Illinois Nuclear Plant Shuts Down Suddenly In Equipment Malfunction

Plant owner just signed a power purchase deal with Walmart

UPDATE, 1:43 p.m. ET: A spokesman for Constellation provided the following statement: “Dresden operators shut down Unit 2 Thursday morning to investigate an instrumentation issue. Technicians will perform appropriate maintenance before returning the unit to service.”

The Nuclear Regulatory Commission posted a report this morning from operators of the Dresden Clean Energy Center nuclear power plant, stating that an “instrumentation failure” while in full operation caused a complete shutdown.

The plant, less than 50 miles from Chicago, shut down at 4:31 a.m. Central Time yesterday, according to the NRC, 

“At 0431 CDT on September 3, 2026, with Unit 2 in mode 1 at 100 percent power, the reactor was manually tripped due to indication of control rod movement and reactor protection system ‘A’ channel half scram, caused by nuclear instrumentation failure.

“The trip was not complex, with all systems responding normally post-trip. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification,” stated the event report, which the NRC posted after it came through from Constellation Energy, which owns the site. A “scram” is a shutdown.

The plant was stabilized during a “hot shutdown,” according to the report. 

Spokesmen for Constellation did not immediately respond to a request for more details. 

The plant is the fourth to have shut down suddenly in the U.S. Fleet since the beginning of August. No plant shutdown has been classified as an emergency, but all were immediate and unplanned. Few details were provided for each.

The U.S. is in the midst of a nuclear power renaissance, driven by a sharp increase in demand for energy—in no small part as a result of the rapid expansion of hyperscale data centers across the country. 

Constellation is now reopening the former Three Mile Island nuclear power plant following the signing of a power purchase agreement with Microsoft. Walmart recently signed a power purchase agreement with Constellation for 176 MW of capacity at the Dresden site, including 30 MW of expanded generating capacity.

In addition to yesterday’s Dresden shutdown, unplanned outages have been reported at the Monticello nuclear power plant in Minnesota, Millstone-2 in Connecticut, and St. Lucie 1 in Florida since the beginning of August. All have returned to power.