The imaging suggests that corium has run down into the basement of the primary containment structure - recall the elephant's foot at CNPP. There's distortion and a 2m wide hole in one side of the pedestal grid structure (where
previous images suggest some fuel may be located) below the pressure vessel - most likely where the corium (likely the source of the high readings) has flowed through it.
TEPCO have produced a
document illustrating the location relative to the RPV.
The most recent muon tomography of reactor 2 was somewhat inconclusive but at the very least suggested fuel had either pooled towards the bottom of the RPV or (more likely) passed through into the containment.