Word: reactors
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...been anticipated in engineering studies. Said Dudley Thompson, an executive officer of the NRC: "We are in a situation that is not a situation we have ever been in before." As officials studied the complex hazard, they discovered yet another ominous possibility: if the amount of hydrogen in the reactor kept growing, it could reach a level at which only a spark would be needed to set off a hydrogen-gas explosion. If the explosion were powerful enough, the core vessel might rupture and the concrete walls of the container building might break, exposing the surrounding area to the reactor...
Various ways of eliminating the problem were considered by the increasingly anxious engineers. One was to try burning off the hydrogen under controlled circumstances. The second was to gradually raise the pressure inside the reactor to the point that the hydrogen would dissolve in the water at the bottom of the reactor room. The third choice was to lower the water level at the floor of the reactor room and pour fresh water in from the top, thus pushing the bubble toward the bottom and away from the fuel rods. Another possibility was to restart the reactor, generating heat...
...Sunday, the President helicoptered from Washington to visit the ailing plant. The former navy nuclear engineer toured the control room, was briefed by the experts in charge of solving the reactor problems and afterward issued a reassuring statement. Even if an evacuation is ordered of the Three Mile Island area, Carter said, "This will not indicate that danger is high. It will be strictly a precautionary measure...
...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...
...slightest hint of trouble, the reactor's computer is programmed to drop the control rods back into the core. That curtails the core's chain reaction, but heat is still given off. If the core's temperature rises precipitously as a result of the problem, possibly a loss of cooling fluid (a "blowdown"), the computer will activate an emergency core cooling system. That system should quickly dump thousands of gallons of water on the hot core, preventing what has become known as a "meltdown," in which the fuel melts through the floor of the containment building into...