Cosmic rays could probe Fukushima reactors

U.S. researchers say cosmic rays could be used to gather detailed information from inside the damaged cores of the Fukushima Daiichi nuclear reactors in Japan. Scientists from the Los Alamos National Laboratory said a process called muon radiography could provide a look inside the reactors that were heavily damaged in March 2011 by a tsunami that followed a huge earthquake. Muon radiography, also called cosmic-ray radiography, uses secondary particles generated when cosmic rays collide with upper regions of Earth's atmosphere to create images of the objects that the particles, called muons, penetrate, a Los Alamos lab release said Wednesday. With massive numbers of muons showering the planet every second, Los Alamos researchers found detailed images could be gathered by placing a pair of muon detectors in front of and behind an object, and then measuring the degree of scatter the muons underwent as they interacted with the materials they penetrated. The process is similar to the way X-ray images are produced, except muons are produced naturally and do not damage the materials they penetrate, they said. The process could provide high-resolution image data of potentially damaged nuclear material inside the reactors, scientists said. "We now have a concept by which the Japanese can gather crucial data about what is going on inside their damaged reactor cores with minimal human exposure to the high radiation fields that exist in proximity to the reactor buildings," Konstantin Borozdin of Los Alamos' Subatomic Physics Group said. "Muon images could be valuable in more effectively planning and executing faster remediation of the reactor complex. "As people may recall from previous nuclear reactor accidents, being able to effectively locate damaged portions of a reactor core is a key to effective, efficient cleanup," he said.