Chernobyl Unit 4 reactor

The Chernobyl Unit 4 reactor had the following principal specifications (IAEA, 1986) ... 

Certainly the most catastrophic nuclear accident occurred on April 26, 1986, at the Chernobyl unit 4 reactor near Kiev, Ukraine. The accident resulted in a core meltdown, explosion, and fire. 

In 1986, an accident occurred at the Chernobyl Unit 4 reactor near Kiev in Ukraine. The Chernobyl reactor was a light water-cooled graphite-moderated (LWG) reactor. This accident led to the release of a large amoimt of airborne radioactivity and the death of many of the responders. As a result of this accident, several countries with smaller nuclear power programs ceased the pursuit of nuclear power electricity generation. 

Nuclear weapons production and testing facilities (Hanford, WA, Savannah River, GA, Rocky Flats, CO, and The Nevada Test Site, in the United States, and Mayak in the former Soviet Union), also released small amounts. The releases occurred in accidents with nuclear weapons, the reentry of satellites that used Pu-238, and by the Chernobyl nuclear reactor accident. 

By approximately 11 00 pm Friday evening, the local electricity demand had subsided, and the load dispatcher gave permission for Chernobyl Unit 4 to continue with its power reduction. At this point, another step in a string of unfortunate events occurred when the automatic reactor control unit did not adjust for the new lower power level. The operators had reset the reactor monitoring system to the requested level, but had failed to reset the reactor automatic controller. The reactor s response was a dramatic drop in power, down to 30 MWt, 1 % of the normal operating level (US NRC, 1987). In effect, the automatic controller inserted control rods, which drove the overall core power dramatically lower than was intended. 

Nuclear power has achieved an excellent safety record. Exceptions are the accidents at Three Mile Island in 1979 and at Chernobyl in 1986. In the United States, safety can be attributed in part to the strict regulation provided by the Nuclear Regulatory Commission, which reviews proposed reactor designs, processes appHcations forUcenses to constmct and operate plants, and provides surveillance of all safety-related activities of a utiUty. The utiUties seek continued improvement in capabiUty, use procedures extensively, and analy2e any plant incidents for their root causes. Similar programs intended to ensure reactor safety are in place in other countries. 

The fear of accidents like Chernobyl, and the high cost of nuclear waste disposal, halted nuclear power plant construction in the United States m the 1980s, and in most ol the rest ol the world by the 1990s. Because nuclear fusion does not present the waste disposal problem of fission reactors, there is hope that fusion will be the primary energy source late in the twenty-first centuiy as the supplies of natural gas and petroleum dwindle. 

While we recognize the major concern attendant on widespread use of nuclear power in particular reactor malfunction, we note that no reactor accident that harmed any member of the public has occurred in any facility meeting international safety standards (Chernobyl did not meet the standards). Eossilfuel pollution from power plants is estimated to cause 40,000 to 70,000 deaths per year in the United States alone. 

The past safety record of nuclear reactors, other than the Soviet Chernobyl-type RBMK reactors, is excellent Excluding RBMK reactors, there had been about 9000 reactor-years of operation in the world by the end of 1999, including about 2450 in the United States.1 In this time there was only one accident involving damage to the reactor core, the 1979 Three Mile Island accident, and even at TMI there was very little release of radionuclides to the outside environment. 

Three Mile Island and Chernobyl occurred more than 20 years ago and the nuclear power freeze is beginning to thaw. High priced oil and natural gas make atomic energy appear cheap by comparison. Global-warming concerns are pushing a new interest in nuclear power. After a decade where no nuclear power plants came online in the United States, 31 new reactors are planned. 

Lithuania is more dependent on nuclear power than any other country in the world. Its two 1500-megawatt reactors produce more than 80 percent of the country s electricity. The reactors, however, are the same design as the unit that caused the Chernobyl disaster. With both reactors working, Lithuania can produce almost twice as much energy as its domestic demand, allowing the country to sell the excess to other nations. If one unit were shut down, however, the country... 

Everyone s worst fears about nuclear power became a reality in tlie later part of April 1986. A large Soviet reactor - unit number 4 at Chernobyl, 80 utiles nortli of Kiev, and only 3 years old blew out and burned, spewing radioactive debris over much of Europe. Radiation levels increased from Sweden to Britain, tlirough Poland, and as far soutli as Italy. The damage caused to tlie environment far surpassed tlial due to tlie accident at Tliree Mile Island. 

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