Talk about clever idea. The people dealing with the Fukushima Daiichi reactors do not have any idea what the core looks like or where it is - it melted down and is to hot to observe either in person or with instrumentation. Anything that gets close to it will be burned out.
From World Nuclear News:
Cosmic rays to pinpoint Fukushima cores
Middleburg, Virginia-based DSIC will design, manufacture and deliver two muon detectors that will fit into the power plant building. The detectors will be part of Toshiba's overall Fukushima Complex project to determine the location and condition of the nuclear fuel inside the plant. The value of the contract has not been disclosed.
Muons are high-energy subatomic particles that are created when cosmic rays enter Earth's upper atmosphere. These particles naturally and harmlessly strike the Earth's surface at a rate of some 10,000 muons per square meter. Muon tracking devices detect and track these particles as they pass through objects. Subtle changes in the trajectory of the muons as they penetrate materials and change in direction correlate with material density. Nuclear materials such as uranium and plutonium are very dense and are therefore relatively easy to identify. DSIC has already applied the technology in its Multi-Mode Passive Detection System, used at ports for scanning containers for radioactive materials.
The 3-D image produced by the detectors should give a clear picture of the condition and location of the fuel in the cores of the three damaged reactor at Fukushima Daiichi. This will assist Toshiba in developing a safe and effective remediation plan.
Very clever - they are doing tomography on the cores using cosmic muons.
DSIC's website is here: Decision Sciences International Corporation - they do a lot of nuclear security - scanning shipping containers, etc...