Three Mile Island clean-up crew (October 1979). From: Report of The President's Commission on the Accident at Three Mile Island: The Need for Change: The Legacy of TMI. Image Source: Wiki.
Yesterday, I coincidentally heard someone in a shop say: 1979 was a good year. It wasn't a good year in Pennsylvania. Today is the 33rd anniversary of the Three Mile Island nuclear disaster, the worst meltdown in American history. This partial meltdown at Reactor 2, which arose due to design and operator errors and a loss of coolant, led to radioactive gases and iodine being released into the atmosphere. The United States Nuclear Regulatory Commission explains what happened during the accident (here):
The accident began about 4:00 a.m. on March 28, 1979, when the plant experienced a failure in the secondary, non‑nuclear section of the plant. The main feedwater pumps stopped running, caused by either a mechanical or electrical failure, which prevented the steam generators from removing heat. First the turbine, then the reactor automatically shut down. Immediately, the pressure in the primary system (the nuclear portion of the plant) began to increase. In order to prevent that pressure from becoming excessive, the pilot-operated relief valve (a valve located at the top of the pressurizer) opened. The valve should have closed when the pressure decreased by a certain amount, but it did not. Signals available to the operator failed to show that the valve was still open. As a result, cooling water poured out of the stuck-open valve and caused the core of the reactor to overheat.
As coolant flowed from the core through the pressurizer, the instruments available to reactor operators provided confusing information. There was no instrument that showed the level of coolant in the core. Instead, the operators judged the level of water in the core by the level in the pressurizer, and since it was high, they assumed that the core was properly covered with coolant. In addition, there was no clear signal that the pilot-operated relief valve was open. As a result, as alarms rang and warning lights flashed, the operators did not realize that the plant was experiencing a loss-of-coolant accident. They took a series of actions that made conditions worse by simply reducing the flow of coolant through the core.
Because adequate cooling was not available, the nuclear fuel overheated to the point at which the zirconium cladding (the long metal tubes which hold the nuclear fuel pellets) ruptured and the fuel pellets began to melt. It was later found that about one-half of the core melted during the early stages of the accident. Although the TMI-2 plant suffered a severe core meltdown, the most dangerous kind of nuclear power accident, it did not produce the worst-case consequences that reactor experts had long feared. In a worst-case accident, the melting of nuclear fuel would lead to a breach of the walls of the containment building and release massive quantities of radiation to the environment. But this did not occur as a result of the three Mile Island accident.
... By the evening of March 28, the core appeared to be adequately cooled and the reactor appeared to be stable. But new concerns arose by the morning of Friday, March 30. A significant release of radiation from the plant's auxiliary building, performed to relieve pressure on the primary system and avoid curtailing the flow of coolant to the core, caused a great deal of confusion and consternation. In an atmosphere of growing uncertainty about the condition of the plant, the governor of Pa., Richard L. Thornburgh, consulted with the NRC about evacuating the population near the plant. Eventually, he and NRC Chairman Joseph Hendrie agreed that it would be prudent for those members of society most vulnerable to radiation to evacuate the area. Thornburgh announced that he was advising pregnant women and pre-school-age children within a 5-mile radius of the plant to leave the area.
Within a short time, the presence of a large hydrogen bubble in the dome of the pressure vessel, the container that holds the reactor core, stirred new worries. The concern was that the hydrogen bubble might burn or even explode and rupture the pressure vessel. In that event, the core would fall into the containment building and perhaps cause a breach of containment. The hydrogen bubble was a source of intense scrutiny and great anxiety, both among government authorities and the population, throughout the day on Saturday, March 31. The crisis ended when experts determined on Sunday, April 1, that the bubble could not burn or explode because of the absence of oxygen in the pressure vessel. Further, by that time, the utility had succeeded in greatly reducing the size of the bubble.
Three Mile Island is classed on the International Nuclear Event Scale as a level 5 incident, that is, an accident with wider consequences. In terms of seriousness, it is on par with the UK's Windscale incident and Canada's first Chalk River episode.
140,000 pregnant women and pre-school age children were evacuated. Wiki has a comment that in the aftermath, the health effects, according to official inquiries, were negligible: "The Kemeny Commission Report concluded that 'there will either be no case of cancer or the number of cases will be so small that it will never be possible to detect them. The same conclusion applies to the other possible health effects.'" The clean-up lasted from August 1979 to December 1993 and cost $1 billion.
This disaster might be classified as something that could have become Chernobyl, but thankfully did not (read more here). The accident occurred a week and a half after the film, The China Syndrome, was released, which coincidentally depicted a similar meltdown. The film explored the inevitable cover-ups and public lies which surround nuclear incidents. The China Syndrome is the catastrophe now feared, possibly three times over, at Fukushima. There is a tamer estimation comparing Fukushima and Chernobyl, here; and a list of worldwide nuclear and radiation accidents here.
See all my posts on Nuclear themes.
Modern Marvels: Three Mile Island © History Channel. Video Source: Youtube.
140,000 pregnant women and pre-school age children were evacuated. Wiki has a comment that in the aftermath, the health effects, according to official inquiries, were negligible: "The Kemeny Commission Report concluded that 'there will either be no case of cancer or the number of cases will be so small that it will never be possible to detect them. The same conclusion applies to the other possible health effects.'" The clean-up lasted from August 1979 to December 1993 and cost $1 billion.
Meltdown at Three Mile Island (Part 1). Video Source: Youtube.
Meltdown at Three Mile Island (Part 2). Video Source: Youtube.
Meltdown at Three Mile Island (Part 3). Video Source: Youtube.
Meltdown at Three Mile Island (Part 4). Video Source: Youtube.
Meltdown at Three Mile Island (Part 5). Video Source: Youtube.
Meltdown at Three Mile Island (Part 6). Video Source: Youtube.
This disaster might be classified as something that could have become Chernobyl, but thankfully did not (read more here). The accident occurred a week and a half after the film, The China Syndrome, was released, which coincidentally depicted a similar meltdown. The film explored the inevitable cover-ups and public lies which surround nuclear incidents. The China Syndrome is the catastrophe now feared, possibly three times over, at Fukushima. There is a tamer estimation comparing Fukushima and Chernobyl, here; and a list of worldwide nuclear and radiation accidents here.
The China Syndrome Trailer (1979) © Columbia Pictures. Video Source: Youtube.
1993 Eco Documentary challenging government claims that Three Mile Island did not have significant environmental after-effects. Video Source: Youtube.
See all my posts on Nuclear themes.
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I was 9 years old. I don't remember much. A little, but not much. Maybe I deliberately suppressed it. -J
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