The 2E5 Bq shown for U-235 implies about 2.5g (at 8E4 Bq/g). In the field, if the detector is held right on the sample (which can be done with the Inspector 1000), we usually multiply by 3 to account for the solid angle. This gives about 7.5g of U-235 — which implies 0.75% U-235 if the total sample is 1 kg, as stated in the report. 0.75% is synonymous with natural uranium, no enrichment.

I can’t explain the very high activity seen for U-238. It’s hard to “mask” or spoof spectroscopic detectors – if you tried to sneak in Co-60, Ba-133, or another commonly available radiation source, the spectroscopic detector would identify it as such. The only “masking” isotope would be Th-230, which is a daughter product in the decay chain of U-238 and gives off some characteristic gamma rays that are energetic enough to measure. If you somehow got a quantity of Th-230 (which is hard because it’s not commercially available), you could just maybe fool the detector into thinking there is a lot of U-238 there. But that’s a long shot. The simpler explanation is “operator error.”

The “terror” effect would be comparable, while being easier to obtain.

For a while in Baghdad insurgents placed gas tanks near IEDs. the gas itself was harmless or just slightly irritating but the psychological effect of the IED augmented manifold.

Thanks for posting, it’s always interesting to read informed thoughts.

Marcello

REPLY: This is an interesting point that I confess I had not thought of: What difference does it make how dangerous uranium really is? Dirty bombs are often called weapons of mass disruption rather than weapons of mass destruction because the damage they do might be more from social and psychological factors than actual physical damage. So if everyone thinks that uranium is dangerous, it might have much the same of effect as if uranium actually were dangerous. Certainly an interesting idea to consider.