Within ten years, Tokyo Electric Power Co. hopes to begin removing the damaged fuel from three reactors at its tsunami-hammered Fukushima Daiichi nuclear plant. Determining exactly where melted fuel came to rest is among the daunting problems faced by TEPCO’s engineers, and Japanese scientists are studying a new technology to look inside the reactors.
The Japanese government has offered funding to a team at Nagoya University to refine a system that can observe the path of muons through solid objects. Muons are subatomic particles created when cosmic rays hit the earth’s upper atmosphere. They fall to earth continuously and have the ability to travel through dense matter like rock or concrete that traditional imaging, such as X-ray technologies, cannot penetrate. The greater the density of a material, the more muons it can absorb. Uranium is more dense than steel, so researchers hope to map out the fuel by charting the muons that make it through the reactor.
The concept has been validated by a scientist at the University of Tokyo who used a device that detects muons to make a 3D model of Mount Asama, 90 miles from Tokyo. Creating and tracking images of the previously inaccessible “throat” of the active volcano gives scientists a better understanding of when it might erupt.
The team at Nagoya University’s Kobayashi-Maskawa Institute for the Origin of Particles and the Universe faces the challenge of applying the technology under the conditions at Fukushima. Gamma rays may interfere with the film that detects muons, and researchers may use lead shielding to allow only muons through. The team plans to conduct research specific to the plant when radiation levels subside further, according to the Daily Yomiuri.