on Unit 1 on September 12, 1966 and originally came online on December 20, 1973. Commercial operation began on August 1, 1974. It was licensed to operate through December 20, 2013. Unit 1 was shut down for a year after a fire in 1975 damaged the unit. The unit was subsequently repaired and operated from 1976 through March 3, 1985, when all three Browns Ferry units were shut down for operational and management issues. Starting in 2002, TVA undertook an effort to restore Unit 1 to operational status, spending $1.8 billion USD to do so. The NRC approved the restart of Unit 1 on May 15, 2007 and the reactor was brought up to criticality on May 22. During initial testing after restart, on May 24, 2007, a leaky hydraulic control pipe in the turbine hall burst, spilling about of non-radioactive fluid, and the newly restarted reactor was temporarily powered down. Reactor power-up and tests resumed on May 27 and the unit started supplying power to the electricity supply grid on June 2, 2007, reaching full power on June 8. The Browns Ferry restart was estimated to pay for itself in five years. On May 4, 2006, NRC issued a renewed license, adding twenty years to operate through December 20, 2033. Unit 1 generated 9,801 GWh of electricity in 2017, achieving a capacity factor of 101.62%. Unit 1 fire On March 22, 1975 a fire started when a worker using a candle to search for air leaks accidentally set a temporary cable seal on fire. At Browns Ferry, foamed plastic, covered on both sides with two coats of a flame retardant paint, was used as a firestop. The fire spread from the temporary seal into the foamed plastic, causing significant damage to the reactor control cabling in the station. An NRC bulletin explained the circumstances of the fire. The fire started in the cable spreading room at a cable penetration through the wall between the cable spreading room and the reactor building for Unit 1. A slight differential pressure is maintained (by design) across this wall, with the higher pressure being on the cable spreading room side. The penetration seal originally present had been breached to install additional cables required by a design modification. Site personnel were resealing the penetration after cable installation and were checking the airflow through a temporary seal with a candle flame prior to installing the