You'd see other isotopes if it was something recent. It's hard to hide things like this, see the Ruthenium plume that was detected over Europe in 2017 [0]. Radi

You'd see other isotopes if it was something recent. It's hard to hide things like this, see the Ruthenium plume that was detected over Europe in 2017 [0]. Radiation instruments are very sensitive! [0] https://cen.acs.org/safety/industrial-safety/caused-plume-radioactive-ruthenium-Europe/97/web/2019/07 https://cen.acs.org/safety/industrial-safety/caused-plume-ra...