Site Title

Site Tagline

Main Navigation

• Home
• About TMI
  • About Us
  • Leadership Team
  • Spotlight on the TMI Team
  • FAQ
• News & Events
  • Media Contacts
  • News Releases
  • Upcoming Events
  • Community Newsletters
• Downloads & Links
  • Fact Sheets
  • Links
• License Renewal
  • License Renewal
  • Public Support
  • Timeline
• Environment
  • Environmental Stewardship
  • Clean Air Benefits of Nuclear Energy
  • Environmental Monitoring
  • Preservation
  • Scientific Studies
• Safety
  • Safe Operations
  • Security
  • Emergencey Preparedness
  • Plant Upgrades
• Reliability
  • Plant Reliability
  • Plant Operations
  • Steam Generator Replacement
  • Used Fuel Storage
• Community Support
  • Community Outreach
  • Philanthropy
  • Volunteerism
  • Economic Benefits
  • Presentation Requests
• Contact Us

FAQ

At TMI Unit 1, it is our goal to provide you with helpful information about the station. Below is a list of questions and answers that we receive most frequently from community members. If you have a question that is not answered below, please contact us and we would be happy to respond to it.

License Renewal

When did TMI Unit 1 begin operating?

Three Mile Island Unit 1 began commercial service in 1974 and is licensed to operate until 2014, and AmerGen submitted an application to renew its license for another 20 years. Since AmerGen purchased the plant in 1999, more than $100 million has been invested into the plant to upgrade and improve its operations. AmerGen will invest an additional $350 million into replacing the plant's two steam generators and control rod drive system that are to be completed by the Spring of 2009. Click here for more.

Why is the plant renewing its operating license?

TMI Unit 1's license expires in 2014. The plant is seeking license renewal because it is a valuable component of Pennsylvania's electricity supply. TMI Unit 1 continues to operate at the high standards set by the Nuclear Regulatory Commission (NRC) and the State of Pennsylvania.

The original 40-year operating term reflects the accounting amortization period generally used by electric utility companies for large capital investments such as TMI Unit 1. The term was not based on safety, technical or environmental issues. Click here for more.

What are the steps in the license renewal process?

First, the plant must submit an application to the NRC for renewal, which TMI Unit 1 submitted in January 2008. The application includes general, environmental and technical information in compliance with federal regulations. After the application is submitted, the public may submit a request for a hearing.

The NRC staff reviews the application on two parallel tracks a safety review and an environmental review. In the safety review process, there are a number of steps including a thorough review of the application's safety sections, an informal public meeting, an audit and inspections of the plant's aging management programs. For the environmental review, a public meeting is held, site audits are conducted, and an environmental impact statement is prepared, commented on by the public, and revised with the public's comments. Click here for more.

Environmental

How does TMI Unit 1 help air quality?

TMI Unit 1 has a positive impact on the air quality of Dauphin County and the Commonwealth of Pennsylvania. Each year the plant operates, TMI Unit 1 avoids 271 metric tons of carbon dioxide per hour that would be produced in Dauphin County by a replacement coal power plant. If a coal plant replaced TMI Unit 1, the replacement plant would produce carbon emissions including nitrogen oxide and carbon dioxide equivalent to two million cars. Click here for more.

How is TMI Unit 1 involved in the environmental community?

TMI Unit 1 is a committed environmental steward and takes every precaution to ensure all environmental regulations are met. TMI Unit 1's environmental management system, which is a tool to achieve environmental excellence, is certified under the strict criteria of the International Organization for Standardization (ISO). This certification requires a commitment to compliance with legal and other requirements, to prevent pollution and to ensure continuous improvement in those areas.

TMI Unit 1 annually performs around 1,700 analyses on roughly 1,300 environmental samples taken from the air, water, fish, cow's milk, soil, and food products from around the plant. The analyses regularly provide data that determines that the operation of Three Mile Island has no adverse radiological impact on the environment. Click here for more.

How does TMI protect the natural habitat of the island?

The natural habitat of Three Mile Island was preserved when the reactors were built at Three Mile Island. Wildlife, including deer and birds, live on the island and their habitats have been preserved during the operation of the TMI Units. Click here for more.

Were there any negative health effects from the TMI Unit 2 accident in 1979?

More than a dozen major, independent studies have assessed the possible health effects of the TMI Unit 2 accident. The studies have found no cancer link to TMI. Click here for more.

What is the current status of TMI Unit 2?

FirstEnergy Corp. owns TMI Unit 2. The unit is in a post-defueling monitored storage mode. TMI Unit 2 will remain in this mode until TMI Unit 1 permanently ceases operation. At that time, decommissioning will be scheduled.

Safety

What steps do you take to ensure TMI Unit 1 is running safely?

Protecting the health and safety of the residents of central Pennsylvania is our number one goal. Each day, safety is the top priority of all employees and dictates how every job or task is completed. AmerGen has invested more than $100 million into upgrading equipment since it purchased the plant in 1999. Some of the upgrades include turbine rotor replacements, reactor vessel head replacement, main transformer replacement and auxiliary transformer replacement. TMI Unit 1 is in the process of replacing its two steam generators, which is a $280 million investment in TMIs future.

Three Mile Island Unit 1 has set four separate world records for continuous days of operation of a Pressurized Water Reactor an indicator of a safe, well run plant. Click here for more.

How is the plant's security protected?

Nuclear plants are the most secure commercial facilities in the country. Three Mile Island has met or exceeded all security measures mandated by the Nuclear Regulatory Commission (NRC). The paramilitary forces guarding the plant are among the best-trained private security forces in the nation. Guards participate in extensive training programs and force-on-force drills to prepare them to respond to various scenarios and demonstrate coordination among state and local law enforcement agencies. Click here for more.

Plant Operations

How does TMI Unit 1 work?

There are two types of commercial nuclear energy plants in the United States, the boiling water reactor and the pressurized water reactor. Both plants operate on the same principles and are cooled by ordinary water. The coolant, which is water, is the main link in the process that converts fission energy to electrical energy.

TMI Unit 1 is a pressurized water reactor. Pressurized water reactors heat the water surrounding the nuclear fuel, but safely keep the water under pressure to prevent it from boiling. The hot water is pumped from the reactor vessel to a steam generator. There, the heat from the water is transferred to a second, separate supply of water. This water supply boils to make steam. The steam spins the turbine, which drives the electric generator to produce electricity. Water from the reactor and the water that is turned into steam are in separate pipes and never mix. Click here for more.

What is uranium used for?

While some power plants burn oil, coal, or natural gas to produce electricity, nuclear power relies on small, half-inch long, uranium pellets. Each pellet is capable of releasing as much energy as one ton of coal. Also, a single ton of uranium is as powerful as about 400,000 barrels of oil. But unlike fossil fuels, nuclear power releases no combustion products to the environment. It is clean energy.

The heat generated by nuclear power results from a process called fission, which is the splitting of atoms by even tinier particles, called neutrons. Fission takes place within the nuclear reactor vessel.

These reactor vessels contain the uranium pellets, stacked end-to-end in fuel rods. The fuel rods are arranged in bundles called fuel assemblies. These fuel assemblies make up the reactor core.

The faster the atoms split, the more heat is produced. The rate at which the atoms are split is controlled by special rods, which absorb neutrons. These control rods fit into spaces between selected fuel rods. As the rods are raised, more heat is produced. As they are lowered, fission slows. When the control rods are fully lowered, fission stops.

At this point, water takes over. The nuclear fuel heats the water but the water is kept under pressure to prevent it from boiling. The hot water is pumped from the reactor vessel to a steam generator. There, the heat from the water is transferred to a second, separate supply of water. This water supply boils to make steam. The steam spins the turbine, which drives the electric generator to produce electricity. Water from the reactor and the water that is turned into steam are in separate pipes and never mix. Click here for more.

How is the uranium and radioactive material stored?

TMI Unit 1 and other nuclear plants in the U.S. were designed and built with redundant and multiple barriers to prevent the release of radioactive material into the environment.

The first barrier is the fuel itself: the solid ceramic uranium pellets. During the process of fission, the uranium atoms that make up the pellets split, which creates the heat essential to turn water into steam that turns the blades of the turbine-generator. Fission creates radioactive by-products that remain locked safely inside the ceramic pellets.

The pellets are sealed in metal fuel rods that are approximately 13 feet high and half an inch in diameter. Fuel rods are made of zirconium, which resists heat, radiation and corrosion. The rods are bundled together into fuel assemblies. The fuel assemblies make up the nuclear reactor core, which is about 12 feet in diameter. The reactor core is inside the reactor vessel, which has steel walls 8 inches thick. The reactor vessel sits inside a shield wall, which made of steel-reinforced concrete and is about 5 feet thick. All of this is inside the Reactor Building.

TMI Unit 1's Reactor Building is also steel-reinforced concrete, about 4 feet thick. The Reactor Building wall also includes a steel liner. This structure is designed to contain radiation that could escape from the reactor vessel in the unlikely event of a major accident that involves fuel damage.

These redundant and robust barriers are in place to prevent radioactive material from escaping. Click here for more.

Used Fuel

What happens to the plant's used fuel?

Used fuel, sometimes called spent fuel, from nuclear power plants is safely stored under at least 20 ft. of water, which is a strong radiation shield. There are numerous redundancies to ensure used fuel's safekeeping. The radioactive material is contained in ceramic fuel pellets, which have a melting point of 5,000 degrees and are inside metal rods, which have a melting point of 3,000 degrees. These fuel rods are placed in steel lined, concrete vaults filled with water, where they can be safely stored. The used nuclear fuel decays over time and is less radioactive than the fuel in the reactor. Click here for more.

Is used fuel from other plants stored at Three Mile Island?

No, the storage area was designed for Three Mile Island used fuel only and therefore, only contains Three Mile Island used fuel. Additionally, NRC regulations prohibit any other generating station from storing fuel at the site. Click here for more.