The Rising River Puts Flood Preparations to the Test

Flood protection plans that the NRC requires for all nuclear power plants are now being put to the test by historic flooding along the Missouri River in Nebraska. Rising waters are lapping at three sides of the Cooper Nuclear Station in Brownville. Fort Calhoun, located 19 miles north of Omaha, looks like an island in aerial photos.

One question is on everyone’s mind: Will the flood preparations be good enough?

Cooper, which is operating at full power, sits two and a half feet above current river levels. It remains under the Unusual Event declared on June 19. (Unusual Event is the lowest of four emergency categories established by the NRC.)

Nebraska Public Power District officials have installed barriers required to protect buildings and structures from flooding. A three-foot earth and stone berm has been assembled around the plant’s electrical switchyard for additional protection. If all goes well, floodwaters will not impact vital plant equipment.

The NRC has augmented its inspection staff at Fort Calhoun where there is now two feet of water in many areas onsite. In addition to the two resident inspectors, three more inspectors and a branch chief are there to provide around the clock coverage of licensee activities.

The Ft. Calhoun plant remains under the Unusual Event declared on June 6. Omaha Public Power District (OPPD) officials have not restarted the plant, which has been in a refueling outage since early April. This way they can devote their full attention to dealing with the flood rather than adding the distraction of startup, which can take several days of preparation.

The plant has erected an Aquadam around the powerblock – vital areas including the containment and auxiliary buildings. The water-filled berm is eight feet tall and 16 feet wide at the base, and provides protection for up to six feet of water. The dam also protects several pieces of equipment that have been brought onsite, including an additional emergency diesel generator for supplying AC electrical power, water pumps, firefighting equipment and sandbagging supplies.

An earthern berm protects the electrical switchyard and a concrete barrier has been built around electrical transformers to protect them. Satellite phones have been distributed to key workers. Extra food and water has been stockpiled.

Existing diesel fuel tanks have been topped off and two additional fuel tanks have been brought onsite. Special gas-fired pumps are available in the event of station blackout. If there is a complete loss of power on site the pumps can circulate cooling water through the spent fuel pool and reactor core.

The NRC’s inspections in 2009 revealed deficiencies in OPPD’s flood response plan. The NRC increased its oversight of Fort Calhoun while the plant responded, and today the plant is well positioned to ride out the current extreme Missouri River flooding while keeping the public safe.

The NRC’s Region IV in Texas remains a hive of activity with communications ongoing between the technical staff, the resident inspectors at both sites, and licensee officials. Several times each day, managers discuss flood preparations with their licensee counterparts and receive briefings from the resident inspectors. Licensee plans are questioned, critiqued and where necessary augmented with input provided by NRC staff.

It’s all designed to stay one step ahead of the rising floodwaters.

Victor Dricks
Public Affairs