Word: cadmium
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...nuclear reactor, such a chain reaction is kept under control by "absorbers"-usually boron or cadmium rods. These capture neutrons that might otherwise split more atoms. But if the fissile material is pure enough, and sufficiently compressed, as in a bomb, the chain reaction speeds up. Heat accumulates, and the material blows apart to produce the nuclear age's familiar mushroom cloud...
...others turned out to be relatively pure. The biggest polluters, not surprisingly, are France, Italy and Spain. Thus they will have to bear the biggest part of the cost of the more than $10 billion program. The proposed treaty includes a blacklist of banned substances (for example, mercury, cadmium, radioactive materials) and a gray list of those that will be tolerated in specified quantities. All factories and sewage systems will be required to install antipollution devices, and new installations will have to conform to treaty specifications...
...catch these particles, the physicists placed a sealed container of deuterium, or heavy water, 11.2 meters (37 ft.) from the reactor. Immersed in the liquid were ten helium-filled tubes wired to an external oscilloscope. The detection apparatus was shielded in lead and cadmium cylinders and a foot-thick "pot" to block everything but neutrinos. As the particles barreled through the heavy water, some scored bull's-eye hits on the nuclei of its hydrogen atoms, which contain an extra neutron. These collisions produced other particles, including more neutrons that struck the helium-filled tubes and registered...
...reactor's power center is its fuel core. Housed in a pressure-cooker-like reactor vessel, the core is filled with pellets of fissionable uranium packed in bundles of thin cylindrical zircaloy rods. Inserted into the core are still other rods, usually made of cadmium or boron, which absorb and retain neutrons given off by the uranium atoms-in effect, stopping the billiards and regulating the intensity of the reaction. To start the reactor, the control rods are raised to precisely calculated levels. The chain reaction begins, converting mass into energy and producing great quantities of heat...
Photovoltaic cells made of silicon or cadmium sulfide, which can convert sunlight directly into electricity. Costs are very high, and existing installations are still only experimental...