Meltdown, nuclear

CHINA SYNDROME. A term referring to a catastrophic accident in which a nuclear reactor core melts through the containment of a nuclear power plant and metaphorically burns its way downward through the Earth from the United States to China. American physicist Roger S. Boyd claimed to have coined the phrase in the early 1960s while he was working for the U.S. Atomic Energy Commission (AEC). See also MELTDOWN NUCLEAR PILE. 

Tlie advances of modern teclmology have brought about new problems. Perliaps tlie most serious of these is tlie tlireat of a nuclear power plant accident known as a meltdown. In tliis section several of tliis era s most infamous accidents are examined some possible explanations are also offered. 

The most serious accident tliat Ciui occur in a nuclear plant is a reactor core meltdown. In a core meltdown, the enclosed gases physically melt through tlie reactor vessel, and once contacting with cooler liquids or vapors either in a cooling jacket or in the outer enviromnent, cause a physical e. plosion to occur. However, tlie hazard caused by the e. plosion itself is minimal and more localized compared with the release of radioactive material that accompanies such an accident. 

A much more serious nuclear accident occurred at Chernobyl in the USSR on April 26, 1986, when one of the Chernobyl units experienced a full-core meltdown. The Chernobyl accident has been called the worse disaster of the industrial age. An area comprising more than 60,000 square miles in the Ukraine and Belarus was contaminated, and more than 160,000 people were evacuated. However, wind and water have spread the contamination, and many radiation-related illnesses, birth defects, and miscarriages have been attributed to the Chernobyl disaster. 

Nuclear power plants in the United States are supposed to be designed well enough to prevent accidents as serious as the one at Chernobyl. Nevertheless, the Three Mile Island plant in Pennsylvania, an aerial view of which is shown in Figure 22-14Z). experienced a partial meltdown in 1979. This accident was caused by a malfunctioning coolant system. A small amount of radioactivity was released into the environment, but because there was no explosion, the extent of contamination was minimal. 

Eisler, R. 1995. Ecological and toxicological aspects of the partial meltdown of the Chernobyl nuclear plant reactor. Pages 549-564 in D.J. Hoffman, B.A. Rattner, G.A. Burton, Jr., and A.J. Cairns, Jr. (eds.). Handbook of Ecotoxicology. Lewis Publ., Boca Raton, FL. 

Causing a nuclear reactor meltdown after taking over the control room... 

Besides the aluminum industry, the nuclear power industry has been interested in molten aluminum-water explosions due to the presence of aluminum metal in some boding water reactors. Certain accident scenarios lead to a meltdown of the reactor core with concomitant contact of molten aluminum and water. 

The battle over nuclear power waxed hot and heavy for several years, swaying back and forth as incidents unfolded. The publication of the government-sponsored Reactor Safety Study in 1975, which showed that there would be very modest consequences from nearly all reactor accidents, was a positive event. The report concluded that the average number of fatalities from a meltdown would be about 400 and that there might be one meltdown in every 20,000 years of plant operation, or 0.02 deaths per year versus about 25 deaths per year due to air pollution from a coal-burning plant.8 It received little notice outside the scientific community. The movie The China Syndrome (released in 1979), which implied that a reactor meltdown accident would have— not possibly might have—very horrible consequences, was an important negative event. 

In 1986, a meltdown occurred at this nuclear power plant in Chernobyl, Ukraine. Because there was no containment building, large amounts of radioactive material were released into the environment. Three people died outright, and dozens more died from radiation sickness within a few weeks. Thousands who were exposed to high levels of radiation stand an increased risk of cancer. Today, 10,000 square kilometers of land remain contaminated with high levels of radiation. 

No The worst-case scenario for a nuclear power plant is the meltdown, which occurs as an uncooled nuclear reactor gets so hot that it melts to the floor of the containment building. Nuclear fuel is enriched with fissionable uranium-235 to at most 4 percent. The remainder of the fuel is nonfissionable uranium-238. As discussed in Chapter 4, to build a nuclear bomb, uranium-235 must be enriched to over 90 percent. 

By the 1970s, nuclear power was in widespread use, in the U S. and abroad, as a source of electricity. As of 2007, nuclear power provided about 19.3% of the electricity generated in the U.S., created by 104 licensed nuclear reactors. Nonetheless, the potential for accidents, meltdowns and other disasters has never been far from the minds of many consumers (after all, for many of us the first image that comes to mind upon hearing the word nuclear is a nuclear bomb). The 1979 Three Mile Island nuclear power plant accident in the U.S. led to the cancellation of scores of nuclear projects across the nation. This trend was later reinforced by the disaster at... 

Chernobyl in what was then the Soviet Union. Regulatory agencies took an even harder line on U.S. nuclear power plants, and the popular movie The China Syndrome highlighted the terrifying possibility of human error and hubris leading to a nuclear power plant meltdown on the California coast. 

The anthropogenic radionuclides of most concern are those produced as fission products from nuclear weapons and nuclear reactors. The most devastating release from the latter source to date resulted from the April 26, 1986, explosion, partial meltdown of the reactor core, and breach of confinement structures by a power reactor at Chernobyl in the Ukraine. This disaster released 5 x 107 Ci of radionuclides from the site, which contaminated large areas of Soviet Ukraine and Byelorussia, as well as areas of Scandinavia, Italy, France, Poland, Turkey, and Greece. Radioactive fission products that are the same or similar to elements involved in life processes can be particularly hazardous. One of these is radioactive iodine, which tends to accumulate in the thyroid gland, which may develop cancer or otherwise be damaged as a result. Radioactive cesium exists as the Cs+ ion and is similar to sodium and potassium in its physiological behavior. Radioactive strontium forms the Sr2+ ion and substitutes for Ca2+, especially in bone. 

Nuclear power plants are designed to prevent accidents such as meltdown by careful control of fuel-rod placement and positioning of control rods made of boron or other materials that have high affinity for neutrons. If the core of the reactor should become overheated, the fuel rods are... 

In the past only two nuclear accidents (Three Mile Island and Chernobyl) were widely reported, while over 100 went unreported. These other accident were not caused by only earthquakes, design errors or terrorist acts, but more recently also by software virus attacks through the Internet. For example, on January 25, 2003 a Slammer worm penetrated the private computer network of Ohio s Davis-Besse nuclear power plant, and stopped its control computer. The only reason a meltdown did not result is because the plant was not in operation. 

Gas explosion in transit caused 100 deaths and 150 injuries One of two reactors lost its coolant, which caused overheating and partial meltdown of its uranium core. Some radioactive water and gases were released. This was the worst nuclear-reactor accident in U.S. history... 

The primary source of radionuclides produced in the fission process and found in the environment is atmospheric testing of nuclear weapons. The public has been exposed to these and other radionuclides for five decades, but there has been a substantial decline in atmospheric testing in the past two decades. Therefore the major source of fission product radionuclides in recent years has been from nuclear accidents. A nuclear reactor meltdown could release a spectrum of radionuclides similar to that of a nuclear bomb explosion, but the ratios of nuclides would greatly differ for the two cases. The reason for the differences in ratios of radionuclides is that during the reactor operation the long-lived radionuclides tend to build up progressively, whereas the... 

Nuclear powered ship/submarine reactor meltdown... 

Neptunium is used in nuclear reactors. Pictured here is Three Mile Island in Middletown, Pennsylvania, site of a partial meltdown in 1979- IMAGE COPYRIGHT 2009, DOBRESUM. USED UNDER LICENSE FROM SHUTTERSTOCK.COM. 

People exposed to a single large dose or a few large doses of radiation in a short period of time are said to have experienced an acute radiation exposure. More than 230 people suffered acute radiation sickness and 28 died when a meltdown occurred in 1986 at the Chernobyl nuclear power plant in the Ukraine. 

The risks associated with the operation of nuclear reactors are small but not negligible, as the failnre of the Three Mile Island reactor in the United States in 1979 and the disaster at Chernobyl in the former Soviet Union in 1987 demonstrated. If a reactor has to be shnt down quickly, there is danger of a meltdown, in which the heat from the continning fission processes melts the uranium fuel. Coolant mnst be circulated until heat from the decay of short-lived isotopes has... 

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