Improving remote detection of radioactivity

Technique using pulsed electromagnetic waves might one day sense radioactive material 100 km away

By Jyllian Kemsley

http://cen.acs.org/articles/95/i20/Improving-remote-detection-radioactivity.html

After a nuclear power plant accident, for safety reasons it can be difficult for humans or even robots to get close enough to the facility to assess the situation. To get accurate information without putting people or equipment at risk, responders would benefit from better technology to sense radioactive material from afar. That could come from high-power pulsed electromagnetic waves, reports a team from Ulsan National Institute of Science & Technology (UNIST).

First proposed in 2010 by the University of Maryland’s Gregory S. Nusinovich and colleagues, the approach involves using an antenna to direct high-intensity millimeter or terahertz waves at a target area. If material there is radioactive, γ radiation or α particles ionize the surrounding air, releasing free electrons. The interaction of the antenna-directed electromagnetic waves and ionized air induces plasma formation, and the plasma in turn reflects the electromagnetic waves back to the source site for detection.

The UNIST team, led by EunMi Choi, experimentally demonstrated detection of 0.5 µg of cobalt-60 from 120 cm away, the maximum distance allowed by the laboratory setup (Nat. Commun. 2017, DOI: 10.1038/ncomms15394). Off-the-shelf gyrotrons to generate the electromagnetic waves, antennae to direct them, and radio­frequency detectors could be used to deploy the technique for field detection.

Depending on the equipment used, Choi believes the approach could scale to detect radioactivity at distances of at least tens of kilometers and possibly as far as 100 km. Because the time delay of plasma formation depends on γ emission energy, Choi also thinks the technique could be used to identify types of radioactive material.