High-tech experiment merely first, uncertain step to find Fukushima Daiichi's melted cores

As reported by the Asahi Shimbun, cosmic rays called muons will be studied in an attempt to see the "shadow" of what highly radioactive nuclear fuel may still remain in the melted down reactor cores at Fukushima Daiichi, starting with Unit 1.

Estimates vary from the optimistic -- perhaps half of the core remains in the reactor pressure vessel (RPV) -- to the likely more realistic -- "almost all" of the core melted through the bottom of the RPV, fell to the concrete floor beneath, and likely melted some distance down into the concrete and steel layers of the radiological containment structures, if not entirely through them. The exact status of the melted cores remains largely to entirely unknown, nearly four years after the nuclear catastrophe began.

The high-tech experiment is highly uncertain, and limited in its resolution, as well as what areas of the wrecked reactors can be examined.