1 result for (book:deavf2 AND session:941 AND stemmed:engin)
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In Note 2 for the 936th session, I also described how the NRC had asked the operators of certain nuclear power plants to check for cracks in the vessel walls of their pressurized-water reactors, which are the kind installed at TMI. Now problems with corrosion are being announced. The reactor for Unit No. 1 at TMI is undamaged; it had been shut down for maintenance and refueling at the time of the accident to its twin, nearly three years ago, and a series of delays has kept it idle ever since. In February, again, company officials revealed the discovery of extensive corrosion in the bundles of small-diameter tubes in the two steam generators powered by Unit No. 1, which will delay any restarting of the unit for another six months to a year. The tubes circulate hot radioactive water from the reactor throughout the steam generators. Replacement of at least several thousand such tubes will cost millions of dollars; if engineers simply plug the damaged tubes, the reactor will operate well below capacity. (Steam generators at some other plants have a new problem: the accumulation of a corrosive sludge at their bases.)
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Company projections are that the entire cleanup at TMI won’t be completed until the end of 1988—more than nine years after the accident took place. Current plans are that once the radioactive water is drained from the containment building of Unit No. 2, engineers will conduct remote investigations of the core of the reactor itself. A specially designed video camera will be inserted into the core so that the actual damage to the pencil-thin fuel rods can be assessed; and hundreds of thousands of sonar readings, taken through openings already present in the reactor, will be assembled by computer into images of the core. Several major steps must follow, all of them on an enormous scale: the lifting of the 160-ton metal “head,” or cap, of the reactor; the removal of the upper plenum assembly, the 55-ton mechanism which makes possible the raising and lowering of fuel control rods into the 100-ton reactor core, thus regulating the intensity of its nuclear reactions; and eventually, the difficult piece-by-piece removal of the damaged core itself. Even then, the core will still be so radioactive that most of the work will have to be done by remote-controlled devices. Finally, the cavernous containment building itself will be cleaned, again by remote control.
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