Valve Issue Causes Shutdown at Monticello Nuclear Generating Plant

Nearly two years after a contaminated water leak, the Monticello Nuclear Generating Plant shut down Thursday, March 20, due to what operators are calling a “control valve issue.”

In a statement released Friday, March 21, Xcel Energy, which has owned an operated the Monticello facility for more than four decades, stated “a problem with a control valved at our Monticello Nuclear Plant led the system to automatically take the reactor offline, safely shutting it down as it is designed to do. Our team is taking the necessary steps to bring the plant back to full operations, which we expect to be complete by the end of the week.”

It has not followed up to state the plant is back online at this time.

The Nuclear Regulatory Commission – the federal body overseeing operations – released this report:

AUTOMATIC REACTOR SCRAM

The following information was provided by the licensee via phone and email:

“At approximately 1136 CDT on March 19, 2025, with Unit 1 in mode 1 at 97 percent power, a reactor water level transient occurred which resulted in an automatic reactor scram on low reactor pressure vessel water level. The scram was uncomplicated with all systems responding as expected. The cause of the event is under investigation. Containment isolation valves actuated and closed on a valid group 2 signal.

“Operations responded and stabilized the plant in mode 3. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves.

“This event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) due to the reactor protection system actuation while critical, and an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A) for the Group 2 isolation signal.

“There was no impact on the health and safety of the public or plant personnel.

“The NRC Resident Inspector has been notified. The state of Minnesota as well as Wright and Sherburne counties will be notified.”

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

At the time of the event, condensate flushing evolutions were ongoing. It should be noted that prior to the reactor scram, a single feedwater pump tripped which would lower reactor water level.”