welcome! There's some aspects about the differential between nuclear ogives and dirty bombs. Since nuclear ogives, are manafactured so to implode on a very high speed, and with dozens of tons of weight of impact on the target. The dirty bomb, can only have 10% of this effect if, added 3 types of explosive, including gas (specially ethylene oxide) ; Of course, 10 grms of HEU are for 7 nuclear ogives, as 10 grms of HEU (osmium, rhodium, barium, americium...etc) are for a dirty bomb, since 10 grms are equivalent to 100.000 microcuries (radiation of neutrons) ; Trought the years, of my research, there's trillions of internet sites, and I found 1 ! able to explain me, that a dirty bomb with 10 grms HEU, would kill a very small nervouse center of people in Manhatan , but would definetly create a trillion dollars loss, because it would disable the all energy grid, for months! Also, from research, the russians seized a dirty bomb back in 2011, on a park at Moscow, and arrested 3 chechians, this bomb actually, would be just a pratical joke, as I told you before, it need 3 types of iniciators.