Three Mile Island Unit 2 - A Look Back

The 30th anniversary of the Three Mile Island Unit 2 accident is March 28, 2009. While Exelon Nuclear does not own TMI Unit 2, the company would like to provide information about the accident, how it shaped today's nuclear industry and the current status of TMI Unit 2.

Below, you will find a brief of this information. For additional information, refer to the TMI Unit 2 Backgrounder, TMI Unit 2 Q&A the "Nuclear Energy Then... and Now" document prepared by the Nuclear Energy Institute (NEI) and the TMI Unit 2 Today Fact Sheet.

If you are a member of the media and would like to speak to a representative from Three Mile Island or TMI Unit 2's current owner, First Energy Corp., refer to the media contact list.

The TMI Unit 2 Accident

On March 28, 1979, a combination of equipment failure and the inability of plant operators to understand the reactor's condition culminated in the accident at Three Mile Island Unit 2, near Harrisburg, Pa.

The TMI accident caused no injuries, and at least a dozen epidemiological studies conducted since 1981 have found no discernible direct health effects to the population in the vicinity of the plant.

Industry Changes Increase Safety

Within nine months of the accident, the industry had formed the Institute of Nuclear Power Operations (INPO), with a mission to promote the highest levels of safety and reliability in the operation of nuclear power plants.

INPO developed an assortment of tools to do the job:

  • Performance objectives and criteria for overall nuclear plant operations and for corporate management support of nuclear programs. These documents set the benchmarks for excellence in safety and reliability and are the basis for INPO's onsite evaluations of plant performance and corporate support.
  • Guidelines and "Good Practice" documents that define one method of meeting INPO performance objectives in specific areas. The guidelines establish the basis for sound programs in selected areas of nuclear plant operation. The "Good Practice" documents identify techniques, programs or processes that have been proven particularly effective at one or more nuclear plants.
  • Regular evaluations of nuclear plants and periodic evaluations of corporate support of operating plants. After each evaluation, INPO supplies the utility with a formal report, giving its findings and recommending improvements. Follow-up visits ensure the recommendations are implemented.
  • Special assistance visits at the request of member utilities. These visits, conducted by qualified INPO personnel and industry peers, are designed to help utilities deal with specific technical issues.

INPO also developed several technical programs for gathering and analyzing information on day-to-day plant operations.

In 1985, INPO formed the National Academy for Nuclear Training, which reviews and accredits nuclear utilities' training programs for all key positions at each plant.

TMI Unit 2 Today

TMI Unit 2 has been permanently shut down and is in monitored storage. GPU Nuclear (now owned by First Energy Corp.) placed the unit in monitored storage in December 1993. Monitoring of TMI Unit 2 and its surrounding areas will continue until the unit is fully decommissioned, with regular reports made to the Nuclear Regulatory Commission (NRC), the Commonwealth of Pennsylvania and the public.