I'm not sure it's that simple. The bombs probably don't "barely work" at 10% of explosive power. It's more likely that 90% of them do not work at all, and 10% of them do. Numbers made up without basis.
Russia starts to look very awkward if they launch a nuclear attack and it does not work. What happens next? The loss of credibility drops substantially with each attack. I think, for this reason, a nuclear attack on ukraine is not likely to happen.
This is a better view. It’s not just about what happens if it works but also about what of it does not. In both the scenarios though, Russia itself be facing an existential crisis since nuclear powers are dime a dozen at this point in the world and they will fight back.
Edit: As spywaregorillla corrected me, there are only a few countries with nuclear weapons. 8 in number other than Russia.
Wont a conventional explosive wrapped around a nuclear payload (ie a dirty bomb) do a whole lot of damage from the radiation? The blasts don't concern me, cities can be rebuilt, but not if the land is radioactive for a hundred years.
Chernobyl was effectively a "dirty bomb." It was bad, but not nearly as bad as was predicted. Many people have visited the Chernobyl exclusion zone (legally and illegally) and found it is doing pretty well. (Most recent visitors were Russian soldiers - Russia actually invaded Ukraine through the Chernobyl exclusion zone.)
Not an expert but I think no, that's not how that works. You can't detonate a nuclear weapon without the mechanism to enact the fission. A dirty bomb meaning just a normal explosion with some radioactivity in it, is probably... not actually that bad? At least, not in the context of how bad things are already. Hundred years sounds far too long.
Russia starts to look very awkward if they launch a nuclear attack and it does not work. What happens next? The loss of credibility drops substantially with each attack. I think, for this reason, a nuclear attack on ukraine is not likely to happen.