DARPA tested an awesome plan to find dirty bombs

The Defense Advanced Research Projects Agency held a massive scavenger hunt in the nation's capitol to collect data on how to find dirty nuclear bombs planted by terrorists.

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Participants in the scavenger hunt, mostly ROTC cadets and midshipmen from the nearby Naval Academy, were playing a game to find a geneticist who was "mysteriously abducted." But they carried cell-phone sized sensors that sniffed out radioactive material as they moved around the city for hours, allowing DARPA to test the ability of the sensors to search for a covert nuke.

The sensors, part of DARPA's SIGMA program, are low-cost gamma and neutron radiation sniffers that are networked with smartphones so they can relay information to a central point.

Before this scavenger hunt, DARPA had only tested up to 100 sensors at a time. But the network of sensors is supposed to provide coverage of entire cities or regions, allowing law enforcement to search for and find stolen or smuggled nuclear material before it can be used in a weapon.

In a real attack, police would need to scan vast areas using hundreds or more sensors. So, the Nov. 10 test featured 1,000 sensors feeding their information into the program's software.

The scavenger hunt scenario was developed to keep the cadets and midshipmen engaged as they carried the devices around Washington, D.C., for hours. Even larger tests are planned for 2017 and DARPA partners hope to push the final version of SIGMA to local, state, and federal police in 2018.

Dirty bombs are conventional explosives with nuclear material mixed in or layered on top of the main charge. The nuclear material does not significantly add to the total blast force of the weapon, but it is spread over a large area to frighten residents and to force a costly and time-consuming cleanup process.

Dirty bombs are easier to make than standard nuclear devices, and the government has worked to prevent a dirty bomb terrorist attack for years.