Safety assistance system warns of dirty bombs

Safety assistance system warns of dirty bombs

The threat of terrorism in Europe has been on the rise in recent years, with experts, politicians and security agencies particularly worried that terrorists might make use of “dirty bombs”, where radioactive material is mixed into conventional explosives so that it is scattered by a subsequent explosion.

Researchers in Germany have developed a new system that will be able to detect possible carriers of radioactive substances, even in large crowds of people.

Dirty bombs are not a form of nuclear weapon, since they do not rely on a nuclear chain reaction occurring after they have been set off. The radioisotopes needed to make dirty bombs, such as cesium-137, are easy to acquire; they are used in many nuclear medicine departments at hospitals and in research centres, for example.

“Five grams of cesium – scattered by a couple of kilograms of explosive – is enough to cause billions of dollars’ worth of damage, to say nothing of the psychosocial effects and the impact on health,” says Prof. Wolfgang Koch, a mathematician and physicist who heads the sensor data and information fusion department at the Fraunhofer Institute for Communication, Information Processing and Ergonomics (FKIE).

Fraunhofer FKIE has developed an assistance system capable of detecting radiological threats in a stream of people and warning security personnel. It comprises several components…

The sensor network is made up of gamma spectrometers. “Most of the materials that lend themselves to being used in a radiological bomb emit gamma radiation, which cannot be shielded. That’s why we use this kind of sensor,” Koch explains.

The next phase of the system will be able to tell which substance is emitting the radiation, and whether it is being carried on someone’s person or is present inside their body – perhaps because they are on medication such as radioactive iodine.

Although individual sensors can provide data on the type of material and the intensity of its radiation, they cannot pinpoint its location. This calls for Kinect cameras, as used in the gaming industry.

The advantage of these cameras is that they provide images and information about distance. Mounted on the ceiling, they record groups of people like a hilly landscape, precisely tracking even the busiest streams of people. “We know at any given point where each person is located, but of course, we don’t know their identity – and that is an essential consideration for data protection,” Koch adds.

Once these devices are connected to each other, they can record people in both time and space. Sophisticated mathematical evaluation algorithms then filter out the desired information from the huge amounts of data.

“We use artificial intelligence to do this. The algorithms help us calculate the movements of the only person with whom the gamma sensor readings can be correlated. That identifies the potential attacker,” Koch explains.

Fraunhofer FKIE has been granted permission to experiment with weak radioactive substances, and has already successfully tested its system in the laboratory under the supervision of a radiation control agent.

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