re: "Russia Denies Causing Latest Radioactivity Over Europe; UN Agency Says Origin "Still Unclear"
https://www.technosotnya.com/2020/06/avariya-na-aes-v-rf-dorogi-perekryty-v-peterburg-dvizhetsya-voennaya-kolonna-video.html?m=1
Article in Russian, but seems to indicate reactor trouble near St Petersburg