Nukes make terrible dirty bombs the isotopes in questions are very stable and not highly radioactive, for a dirty bomb you want isotopes with a fairly short lif

Nukes make terrible dirty bombs the isotopes in questions are very stable and not highly radioactive, for a dirty bomb you want isotopes with a fairly short lifetime of years/decades. PU239 has a half life of 24,110 years and that's your best case for a dirty bomb, if the core is U235 then it has a half life of 703,800,000 years which means when it's not in any substantial mass in which the nuclear decay is can to turn into a chain reaction it's about as radioactive as cat litter or a banana.