Equipment failure caused Byron event

Plant officials say it was a broken insulator at the facility’s switchyard that caused Monday morning’s “Unusual Event” at the Byron Generating Station.

The incident was reported at around 10 a.m. Monday, and the plant’s Unit 2 generator remains off-line. On Monday morning, Unit 2 automatically tripped off-line due to a loss of off-site power to the unit.

When the loss occurred, the facility’s diesel generators activated to provide back-up power. The steam release that began when Unit 2 came off-line stopped at approximately 3 a.m. on Tuesday.
Byron technical experts have completed repairs to a failed insulator, which was the source of the power loss, states an Exelon news release. A comprehensive investigation into why the insulator failed is ongoing, the release states.

“We will send off for failure analysis to see if we can learn why it failed,” said Paul Dempsey, communications manager for the Byron Generating Station.

Plant officials say there was no health or safety risk to workers or the general public during the incident, since the facility’s back-up systems all functioned correctly. Even so, Exelon Nuclear has notified the appropriate local, state, and federal authorities of the incident.

An Unusual Event is the lowest of the four emergency classifications established by the U.S. Nuclear Regulatory Commission. It is unclear when Unit 2 will be reactivated, but in the meantime, the plant’s Unit 1 generator continues to supply electricity.

On Tuesday, personnel from the Illinois Emergency Management Agency collected samples from around the Byron plant to confirm that the steam release during Monday’s event poses no hazard to the public. The samples will be taken to the agency’s Springfield lab for analysis and results should be available in a few days, states an IEMA news release.

Patti Thompson, a spokesperson for IEMA, said the sampling will allow her agency to determine whether there are any dangerous levels of radioactive tritium present in the environment surrounding the plant. The agency does not expect there to be any elevated levels, but the sampling and testing will confirm this, Thompson said.

“Nothing indicates to us that there should be elevated levels, but we want to do our own independent testing,” Thompson said.

As part of this process, IEMA personnel are collecting water and vegetation samples. Some of the samples will be in the same locations as routine sampling that was conducted by the agency within the past month. Other samples will be taken elsewhere.

Thompson said the new samples will be compared to the samples taken a short time ago, which will make the process easier.

“Hopefully, within the next few days, we’ll have results and we can let the public know,” Thompson said.