Waveform data help identify the location of an event and qualify it as either natural or potentially man-made. However, they cannot reliably answer the question as to whether a man-made event, such as an explosion, was nuclear or not. The only reliable way to answer this question is to trace and analyse the radioactive remains of a potential nuclear explosion.  Some of these remains provide the ultimate proof for the nuclear nature of an event and are therefore referred to as the ‘smoking gun’.Radionuclide monitoring data from the 80 radionuclide monitoring stations worldwide are expected to shed light on this key question. Data on radionuclide observations are sent to the International Data Centre (IDC), where they undergo an analysis process like waveform data. After the automatic analysis process, analysts refine the results during interactive review.

Each radionuclide particulate monitoring station sends one gamma ray spectrum per day. A gamma ray spectrum is a two-dimensional plot showing which radionuclides were observed in a single sample and in what quantity.

During radioactive decay, most radionuclides emit a very specific quantity of energy, which can take the form of alpha, beta or gamma radiation. As the energy of gamma radiation is known for each isotope’s radioactive decay process, the measuring of gamma radiation allows the conclusive identification of an isotope in the spectrum.