LISLES, Ill. — The U.S. Nuclear Regulatory Commission has started a Special Inspection to review the circumstances around the loss of off-site power to both La Salle Units 1 and 2 on April 17.
The two Mark II boiling water reactors are operated by Exelon Generation Co., and are located in Marseilles, Ill., roughly 11 miles southeast of Ottawa.
The issue involved a lightning strike that resulted in the loss of external power to Unit 1 and 2. Both units automatically shut down and all control rods were inserted. The emergency diesel generators started and powered the safety-related systems as planned.
Both the Region III staff and the resident inspectors at the plant closely followed the event.
“There was no threat to the safety of the reactors associated with this event, but having two units shut down after an event is not typical and raises questions,” said NRC Region III Administrator Charles Casto. “Our inspectors will look closely at the event and help us get a better picture of what happened and why.”
On Monday, a three-member inspection team began work and will look into the circumstances surrounding the loss of external power. The team’s actions will include gathering information to establish a timeline of events, reviewing the cause of the event, and evaluating the utility’s actions during and after the incident.
The team will also assess equipment performance, a drywell pressure signal, and review the plant’s radiological monitoring throughout the event.
The NRC will issue a report on the Special Inspection within 45 days of its completion.