Yeah i thought the HEU was the good stuff, not for dirty bombs. 37 lbs?! How much was in the Hiroshima bomb?
Apparently not enough, hence the need for Nagasaki.
About 140 pounds, but that was back when the equipment and methods were pretty crude. Today 37 pounds is enough.
Here's the real question. Where was it made and how much more has already been produced and delivered from that facility?
"The IAEA defines a "significant quantity" (SQ) of HEU, the amount needed to make a nuclear bomb, as 25 kilograms." Source
25 kg = 55.115 pounds. Almost.
That bomb had 110 pounds on enriched Uranium in a concave/bullet spherical configuration necessary to facilitate a chain reaction. The bomb had a 12.5 kiloton explosive yield.
The Nagasaki bomb held 35 pounds of Plutonium with a 32-part implosion detonator coupled with a Beryllium/Polonium injector in order to facilitate the chain reaction. That bomb also had a 12.5 kilton explosive yield.
Thermonuclear (fusion) bombs are another story altogether...