TOKYO, Jan. 23 (Kyodo) — A team of Japanese researchers said Thursday it has developed a cosmic ray-based system to produce visual images of nuclear fuel that has melted down at Tokyo Electric Power Co.'s Fukushima Daiichi nuclear plant.
The team successfully used cosmic rays to produce images of nuclear fuel from outside an off-line nuclear plant in Tokai, Ibaraki Prefecture, in an experiment between February 2012 and December 2013.
Nuclear fuel melted down at three reactors of the TEPCO nuclear plant when the devastating earthquake and tsunami hit northeastern Japan in March 2011. The condition of the melted nuclear fuel remains unknown in the inaccessible reactors.
"The (cosmic ray) measurement system can be installed easily," said team member Hidekazu Kakuno, associate professor at Tokyo Metropolitan University. "We are ready to use it at the Fukushima Daiichi plant if TEPCO cooperates."
The team, which also includes researchers from the High Energy Accelerator Research Organization, tracks the so-called muon particle, which is produced by cosmic rays' reaction with the atmosphere and changes its course when coming into contact with nuclear fuel.
In the experiment, it installed three muon measurement systems outside the Tokai nuclear plant and analyzed measurement data to visualize nuclear fuel located in a pool neighboring a reactor and the framework of a reactor building.