Source estimation analysis of radioxenon detected at Mongolian radionuclide monitoring station and diffusion analysis from the emission source

Yamamoto, Yoichi ; Furuno, Akiko  ; Kurihara, Toshiyuki ; Tomita, Yutaka 

Radioxenon is a high-yield fission product which is an important tracer for a nuclear test, and is also emitted by civil nuclear facilities like isotope production facilities or nuclear power plants. The Ulaanbaatar radionuclide monitoring station (MNX45) in Mongolia has detected relatively high concentrations of Xe-133 exceeding 1 mBq/m several times a year, despite the fact that there are no nuclear facilities in the vicinity that could be sources of emissions. To determine the source of emission, Atmospheric Transport Modelling (ATM) backtracking analyses for source estimation were carried out for five cases with consecutive detections of Xe-133 above 1 mBq/m since September 2023. For these cases, forward tracking analyses from the estimated sources of emissions were carried out to investigate the impact of detected Xe-133 on radionuclide monitoring stations located downwind from MNX45. We report on the analysis and results.