BRACEVILLE, Ill. (Aug. 17, 2010) - An electrical fault on Unit 2's main generator system was the cause of the first of two reactor shutdowns at the Braidwood Generating Station early Monday morning, plant technicians said late yesterday. Both units remained offline Tuesday morning as experts worked to determine the cause of the second unit shutdown and bring both units back to service.
The steam release from the plant's secondary steam lines ended by 4:25 a.m. Tuesday. Samples analyzed for tritium showed levels that have no radiation dose impact for this kind of release. By way of perspective, a person standing within the visible water vapor for the 26-hour duration of the release would have received no measurable dose of radioactivity. The steam contained no other radionuclides.
Neither the shutdowns nor the subsequent steam release posed a threat to the health or safety of the public or plant workers.
Station workers are in the process of making repairs to replace equipment and safely bring both units back online. Workers will also be replacing a small, cosmetic section of metal siding used to cover an outside walkway on the Unit 1 containment building that was affected by the steam release.
"Our focus remains on returning the units safely back to service, and keeping everyone informed of our progress," Braidwood Station Site Vice President Amir Shahkarami said.
Both units tripped off line early Monday morning. The Unit 2 turbine automatically tripped off line about 2:06 a.m., followed 13 minutes later by a shut down of the Unit 1 reactor.
Tritium is an isotope of hydrogen with a weak level of radioactivity. It is formed naturally in the upper atmosphere, is a component of rain and is found in virtually all of earth's surface water. Tritium is produced in greater concentrations in commercial nuclear reactors and is routinely discharged into the environment under strict regulatory guidelines. Tritium eventually breaks down into helium.
Braidwood Generating Station is approximately 60 miles southwest of Chicago. The station's two nuclear energy units can produce a total of more than 2,300 megawatts net at full power - enough electricity to power more than 2 million homes.