In recent months, the NRC has identified additional performance and technical issues that will need to be resolved before the Fort Calhoun Nuclear Station can restart. The plant, located about 19 miles north of Omaha, Neb., shut down on April 9 for a refueling outage. The outage was extended due to flooding along the Missouri River. Then an electrical fire on June 7 led to the declaration of an “Alert” and caused further restart complications.
On September 2 the NRC issued a Confirmatory Action Letter documenting actions that Omaha Public Power District (OPPD) officials agreed to take prior to seeking permission from the NRC to restart. The NRC later dispatched a special inspection team to review circumstances surrounding the electrical fire. The fire had resulted in the loss of spent fuel pool cooling capability for a brief time and caused significant unexpected system interactions.
During the fall, OPPD employees have been working their way through an extensive checklist of actions needed to assess damage to the site as well as checking structures, systems and components for damage that may have been caused by flooding.
All of this has been occurring against a very significant backdrop: On Sept. 1, the plant was placed in Column Four of the NRC’s Reactor Oversight Process Action Matrix because of multiple violations of NRC regulations. These include a “yellow” finding of substantial safety significance because of inadequate strategies to protect the plant from flooding and a “white” finding of low to moderate safety significance for the failure of electrical components used to automatically shutdown the reactor. Column Four is reserved for plants with significant performance issues.
The discovery of additional concerns, which are still being studied and evaluated, further complicates matters. The Alert caused by the breaker fire resulted from inadequate design or installation of electrical components. Deficiencies were noted with environmental qualification analyses for plant structures, systems and components. These analyses are relied on to demonstrate that key systems will be able to perform their safety functions under a variety of challenging accident conditions like earthquakes, loss of coolant accidents, high radiation fields, seismic events, etc.
There also are concerns with the plant’s emergency response program. OPPD officials failed to notify state and local officials of the June 7th Alert within the required 15 minutes. In a separate emergency exercise, OPPD withdrew a protective action recommendation after it had been communicated to emergency responders.
For these reasons, NRC senior managers have decided to increase oversight of Fort Calhoun using Inspection Manual Chapter 0350, which is reserved for facilities that are shut down due to significant performance and/or operational concerns. This inspection process provides guidance to the NRC staff to ensure that licensee corrective actions will be sufficient to safely restart and operate the plant.
The 0350 process has only been used for 12 other sites since 1994, making this an infrequent – and important – step to maintaining safety as U.S. nuclear power plants. Stay tuned for more information about this site in the future.