Kyiv could rapidly develop a rudimentary weapon similar to that dropped on Nagasaki in 1945 to stop Russia if the US cuts military aid, it has been suggested
That's actually not too crazy of an idea. A large part of land is mined and basically unusable for a long while and modern nukes are way less and way shorter radioactive. Blasting away a large part of Russian soldiers at once would send a big message.
Depends on the size of the area you're considering. In some area, one nuke would blow up 100% of the mines. But in some other, larger, area, it would only blow up 50%.
But to be fair, using nukes to clear mines is probably one of the least effective methods considering all the collateral damage on villages, fields and nature.