When you have 2000 nukes you don’t need dirty bombs for area denial the only ones who would be interested in dirty bombs would be non-state actors and those can’t build one and the few non-state actors that could are most part not stupid enough to build one because they actually want to keep what ever little regional power they have.
Also reactor fuel is a terrible material for a dirty bomb because of its long half life time, you need materials which are much more active than that to be effective like those used in radioactive medicine and sensors those isotopes and are much more controlled than processed nuclear fuel and for a good reason.
