time will transform into cobalt 60.
The fission products in spent fuel that people panic about are things like iodine 129 which is a weak beta emitter with a half life of 15.7 million years, and technetium 99, also a weak beta emitter with a half life of 211,000 years. As weak as they are, people panic about them getting into the food chain and thus being ingested by humans. They may be very weak radioactive elements, but because they are long lived people panic about even small amounts of them being in the environment. But when you compare their possible very long term lethality (through causing cancer or whatever), they’re not remotely as dangerous as heavy metals like cadmium or lead, which hang around forever and don’t decay, and which are pumped into the environment through leaded fuels and such to the tune of millions of tons.
Kiev’s best plan for a dirty bomb is to have replaced some of the fuel rods in the reactors Kiev controls with cobalt rods over the past ten years, and perhaps also cesium breeding rods, to build up a stock of highly radioactive cobalt 60 plus lots of highly radioactive cesium 137 (30 years half life, also a strong gamma emitter). Wrap the cobalt 60 and cesium 137 around explosives and you have a “dirty” bomb that will make it very dangerous for people to enter the region where it was exploded because the gamma radiation would be enough to sicken or even kill soldiers spending tens of minutes or hours in the immediate area of the explosion, likely a region that is the size of a couple of football fields depending on how much cobalt 60 they have.
That could deny access to the Zaporozhiye nuclear plant, and it could seriously enrage Russia as a bona fide “nuclear” attack, pushing Russia into a strong enough escalatory response to cause direct war between Russia and the US/NATO.
A second possibility is to take spent fuel rods from Kiev’s nuclear plants and to extract the 4% of material which are fission products, concentrating the spent fuel down to the 4% that is strongly radioactive. Those will be mostly beta emitters with radiation that the thickness of your skin would stop, but they would be very active initially and then some of them would hang around for a long time leading to a long term decontamination task for the area they contaminated. Kiev could then wrap a few hundred kilograms of that around explosives and set that off over the Zaporozhiye plant, hoping to generate a Chernobyl-style exclusion zone and to foment panic in civilian populations.
Other than the “enraging Russia” bit, from a military perspective that would be a very local denial of access because of the limited ability of Kiev to deliver enough extracted fission products and to vaporize them effectively for wide dispersion by wind. Chernobyl involved many tons of fission products that were vaporized and dispersed by huge amounts of energy from a reactor core burning with the assisted power of an active, massive, out of control, nuclear chain reaction. A dirty bomb can deliver far smaller amounts of fission products, and those would be pulverized and dispersed by a chemical explosive with a tiny fraction of the power of the Chernobyl event.
Given that virtually nobody in the West knows anything about such matters and the very few who do lie about them as shills for the US, all we will hear is that Russia blew up its own fuel storage facility and the result is widespread contamination reaching into Ukraine and Europe. All the technical evidence demonstrating that’s a lie will go unreported or ignored.
