A 1000 Curie Cs137 dirty bomb driven by 100 kg of TNT on a day with 5 km/hr winds out of the East, popped off 5m above the ground will make a plume that will dose people to 100R Total Effective Dose Equivalent over a .027 square kilometer area (six acres) and a TEDE of 10 millirems over a 0.19 square km area. If I run the dose contour down to 0.1 millirem, then I get the huge area of about 250 square km- but the dose is very very low. The area with a dangerous dose is 6.6 acres, not small by any means but not “a hundred square miles”. A ten millirem dose is undesirable in the general population but is hundreds of times less than a CAT scan (for comparison).
When they say “substantial amount” they must mean the entire contents of a hundred or so hospital-strength irradiators to get up to the “hundred square mile” area. That would be bad! I suspect, though, that once the bad guys stole the first kilocurie, everyone would be on high alert everywhere.
Here’s a geek dump from the simulator:
Source Material : Cs-137
Source Term : 1000 Ci
Airborne Fraction : 1.000
Respirable Fraction : 0.500
Respirable Release Fraction: 0.500
Wind Speed (h=10 m) : 5.0 m/s
Distance Coordinates : All distances are on the Plume Centerline
High Explosive : 100.00 Pounds of TNT
Debris Cloud Top : 240 m
TEDE includes : Inhalation dose + Submersion
Maximum Dose Distance : 0.010 km
MAXIMUM TEDE : 0.043 rem
Inner Contour Dose : 1.0 rem
Middle Contour Dose : 0.500 rem
Outer Contour Dose : 0.100 rem
Exceeds Inner Dose Out To : Not Exceeded
Exceeds Middle Dose Out To : Not Exceeded
Exceeds Outer Dose Out To : Not Exceeded
This sort of attack would be very frightening and a nightmare to clean up. The public would demand that every single bit blown anywhere must be cleaned up (rightfully so) and the whole thing would cost a huge amount and would change the way people think forever. Cleaning up the six acres close to the center would actually be easier than cleaning the 250 sq km at the lower dose.
But as for an actual hazards due to the radiation, they are not that bad in the short term and limited to close up to the actual blast. Breathing in Cs137 is not healthy, but as Europe can attest, not immediately fatal. Chernobyl dumped a gargantuan amount in the air and millions of people breathed it in.
A tiny amount of a radioactive material can make a Geiger click, even amounts that are not harmful like gas lantern mantles, Vaseline glass, and old Fiestaware plates. Any one of these common items will send a counter into hysterical fits, as would a tiny speck of Cs137, which would need to be cleaned up.
Severe decimal error. I reran the sim and got 0.1 REM for the 6 acre area, even adding in an extended stay. It’s not 100 R.
Still a bear of a cleanup, though!