Three Mile Island Meltdown (Fall 2012)

The meltdown of reactor two of the Three Mile Island nuclear power plant was the worst accident in U.S. nuclear power plant history. Although only a small amount of radiation was leaked into the environment, this disaster had a huge impact on the U.S. nuclear power industry and the politics that go into nuclear power. It also caused about 2.4 billion dollars of property damage to the plant and its surrounding land.

So what was Three Mile Island like before the accident? It is a commercial nuclear power plant located on Three Mile Island in Pennsylvania. Contrary to popular belief, Three Mile Island is named this because it is three miles south of Middletown, PA, not because it is three miles long. The actual length of the island is a little over two miles. The plant has two separate reactors, named TMI-1 and TMI-2. The initial cost of the first reactor was 400 million dollars, with the second costing about 500 million because it was slightly bigger. The plant was designed by Babcock & Wilcox, built by the General Public Utilities Corporation in 1968, and was operated by the Metropolitan Edison Company (Met-Ed). After the investigation of the meltdown, it will later be determined that the main cause of the incident will be operator error which will cost Met-Ed over 84 million dollars in lawsuits and health claims. Despite the severe damage to TMI-2 from the accident, TMI-1 is still in commission today.

Now we move back in time to March 28, 1979, the date of the accident. At about 4:00am Eastern Time a failure happened in the non nuclear section of the plant. It is unknown what the cause of the failure was, but it resulted in the main water pumps failing to remove heat from the system. This causes an automatic failsafe to start, shutting down the reactor immediately. This caused the pressure in the reactor to rise. In order to avoid a rupture, a pilot-operated relief valve or PORV was opened to let out some pressure. This was protocol for high pressure. This valve would be the ultimate downfall of the system. After about ten seconds, the crew of TMI-2 sent a signal to the valve to shut it. The flaw in the system was that there was no actual sensor to tell that the valve actually closed. The valve in fact did not close, allowing coolant to escape through this valve.

This is the point at which we have to decide what is flawed; the operators of the reactor or the design. At this point, water is escaping out the PORV. In response to this, the system automatically pumped more water into the system to make sure the reactor stays cool. Of course this water flowed out the PORV also. After the water exited the PORV, it flowed into the pressure gauge. Another flaw in the system was that there was no real gauge of the coolant inside the reactor. This is when the operators decided to judge the amount of coolant in the reactor by looking at the level in the pressure gauge. Since it was high (due to the escaped coolant flowing into it), they thought the reactor had adequate coolant as well. Since they didn’t know the PORV didn’t close, this was how they were trained to operate the system. Then they made the decision that destroyed TMI-2; they reduced the amount of replacement coolant allowed into the reactor.

Once all cooling is stopped in a nuclear reactor, the core becomes super heated and starts to melt down. This is severe core meltdown, which is the worst possible disaster that can happen in a nuclear power plant. Once core meltdown began in TMI-2, the plant was is crisis. At 6:22am operators shut a block valve between the pressure gauge and the PORV, which stopped coolant from escaping the reactor. Normally this would have been the end of the issue. Since the coolant in the system was allowed to boil away and turn to super-heated steam, there was gas blocking the flow of new coolant entering the system, allowing the reactor to continue to meltdown. The only option left for the operators of TMI-2 was to continue to push high pressure pumps of water to try and collapse the bubbles of gas. It wasn’t until 7:50pm that this finally worked and they were able to restore adequate cooling for the reactor.

After the crew seemingly solved all the problems of the reactor meltdown, another one emerged; a bubble of hydrogen had been produced during the meltdown and was now a threat to burn or explode in the core chamber. This caused huge anxiety in the crew, fearing that an explosion could breach the containment building and release a huge amount of contaminant into the environment. This fear continued for a few days until April 1st when experts determined the bubble could not explode because there was no access to oxygen. Also by that time the bubble had reduced in size so that it was no longer a large threat. By the time this finally happened, they plant was highly contaminated. About 43,000 curies of radiation had been vented out of the reactor.

The health effects of the release of this radiation were very inconspicuous and virtually obsolete. The EPA and other major organizations have done many studies to determine if the radiation leaked would have any adverse effects on health, and each time they found that the most possible dose that any person living near the site could have received was 100 millirems. The average background radiation that one receives per year is about 120 millirems, so this would have no serious effects on health. The real damage that was caused by the accident was financial and political.

As you could guess, the cleanup was also a very important part of the TMI-2 meltdown. The process took over 12 years, starting in August 1979 and ending in December 1993. Everything in TMI-2 needed to be cleaned and about 100 tonnes (metric unit for 1,000 kilograms) of damaged uranium fuel had to be safely removed from the structure. The clean-up process cost approximately 1 billion U.S. dollars, making it the worst nuclear disaster in United States History. It also led to a lot of political problems down the road, along with environmental and technological ones as well.

The Three Mile Island nuclear meltdown had huge impacts on three historical forces: politics, technology, and economics. A large impact was caused by the economic force. In total, the construction, clean-up, and lawsuits cost the U.S. about 2.4 billion dollars. On the other hand, after the incident at Three Mile Island, 51 American reactors’ constructions were cancelled between 1980 and 1984. Of the 129 plants that had been approved at the time of the incident, only 53 were ever made. This incident severely slowed the nuclear industry down. Only the Chernobyl disaster would have a bigger impact on world nuclear power markets. On the other hand, this disaster created many new jobs in designing, testing, and operating safety protocols for nuclear power plants. Building and testing the plants took twice as long now to ensure securities and to triple check safety regulations, creating more labor hours. Although the incident originally hurt the economy to the tune of 2.4 billion dollars, in the end it created new jobs for some hard working Americans.

Another historical force that was greatly affected by the Three Mile Island disaster was the Technology force. It is obvious that many safety mechanisms on the TMI-2 reactor did not work very well. In order for a severe nuclear meltdown to happen, many things have to fail beforehand. The failure of these pieces of equipment led to a large amount of redesigning and strengthening all safety equipment, including safety valves and emergency cooling systems. It also led to the redesign of new technologies to automatically shut off plants if certain things go wrong, along with new specific gauges that will provide the correct information to the plant’s operators. In conclusion, the disaster led to a much safer and better designed nuclear power plant.

The largest historical force in play during the Three Mile Island disaster is the political force. After the meltdown, large protest groups gained a lot of power and credibility. The largest protest was in New York City in September 1979. Over 200,000 people attended, including Ralph Nader and Jane Fonda, who gave speeches to the protesters. These protests, along with the general need for new safety precautions, led to the creation of many committees and work groups in charge of overseeing nuclear power plant activity. These things include: a twenty-four hour Nuclear Regulatory Commission office that oversees all nuclear power plants, expansion of the NRC’s inspection program to provide daily checkups of the plants, creation of the Institute of Nuclear Power Operations, which is now the Nuclear Energy Institute, in order to look into generic nuclear issues, and expansion of the NRC’s international contact in order to spread the knowledge of nuclear power safety throughout the world. Although the political force was very positively influential during this time, confidence in nuclear power was at an all time low after the disaster.

Three Mile Island was the worst nuclear disaster to ever happen within the United States. Although this accident cost the U.S. over two billion dollars and the confidence of its people, many positive things came from this crisis, including new, safer regulations of nuclear power, new jobs in the industry, and new technology for use in running and inspecting these plants. Three Mile Island will be an event that is never forgotten, but will always be looked back on as a turning point in U.S. nuclear history. And if that isn’t enough good coming out of this incident for you, then go out and enjoy some Three Mile Island flavored wings at Hooters Restaurant. But be warned; they are just about as hot as TMI-2’s reactor was.

Sources

1. "Backgrounder on the Three Mile Island Accident." NRC:. United States Nuclear Regulatory Commission, 15 Mar. 2011. Web. 09 Dec. 2012.
2. "Meltdown at Three Mile Island." PBS. PBS, n.d. Web. 09 Dec. 2012.
3. "Three Mile Island Accident." Three Mile Island. World Nuclear Association, Mar. 2001. Web. 09 Dec. 2012.
4. "Three Mile Island Accident." Wikipedia. Wikimedia Foundation, 12 Sept. 2012. Web. 09 Dec. 2012.
5. "Three Mile Island." Encyclopedia.com. High Beam Research Inc, n.d. Web. 09 Dec. 2012.
6. "Three Mile Island Nuclear Generating Station." Wikipedia. Wikimedia Foundation, 12 Aug. 2012. Web. 09 Dec. 2012.
7. "Three Mile Island." Three Mile Island Alert. Unknown, n.d. Web. 09 Dec. 2012.