Nebraska Public Power District (NPPD) declared an unusual event at its Cooper Nuclear Station at 9:04 a.m. on Saturday, December 29, 2018. The utility declared the emergency classification when site personnel discovered a hazardous gas environment in the basement of the plant. While investigating the gas, safety and plant personnel detected a fire within a pipe chase.
The station’s fire brigade extinguished the active fire at 9:51 a.m. but additional responders were brought in to monitor the piping, assess any equipment damage, provide engineering support, and maintain a fire watch in the area until there was no longer any potential for a fire to restart.
The fire was declared out as of 3:00 p.m., after completion of overhaul activities and assurance that a re-flash would not occur. NPPD exited the emergency classification level called a “notification of an unusual event” (NOUE) 3:44 p.m. the same day.
At no time did plant conditions threaten public safety. The plant remained stable and operating throughout the event and continues to operate at this time.
An NOUE is defined as unusual events, minor in nature, which have occurred or are in progress which indicate a potential degradation in the level of station safety at the station. If placed on a scale of 1 to 4, with 1 being the least serious level of an emergency and 4 being the most serious level of an emergency, an NOUE would equal a 1.
In situations like this, plant personnel follow an emergency response plan and notify appropriate local, county, state, and federal agencies as part of their processes.
Cooper Nuclear Station is located three miles southeast of Brownville near the Missouri River. It is owned and operated by the Nebraska Public Power District, with headquarters in Columbus.