Large chunk of ice forces Exelon’s Byron 1 nuclear unit offline

Problems with a large piece of unit resulted in the Exelon (NYSE:EXC) Byron 1 nuclear facility in Illinois going offline March 3, according to information filed with the Nuclear Regulatory Commission (NRC).

“The unit went offline Tuesday at 11:01 a.m. CDT. Early indications show likely cause is ice intrusion in one of the unit’s main power transformers,” an Exelon spokesperson told GenerationHub.

“We do not have an estimated restore time,” the Exelon representative added.

Details of the incidents were laid out in an event notification report filed with NRC.

“The trip occurred following a trip of the Byron Unit 1 East Main Power Transformer (MPT). Initial indications appear that the MPT trip was caused by a large (~ 5 foot) section of ice that fell from a bus bar over the 1E MPT,” according to the report. “This ice shorted out a MPT bushing, resulting in the unit trip. Reactor operators performed a manual start of the Auxiliary Feedwater System in response to the unit trip. All other safety systems responded as expected.”

Byron Unit 2, the opposite unit, is operating at 100% power and stable, NRC said. An investigation is in progress to determine the extent of required repairs, if any, required prior to unit restart.

Bryon Units 1 and 2 are both pressurized water reactors (PWRs) with listed nameplate capacity of roughly 1,200 MW.

About Wayne Barber 4201 Articles
Wayne Barber, Chief Analyst for the GenerationHub, has been covering power generation, energy and natural resources issues at national publications for more than 20 years. Prior to joining PennWell he was editor of Generation Markets Week at SNL Financial for nine years. He has also worked as a business journalist at both McGraw-Hill and Financial Times Energy. Wayne also worked as a newspaper reporter for several years. During his career has visited nuclear reactors and coal mines as well as coal and natural gas power plants. Wayne can be reached at