U.S.Nuclear Reactors 21 - Sequoyah, Tennessee
The Sequoyah Nuclear Plant is located just north of Chattanooga, Tennessee on the shore of Chickamauga Lake on the Tennessee River. The facility is owned and operated by the Tennessee Valley Authority. The plant has two one thousand one hundred and thirty megawatt Westinghouse pressurized water reactors with Unit One going into operation in 1981 and Unit Two going into operation in 1982. Both units were licensed for forty years.
The population in the NRC plume exposure pathway zone with a radius of ten miles around the plant contains about one hundred thousand people. The NRC ingestion pathway zone with a radius of fifty miles around the plant contains about one million people. The NRC estimates that there is a high risk of an earthquake that could damage the plant.
In 1981, one of the plant’s reactors had to be shut down because of a leak of radioactive water. In 1984, radioactive coolant water spilled at the plant due to a technical failure. In 1985, after a contractor could not confirm that the plant safety equipment met NRC standards, both reactors were shut down by the operators. After the TVA submitted a restart plan, the NRC questioned why the plan did not address the design problems that had caused shutdowns of reactors and delays in construction at other TVA nuclear plants. There were also issues about the TVA nuclear management staff. As work on the problems proceeded, other problems were found that had to be addressed. By 1987, The NRC was concerned that the work that had been done had not really addressed all the problems that had been identified and sent in a team to inspect the work. Multiple problems were identified in one of the systems under question. In late November of 1987, The NRC told the TVA that it did not have confidence in all the silicon rubber insulation in the electrical cables at the plant. The TVA replaced all of the insulation. Finally in late 1988, Sequoyah Unit 1 and Unit 2 were restarted. It took over three years for the TVA to deal with all the issues raised by the NRC.
In 1993, a pipe broke in Unit Two and it was shut down. Inspections of similar pipes found that five out of eight locations also had cracks like the broken pipe. Unit One was shut down as a precaution. Repairs were made to the pipes but other problems were found as work proceeded. Unit Two was restarted in late 1993 and Unit One was restarted in early 1994. Unit Two was out of service for seven months and Unit One was out of service for thirteen months. While the primary reason for the shutdown and repair work had to do with the pipes problem, other problems that required work were left over from the time of the major shut down five years before.
The NRC worked hard to deal with the issues at Sequoyah but had to deal with managers at the plants who would have restarted those reactors without addressing a lot of serious problems if they had been allowed to. There were design problem, equipment failures, cracks in piping, substandard insulation used for electrical cables and a host of other problems. Although there were some management changes after the major outage in the 80s, it is still possible that some of the same attitudes toward maintenance and repairs prevail at that plant today. What is especially troubling about this story is that the TVA is a corporation that is owned by the United States Government and there was a big lack of cooperation between this corporation and the NRC, another branch of our national government.
