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On the anniversary of Three Mile Island nuclear accident known worse in US territory, we give an overview of what happened that fateful day in 1979.
Four years have passed, but many still remember the earthquake 2011 in Japan, which was mainly a result of the accident at the nuclear power plant Fukushima . This accident ended up becoming one of the most serious on the scale INES (International Nuclear Event Scale), coming to Level 7 , something only equaled at the time the accident Chernobyl in the former Soviet Union.
But an accident does not reach the level 7 does not mean it is not serious and damaging to both the environment and the living beings surrounding such accident. Throughout our history we have seen several of these accidents such as Kyshtym disaster in the Soviet Union, the Windscale fire in the UK, the reactor accident RA-2 in Argentina, or incident Vandellos in Spain. However, today we focus on the accident at Three Mile Island , which stands out as the largest nuclear accident in US history .
March 28, 1979 thirty-six years ago was a day like any other in the state of Pennsylvania: Jimmy Carter was still President pending suffer a resounding defeat against Ronald Reagan, Tragedy Bee Gees was successful time as if it were a macabre joke, the film China Syndrome took twelve days at the box office telling the story of some reporters (played by Jane Fonda and a young Michael Douglas) covering a nuclear accident. However, about four o’clock that day, a series of irregularities that March 28 became a day to forget in the history of nuclear development.
The nuclear power plant at Three Mile Island was composed two reactors had little time in operation, with the TMI-1 entered service on 19 April 1974 and his brother, the TMI-2, coming on stream in December 1978 (ninety days before the accident). In fact, it was the TMI-2 accident catalyst since the TMI-1 was being held at that time by refueling, and be separate facilities, there was no effect domino affect the other reactor. This part is important, as having been connected, the environmental disaster could have been much worse.
Even without direct victims, Three Mile Island is considered one of the most serious nuclear accident in history. It all started when there was a mechanical or electrical failure (today could not be determined) in the secondary circuit of the plant, causing their feed pumps stop working, preventing the heat steam generator primary system dissipate . As a security measure, the first turbine and then the reactor is shut down automatically, while the temperature and pressure of the primary circuit is started to increase immediately due to the breakdown of the abovementioned secondary system.
Therefore, and to release said pressure relief valve was open, but managed to reduce it, did not close when he finished his work as it should have done, and the indicator that warned the operator no indication of any state of said valve . Consequently, faulty valve caused the pressure to continue declining in the system to be below acceptable limits. So far all these faults were mechanics and, although you could be held accountable for it, operators had acted properly.
But another problem to arise was when operators were unable to tackle the problem. And the emergency water system of the secondary system, responsible for cooling the steam generator primary system, was used two days before before the accident in a test in which the valve closes allows operation. However, due to an administrative error or personal , said valve is not left open at the end of the test so it did not work properly, and operators of Three Mile Island it took eight minutes from start the accident to realize that the valve was closed.
Once the valve is open, the emergency water system began to work correctly, allowing the cold water flow through steam generators. As the pressure was falling, vapor bubbles formed by boiling water caused a water distribution within the system, transferring all the water inside the pressurizer and leaving the rest of the system with steam . Then the indicator that informs the operator about the amount of coolant able to remove heat incorrectly indicated that the system was full of water, so he stopped introducing water.
The mixture of human error and mechanical problem became an environmental disaster. More than two hours after the first incident of this chain, the top of the reactor was exposed. The reason? The vapor within the system blocked the flow in the system, and said blocking circulation system caused the water remaining inside the system could not get out and become more steam, greatly increasing the pressure. To be the top pool, the fuel pellets are released into the coolant and generated hydrogen, prompting a small explosion in the containment building upon release.
With the shift change at the Three Mile Island began to change things for the better, although the consequences in those two hours had been terrible. The new team proceeded to close an auxiliary valve that had left out one hundred and twenty thousand liters of contaminated cooling water main circuit. Such water activated alarms radiation detectors once reached. At that time the radiation levels in the coolant was a 300 times higher than expected levels , and the center was already a serious problem of pollution, contaminated water leaked from the concrete of the building, leaving impossible to remove radioactive waste.
In addition, the control room was not known that about half of the core was without refrigeration, and it was not until eleven o’clock when he began injecting fresh water the primary circuit to be cooled, which came late to prevent a hydrogen explosion that had continued to generate inside the reactor unnoticed. Finally, at sixteen hours primary circuit pumps were launched and core temperature began to drop , but the effects of radioactive fuel had left terrible effects in the reactor: a large part of the core had already melted or vaporized, and the system was still dangerously radioactive
Yes, Three Mile Island narrowly escaped a meltdown , but environmental and social consequences were disastrous. Although there were direct victims of the accident, over the next week between 2.5 and 15 million curies in radioactive steam and hydrogen were evacuated from pouring reactor directly to the atmosphere, to which Greenpeace has repeatedly stated that existed and There is a clear increase in cases of cancer and leukemia on near the central area.
Socially, this accident also moved many waters. There were numerous anti-nuclear demonstrations across the planet, whose arguments were reinforced after Chernobyl, and for a time the utility of nuclear power plants were questioned, especially if entailed run a big risk. However, Three Mile Island also served to establish a security protocol tighter and better instruct the operators of nuclear facilities, standards today are still maintained and have helped make the safest nuclear power plants, but were measures deblace taken following TMI, listed by INES Level 5 .
What happened to TMI For the decontamination of the central lasted over 14 years, between 1985-1995 and nearly 100 tons of nuclear fuel, which was stored as nuclear waste safely removed. The TMI-1 reactor remained standing until 1985 and the TMI-2 is in a status to “secure long-term storage.” Currently the TMI-1 is still running and while waiting to be dismantled in 2014, his license was renewed until 2034, all with a series of safety tests had to first pass, which makes sense because of his background.
March 28, 2015
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