News sources report that Tokyo Electric Power Company (TEPCO) has concluded --as already widely speculated-- that the entire reactor core for Fukushima Daiichi Unit 1 completely melted down following Japan's March 11, 2011 nuclear catastrophe. TEPCO is using “muon” detectors for the imaging of cosmic rays coming from outer space as they pass matter like the concrete and steel of Fukushima and absorbed in high-density molecular materials like uranium in an effort to locate the destroyed radioactive reactor cores. Muon imaging for Units 2 and 3 is still underway.
SimplyInfo reports that the x-ray like imagery indicates that the center portion of the bottom of the reactor pressure vessel appears to be missing and that the melted reactor core material has exited and relocated outside of the reactor vessel.
The exact location of the destroyed reactor cores for Fukushima Daiichi Unit 1, Unit 2 and 3 remain unknown. The muon technique is not useful for melted nuclear fuel at the base of the containment or beyond which cannot be imaged as the cosmic particles are not coming from below the reactors. TEPCO is attempting to probe beneath the wreckage for missing reactor core material with advanced robotics.