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How A Nuclear Reactor Works

March 16, 2011 by staff 

How A Nuclear Reactor Works, As Japanese nuclear engineers struggled to contain partial collapse of two large nuclear reactors after an earthquake and tsunami, experts from the United States said Sunday that a similar disaster would be very unlikely here.

The hydrogen gas exploded today in one of the reactors under threat – the second such explosion to plague scientists trying to neutralize the danger to the plant in Fukushima Dai-ichi Nuclear. But authorities later said inner enclosure holding the nuclear fuel rods remained intact.

Japanese reactors – such as those from America – are built to withstand the ground shaking from earthquakes. But on Friday one to two punch of an earthquake of 8.9 magnitudes and a tsunami was almost overwhelming power plant operators there.

Fifty-four power reactors regular supply of electricity throughout Japan, and the crisis is “an extremely rare disaster worst case,” said Jasmina Vujic, professor of nuclear engineering at UC Berkeley and a specialist in the design reactor core and radiation protection.

At the plant of Dai-ichi, workers desperate to cool overheated reactor cores flooded with seawater reactors, creating steam and pressure that had to be evacuated. The process of escape of small amounts of radiation. And it has created favorable conditions for an explosion because the water vapor contains hydrogen, which can ignite when it comes into contact with oxygen outside the reactor chamber.

The authorities ordered, 000 people evacuated areas around the plants in trouble, but it is unknown how many were exposed to radiation and what danger they face. Vujic note that while the levels of radiation dose fall by one million times less than a mile – about half a mile – a radioactive source.

Nuclear plants in the United States do not face the dangers facing Japan, according to experts. Even huge tsunamis are not likely to threaten the reactor sites in the country, while the earthquakes as large as Japan are not planned across America – not even on the San Andreas Fault or Hayward.

Nor does the central Diablo Canyon nuclear power, 235 miles south of San Francisco on the coast near San Luis Obispo, are harmful as those facing Japan, “said Paul Flake, a spokeswoman for Pacific Gas and Electric Co. The company operates the plant both pressurized water reactors, which were built by Westinghouse in and 1986.

The plant is located above the ocean near Avila Beach, and pumps its cooling water from the Pacific Ocean. If the pumps fail, the pools of water standing near the factory and can cool the reactor by gravity, Flake said, citing engineers at the plant.

Four plants have been damaged in Japan, with the most severe impact in the complex of Dai-ichi Nuclear in northern Japan, where the quake struck at all power supplies and tsunami of 30 feet flooded the emergency generators.

On Sunday, he was already the worst nuclear disaster since the Chernobyl reactor in Ukraine; former Soviet Union exploded and burned, sending a plume of radiation across Europe.

The complex has six reactors Fukushima, and operators, there was an attempt to cool the reactor core overheating in Units and 3 in the flooding of sea water but it was hard work but unable, and fire trucks were mobilized to pump water into the pressure chambers of the reactor, Vujic said, citing conversations with colleagues in Japan. The hydrogen explosions hit two of these units.

A third plant in Fukushima was also in trouble, Japanese officials said, and a state of emergency was declared on three more units in the complex near Fukushima Daini.

Officials said that although partial collapse was feared least two units of the complex Dai-ichi, none of the reactors was near the edge of collapse. If the fuel rods in the reactors will not melt completely, they would severely damage the entire reactor and contaminate them with radioactivity.

However, in a nuclear power plant, each reactor is housed in a containment dome, very powerful, built of thick concrete embedded with a network of heavy steel rods. All Japanese nuclear power plants in trouble – because they were designed to survive earthquakes – were still harboring reactors on Sunday.

United States, domes as strong as those are also constructed to contain all the reactors.

Japan’s nuclear crisis is not equal to the Chernobyl disaster years ago in the former Soviet Union, where a core set of the reactor exploded. More than 350,000 people who lived near the plant were evacuated and relocated.

It was the worst nuclear accident in history, but the plant has no containment dome of protection over it. Subsequently, the Soviet Union buried in the ruins of the reactor structure in concrete.

Single nuclear accident in America, at Three Mile Island in Pennsylvania, took place in 1979 when a stuck valve caused the coolant to escape from the heart of the reactor and trigger partial melting. The accident was quickly extinguished. A unit of the plant remains closed, while another took over the farm in 1985 and still works.

Source: http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/03/14/MNAJ1IA9CF.DTL

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