When the xenon-isotope ratio was tested for Chernobyl, that was one explosion from one reactor. But Fukushima has seen multiple events from multiple reactors, as well as sustained emissions.

Unless a sample was taken from the plume in the air shortly after the Unit-3 blast, is a sufficiently clean sample of xenon emissions from Unit 3 possible? Unit 4 exploded after U3, so even ejecta next to U3 could be mixed. Could testing reliably sort that out?