EPA uses RadNet monitors to track fluctuations in gamma radiation emitted from airborne radioactive particles at each air monitoring site. Tracking these changes over time gives a picture of the background (normal) levels and allows EPA scientists to detect any unusual changes. These data come to the laboratory as a "gamma count rate," which shows how many gamma rays the monitor detects each minute.
Each hour’s worth of data are split into regions to allow EPA scientists greater sensitivity when identifying anomalous readings. When multiple hours of data are looked at together we can track "normal" or "background" radiation levels at each air monitoring location (see Picture 1). Adding the regions together provides an even simpler way of tracking trends at each monitoring location (see Picture 2).
When the RadNet computer system detects an elevated reading from an air monitor in any of the regions, those data are reviewed by EPA scientists who are specially trained in understanding the data and identifying specific radionuclide(s).
|Picture 1 - Multiple hours of data by energy range||Picture 2 – Single line created when energy ranges are added together|