Word: reactors
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...first known nonmedical Westerner to meet with those hospitalized by the disaster. Accompanied by Gale, Hammer visited Kiev's Hospital 14, where 259 Chernobyl victims have been treated, and talked with two heroes, S.T. Milgevsky and N.E. Fedorenko, bus drivers who ferried firemen and workers to and from the reactor area after the explosion. Why did they do it? Hammer asked. "Someone had to," they replied. Would they do it again? "Sure." Hammer also met V.D. Dznenko, who had been visiting her daughter in the area at the time of the accident. Afterward Hammer and Gale took a low-altitude...
...long as a coolant (water in most reactors) keeps flowing around the reactor core, it carries heat away, and the temperature stays under control. If the coolant is lost, the core begins to overheat, like a car with a broken radiator. The chain reaction promptly ceases because rising temperatures cause the fuel to expand, which increases the distances between individual atoms and makes it less likely that the neutrons emitted by one will hit the nucleus of another. But the spontaneous radioactive decay of nuclei goes on. The uncooled reactor core could eventually get hot enough to melt through...
...MHTGR, in contrast, has no safety cooling system at all; the helium gas flowing through its core merely carries away heat to power electric generators. The reactor itself can never get hot enough to melt down. In the MHTGR, bits of uranium fuel are encapsulated in tiny grains made of carbon and silicon compounds. The fuel particles, which are embedded in racquetball-size "pebbles" of graphite, will remain intact up to 3600 degreesF. But the configuration of the core and the reactor's size (it generates only 80 megawatts of power, compared with 1,000 megawatts for large conventional reactors...
...already had a bit of experience with gas reactors. Philadelphia Electric Co. successfully tested a 40-megawatt experimental version from 1967 to 1974. However, the Fort St. Vrain plant, 35 miles north of Denver, has had one breakdown after another during the decade since it began operation. But Lidsky points out that the plant is so big -- 330 megawatts -- that it needs as complex a cooling system as conventional plants. The reactor's large size, he says, has caused most of the trouble...
...What is needed," Lidsky concludes, "is a reactor that Dan Rather can shoot with a bazooka on-camera, and it shuts down without releasing radioactivity. That is what the MHTGR...