First results of radioxenon detection system in Lithuania capable to trace radioxenon release from different sources

Radioxenon measurement network consisting of four automated stations was deployed at the end of 2024 in Lithuania to trace radioxenon (Xe) releases from the different sources: nuclear power plants (NPPs) in neighboring countries, medical isotope production facilities (IPFs) and military or peaceful nuclear explosions (NEs). The Belarusian NPP, which operates two VVER-1200 reactors, is the closest nuclear facility. It is located just 20 kilometres from the Lithuanian border and 50 kilometres from Vilnius, the capital city. This makes it the most likely source of xenon (Xe) detections. Data of one-year Xe isotopes monitoring in Lithuanian (LT) national network revealed few episodes with several Xe isotopes detections. Episodes were analysed to identify likely release sources by evaluating the possible source region (PSR). This assessment was conducted using atmospheric transport modelling (ATM), incorporating archived HYSPLIT meteorological data for backward trajectory calculations and the JRODOS code for forward simulations. The Lithuanian network demonstrates capability to detect Xe isotopes for effective emergency response and risk mitigation purposes at national level, but also could support the Comprehensive Nuclear-Test- Ban Treaty (CTBT) with the Xe data for better source localization if needed.