Commonwealth Edison officials were still searching Sunday for the cause of a fire Saturday at the Zion nuclear power plant that forced the utility to shut down one of its two reactors.
The fire, which began shortly before noon, was in a building away from the twin reactors and involved machinery that converts steam from the reactors into electricity, said Edison spokesman Art Massa. Because of damage to electrical components, the Unit 1 reactor was shut down, he said. But neither workers nor the public were ever at risk, he said.
Utility officials know a hydrogen leak started the blaze, but said it wasn’t in a bus duct, a ceramic connector that links the generator to the distribution system, as originally believed, Massa said. A fire in that area would have been more serious in terms of interrupting use of the reactor, officials said.
The reactor will remain shut down until the cause is determined and repairs made, Massa said. Customers will continue to be served by the plant’s second reactor, and there was no loss of service as a result of the fire, he said.
Workers first spotted smoke on the turbine floor, and went one floor lower and discovered flames, Massa said.
The fire comes on the heels of a $12,500 fine levied against Edison last week for incidents last March 19 at the Zion plant.
The Nuclear Regulatory Commission fined the utility because of problems that included capping the wrong pipes and disabling four safety “sensor” lines during the five-month refueling of the shut-down Unit 1 reactor.
On April 3, the Zion plant was shut down after a fire near an electrical generator. That fire occurred as Edison was bringing one of its reactors back into service after that refueling shutdown.
Its second reactor was scheduled to start up less than a week later, but that procedure was delayed because of the fire.
The plant has had a checkered history and was on the NRC’s “watch list” from 1991 to 1993. Plants on the list are not considered unsafe but have management and maintenance deficiencies that need attention.
Edison spent about $25 million on upgrades to bring the 1974 plant up to standards.
