Water levels in the Missouri River have risen over the past few weeks due to a combination of heavy rain and melting snow. The U.S. Army Corps of Engineers released still more water from dams to prevent them from overflowing. Breeched levees have resulted in localized flooding at several points.
On June 6, Omaha Public Power District (OPPD) declared a 'notification of unusual event' at its Fort Calhoun nuclear power plant due to the rising level of the Missouri River and some onsite flooding. This is the least serious of four emergency classifications that are standard in the US nuclear industry.
The utility noted projections from the Corps of Engineers that river levels at the plant site just north of Omaha was expected to reach 1,004 feet above mean sea level and to remain above that level for more than a month. The alert is set to remain in effect at Fort Calhoun until OPPD can be sure the level of the river remains below 1,004 feet.
The 500 MW single pressurized water reactor at Fort Calhoun has been in safe shutdown since April 9, when it entered a scheduled refueling outage. On June 16, OPPD's board of directors approved a measure to authorize plant management to buy any material, equipment or services it needed to prevent flooding at Fort Calhoun, without having to go through the usual procurement process.
"In addition to the existing flood-protection at the plant, OPPD employees and contractors have built earth berms (raised barriers) and sandbagged around the switchyards and additional buildings on site,” officials with OPPD said in a statement. “They also are filling water-filled berms around the plant and other major buildings on site, have staged additional diesel fuel inside the Protected Area and are building additional overhead power lines to provide another option for power for the plant's administration building, training centre and one of its warehouses."
The Nebraska Public Power District (NPPD) has also declared a notice of unusual event June 19 at its 830 MW Cooper nuclear power plant, three miles southeast of Brownville, Neb.
The notification was made as part of the safety and emergency preparedness plan that the plant follows when flooding conditions are in effect. The plan’s procedure dictates when the river’s water level reaches 42.5 feet, or greater than 899 feet above sea level, that a notification is declared.
Workers at the Cooper plant filled sandbags, barricades and reinforced the access road. NPPD said that if the level of the river rises to 45.5 feet, or 902 feet above sea level, the single unit boiling water reactor would be shut down as a protective safety measure.
OPPD released videos showing how the utility prepared for the potential floods over a 15-day period. For OPPD's flood preparation video from June 1, click here
For video from June 4, click here
For video from June 8, click here
For video covering June 10-16, click here
Subscribe to Nuclear Power International