First it was cold shutdown, then it became meltdown, what if most of it had been expelled in the skies, and if so how long it will take for them to finally admit it to the world...
The group includes researchers from Nagoya University. It has been probing the plant's No. 2 reactor since April of last year, using a device that uses elementary particles called muons to see into its interior.
The researchers say the results of their study show few signs of nuclear fuel at the reactor core, in contrast to the No. 5 reactor where fuel was clearly visible at its core.
This led them to believe that 70 to 100 percent of fuel at the reactor has likely melted.
The researchers say further analyses are needed to determine whether molten fuel penetrated the reactor and fell down.
The No.2 reactor is said to have released large amounts of radioactive substances following the March 2011 accident.
Tokyo Electric Power Company, the plant's operator, has estimated that part of nuclear fuel at the reactor remains at its core.
The locations of nuclear fuel will have a significant impact on the process to remove it from the damaged reactors, the most difficult step of the decommissioning work.
The Japanese government and TEPCO plan to scan the No. 2 reactor once again using a different device.
They are also preparing to use robots around the reactor.
The group will announce the results of its study at a meeting of the Physical Society of Japan in Osaka on Saturday.