Federal regulations, specifically 10 CFR 50.72 require that plant owners promptly notify the NRC about emergencies or safety problems. Depending on the nature and severity, these conditions must be reported to the NRC within one, four, or eight hours. The NRC staffs its Incident Response Center 24 hours a day, 365 days a year so as to receive these reports and initiate response by the federal government when appropriate.
Every work day morning, the NRC posts the event notifications received since the last posting on its website. The event notifications also describe reports from other NRC licensees, such as those using nuclear materials for medical and construction applications.
Event notifications dating back to 1999 are archived on the NRC’s website. The “Search Event Reports” can be used to find event reports on a specified plant or involving a specified system. I have not had much luck using this search tool, but it sometimes returns useful information.
The NRC published NUREG-1022 as a guide to plant owners on the agency’s expectations for what should be reported when.
Let’s examine a typical Event Notification Report for a reactor.
(Click to enlarge)
The information in the upper left box indicates the event occurred at the Sequoyah nuclear plant in Tennessee, which is in NRC’s Region II. The event affected the Unit 2 reactor. Sequoyah has two units, both 4-loop Westinghouse pressurized water reactors.
NEAT #1 covered the NRC’s annual Information Digest. The online version of Appendix A to the digest is an Excel spreadsheet of the 104 operating reactors in the United States. Column H (Nuclear Steam System Supplier and Design Type) can be sorted or filtered to show the 29 units with 4-loop Westinghouse pressurized water reactors including the two at Sequoyah. Appendix A provides additional information about Sequoyah Unit 2 including that it is owned by the Tennessee Valley Authority (Column F), has an ice condenser containment design (Column G), was licensed by the NRC to operate on September 15, 1981 (Column L), and has a licensed power level of 3,455 megawatts (Column P).
The information in the upper right box indicates that the event occurred at 12:05 pm eastern time on February 24, 2013, and was reported to the NRC at 3:20 pm eastern time that same day.
The information in the middle right box indicates that the event did not result in one of the four NRC emergency classifications (Unusual Event, Alert, Site Area Emergency, and General Emergency) being declared and was reported to the NRC per paragraphs 50.72(b)(2)(iv)(B) and 50.72(b)(3)(iv)(A) of 10 CFR 50.72.
The middle center box restates that the event affected Sequoyah Unit 2. “M/R” under the Scram Code means that the reactor was Manually shut down using control Rod insertion. The reactor was critical at the time (Rx Crit = Y) and was operating at 25 percent of rated power when the event began. The unit was at 0 percent power at the time of the notification to the NRC.
The Event Text section provides a narrative of what happened. The operators manually tripped the reactor from 25 percent power due to an indicated loss of condenser vacuum. This action constituted a Reactor Protection System (RPS) Actuation while the reactor was critical, meeting the reporting threshold of 50.72(b)(2)(iv)(B). The apparent cause was a faulty pressure switch.
The narrative also states that the auxiliary feedwater system actuated as expected following the trip of the main feedwater pumps. This automatic action constituted a Valid Specified System Actuation, meeting the reporting threshold of 50.72(b)(3)(iv)(A).
The narrative states that all safety related equipment functioned as designed following the shutdown of the reactor.
NEAT #3 will cover the NRC’s online Licensee Event Report (LERs) search tool. Plant owners typically follow-up their Event Notifications with fuller reports chronicling what happened and why. The NRC’s LER search tool accesses reports dating back to January 1, 1980, and can be very helpful in providing contextual background for a recent Event Notification.
The UCS Nuclear Energy Activist Toolkit (NEAT) is a series of post intended to help citizens understand nuclear technology and the Nuclear Regulatory Commission’s processes for overseeing nuclear plant safety.