At the least, it means these particular compounds aren't quickly breaking down into ever-smaller nano-particles that can be absorbed into living things.
But the phrase is actually neutral, it's not making any claims if stability is a good or bad thing in this context, neither about "unexpected" stability. But given the larger context of language we read it as positive.
Of course radioactivity needs to be respected, and the exclusion zone is there for a reason due to factors such as hot spots.
¹ humans contain, on average, 90µg of uranium. [https://www.iaea.org/sites/default/files/DU_Eng.pdf]
(P.S.: the radiological stability and lifetime of uranium doesn't make much sense to question; the dust flakes aren't large & concentrated enough to significantly shorten their half-life due to their own neutron emissions cascading and this isn't what the study was researching. Note the article talks about weathering: "It remains largely unclear why these particles weather at different rates in their environment.")
https://en.wikipedia.org/wiki/Project_PACER
> A series of 50-kiloton bombs would be dropped into the cavern and exploded to heat the water and create steam. The steam would then power a secondary cooling loop for power extraction using a steam turbine. Dropping about two bombs a day would cause the system to reach thermal equilibrium, allowing the continual extraction of about 2 GW of electrical power
Which was building canals etc with nuclear bombs. https://en.wikipedia.org/wiki/Project_Plowshare
It’s strange that controlled fusion is an energy sink, but whatever black magic is happening inside an H-bomb manages to unlock so much “free” energy.
The history of fusion research for the past 70 years is trying to figure out a cost-effective way to trigger enough fusion to make net energy without a nuke. So far, we've got bupkis. (The magnetic containment approaches using high-temperature superconductors seem promising, but we won't know they actually work until we've built them.)
Thermonuclear bombs literally create lots of heat, and don’t tend to drive anything that produces work. It’s the opposite of efficient.
Just like lighting gasoline on fire and claiming that that’s more efficient than a combustion energy…
Further fission here requires a fission first stage which represents a huge additional energy input.
I trust the argument. You can look into it yourself. Long story short, it is massively energy positive compared to controlled fusion.
So, fission bombs are the black magic.
It’s a much more efficient version of inertial confinement fusion like at the NIF.