Three Mile Island Nuclear Generating Station facts for kids
Quick facts for kids Three Mile Island Nuclear Generating Station |
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The Three Mile Island NPP on Three Mile Island, circa 1979
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| Country | United States |
| Location | Londonderry Township, Dauphin County, Pennsylvania |
| Coordinates | 40°9′14″N 76°43′29″W / 40.15389°N 76.72472°W |
| Status | B |
| Construction began | Unit 1: May 18, 1968 Unit 2: November 1, 1969 |
| Commission date | Unit 1: September 2, 1974 Unit 2: December 30, 1978 |
| Decommission date | Unit 1: September 20, 2019 Unit 2: March 28, 1979 |
| Construction cost | $1.557 billion (2007 USD) ($2.00 billion in 2021 dollars ) |
| Owner(s) | Unit 1: Exelon Unit 2: FirstEnergy |
| Operator(s) | Exelon Nuclear |
| Website Three Mile Island |
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The Three Mile Island Nuclear Generating Station (often called TMI) was a nuclear power plant located on Three Mile Island. This island is in Londonderry Township, Pennsylvania, right on the Susquehanna River. It's just south of Harrisburg.
The plant had two main parts, called units: TMI-1 and TMI-2. TMI-2 was the site of the most important accident in U.S. commercial nuclear energy. This happened on March 28, 1979, when TMI-2 had a partial meltdown. A meltdown is when the core of a nuclear reactor gets too hot and starts to melt.
However, a report from the Nuclear Regulatory Commission (NRC) said that no one was hurt or died because of the accident. This includes both plant workers and people living nearby. Later studies also found no link between the accident and any cases of cancer.
The core of TMI-2 was later removed from the site. Three Mile Island got its name because it is located three miles downriver from Middletown, Pennsylvania.
Contents
Understanding Three Mile Island
Three Mile Island was a place where electricity was made using nuclear power. It had two large units, TMI-1 and TMI-2. These units used a special type of reactor called a pressurized water reactor.
Unit 1 was owned by a company called Exelon Generation. Unit 2 was owned by FirstEnergy Corp. Unit 1 stopped making power in 2019. Unit 2 has been shut down since the accident in 1979. It is expected to be fully closed down around 2036.
Safety Zones Around the Plant
To keep people safe, the NRC set up two special zones around nuclear power plants. These are called emergency planning zones.
- The first zone is about 10 miles wide. It focuses on protecting people from breathing in any radioactive contamination that might be in the air.
- The second zone is about 50 miles wide. It focuses on making sure food and drinks are not contaminated by radioactivity.
In 2010, about 211,261 people lived within 10 miles of Three Mile Island. About 2,803,322 people lived within 50 miles. Cities like Harrisburg, York, and Lancaster are all within 50 miles of the plant.
Three Mile Island Unit 1
Three Mile Island Unit 1 was a pressurized water reactor. It was designed by a company called Babcock & Wilcox. This unit could produce 819 megawatts of electricity.
Building TMI-1 cost about $400 million when it was first built. This would be much more money today. Unit 1 started making electricity on April 19, 1974. It began working fully on September 2, 1974.
TMI-1 used two large cooling towers to cool its main parts. Water from the Susquehanna River was used to replace water that evaporated.
When Unit 2 had its accident in 1979, Unit 1 was not running. It was being refueled. Unit 1 started running again in October 1985. This happened after many discussions and some legal challenges.
Unit 1 was planned to close in September 2019. This was because it was costing Exelon too much money to operate. TMI-1 officially shut down on September 20, 2019.
Three Mile Island Unit 2
The Three Mile Island Unit 2 was also a pressurized water reactor built by Babcock & Wilcox. It was similar to Unit 1 but a bit larger. Unit 2 could produce 906 megawatts of electricity.
Unit 2 received its license to operate on February 8, 1978. It began working fully on December 30, 1978. TMI Unit 2 was permanently shut down after the Three Mile Island accident in 1979.
Unit 2 Generator Use
Even though Unit 2 was shut down, some of its parts were still useful. In 2010, the electrical generator from the damaged Unit 2 reactor was moved. It was taken to the Shearon Harris Nuclear Power Plant in North Carolina.
The generator was very heavy, weighing 670 tons in total. It was repaired and put into use at the Shearon Harris plant in November 2010.
Why the Plant Closed
On June 20, 2017, Exelon Generation announced its plan to close Unit 1. They told the Nuclear Regulatory Commission that they would shut down the plant on September 30, 2019. This was unless the state government helped the nuclear industry.
Bryan Hanson, a senior leader at Exelon, said that once Three Mile Island closed, it could not be reopened. He clearly stated that Unit 1 was closing because it was not making money. Unit 1 had lost over $300 million for the company in the five years before it closed. This was true even though it was one of Exelon's best-performing plants.
When a nuclear plant closes, it needs to be "decommissioned." This means taking it apart safely. There are two main ways to do this:
- Quick Dismantling: The plant is taken apart soon after the nuclear fuel is removed. This can take about 8 to 10 years.
- Long-Term Storage: The plant is put into "mothball" storage for up to 60 years. This allows the radiation to naturally decrease to a safe level. After this time, the buildings are then taken apart. This way, there is less radiation when the work begins. However, the company would have to pay for maintenance and security for many years.
All the used nuclear fuel will be moved to a special storage area in Londonderry Township. This process could also take many years to finish.
In April 2019, Exelon said it would cost about $1.2 billion over almost 60 years to fully decommission Unit 1. Unit 1 closed on September 20, 2019.
Earthquake Risk
The Nuclear Regulatory Commission (NRC) studies the risks to nuclear power plants. In August 2010, the NRC estimated the chance of an earthquake strong enough to damage the reactor core at Three Mile Island. They said it was about 1 in 25,000 each year. This means it was very unlikely to happen.
Images for kids
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The Three Mile Island NPP on Three Mile Island, circa 1979
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September 2019 photo of Three Mile Island and Goldsboro, PA
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A rare image of both units one and two in operation for the few months that they were. It is estimated that this photo was taken in February 1979.
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Unit 2 during its time in operation, viewed from the west
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Aerial view
See also
In Spanish: Planta de energía nuclear Three Mile Island para niños
