The JRC operates a laboratory for ultra low-level radioactivity measurements inside the 225m deep underground laboratory HADES, which is operated by EURIDICE and located at the premises of the Belgian Nuclear Research Centre. 

In HADES, the muon flux (secondary cosmic rays) is a factor of 5000 lower compared to above ground and the flux of protons, neutrons and electrons is reduced to an insignificant level. This reduction of the cosmic ray flux makes the background in gamma-ray spectrometry measurements significantly lower compared to above ground. Therefore it is possible to detect very low amounts of radioactivity, for example levels of some hundred μBq (micro-Becquerel, i.e. a few nuclear disintegrations per day).