Thorium Threshold energy

If reasonable amounts of negative quarks could be had in a sample, energetic photons just above the threshold can ionize the quark to a free state with moderate kinetic energy. One advantage of such an experiment liberating photo-ionized quarks is that a high-resolution spectrometer (or related multi-channel device) can detect the well-defined X-rays emitted by the capture of the quark to a definite heavy atom (such as gold or thorium). 

On account of the long half-life of U , the problem of the activities of its daughter products becomes more severe each time the fuel is recycled through the reactor. One way in which the buildup of U can be reduced is by the physical separation of the fertile thorium from the fissile fuel in the reactor. The separation of the two by a significant thickness of moderator reduces the kinetic energies of most of the fission neutrons below the threshold of the (n, 2n) reaction in Th before they have the opportunity of reaching the fertile material. It is also necessary to limit the exposure of the fertile material, since the buildup of U will gradually supply a new source of fission neutrons in contact with the thorium. 

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