The Nuclear Regulatory Commission said Wednesday that a special inspection team has been sent to the Braidwood Nuclear Power Plant to review the circumstances surrounding dual reactor shutdowns that occurred on Aug. 16.
The reactors at the Exelon Generating Company LLC-owned plant have remained shut down since the incidents occurred at the plant, which is located in Braceville, Ill., 20 miles southwest of Joliet.
“The purpose of the special inspection is to better understand the sequence of both reactor events and the apparent unexpected system interactions,” NRC Region III Administrator Mark Satorius said in a statement.
The NRC said the four-member team will evaluate the events and circumstances surrounding the shutdowns. An initial evaluation, begun the day of the shut downs, has revealed that Unit 2 shut down due to a main generator fault, according to the NRC. One of the valves that controls water flow to a steam generator became stuck open, according to the NRC, and prevented the operator from using the valve to control water flow. About 13 minutes later, Unit 1 also shut down, due to a loss of a secondary cooling system which helps cool a primary water system in the plant. This created a steam release and a loud noise which could be heard by residents living near the plant, the NRC said in a release. The steam contained low levels of tritium – a radioactive isotope of hydrogen – which they said appear to be lower than the regulatory limits for the public.
The NRC said the special inspection team will review the chronology, causes and circumstances surrounding the shutdowns, and the utility’s calculations of how much tritium was contained in the steam that was released. The inspection report documenting the team’s findings will be publicly available within 45 days after the completion of the inspection, according to the NRC.
Exelon said station workers are in the process of making repairs to replace equipment and safely bring both units back online. Workers will be replacing a small, cosmetic piece of metal siding used to cover an outside walkway on the Unit 1 containment building that was affected by the steam release, the company said.
