Source Localization of Ruthenium-106 Detections in Autumn 2017 Using Inverse Modelling

In late September and October 2017, Ru-103 and Ru-106 have been detected throughout the northern hemisphere by national environmental radioactivity monitoring networks and by the International Monitoring System that is being established to verify compliance with the Comprehensive Nuclear-Test-Ban Treaty. Ru-103 (half-life: 39.26 d) and Ru-106 (half-life: 373.6 d) are radioactive particulates that have no natural sources and for which there is no measurable global background.