A Nuclear Regulatory Commission spokesman told The Independent Friday that dry cask storage of spent nuclear fuel rods at two Nebraska facilities are not being protected from flood waters because the situation poses no public or environmental threat.

Victor Dricks, an NRC Region 4 spokesman, said by phone Friday afternoon that the regulatory agency continues to closely monitor conditions along the Missouri River where floodwaters are rising at the Cooper and Fort Calhoun nuclear power stations. Flooding, brought on by heavy rainfall and snow melts in northern states, is expected to continue for several weeks.

The Cooper facility, which is owned and operated by Nebraska Public Power District, continues to operate at full power. Fort Calhoun, owned by Omaha Public Power District, was shut down for refueling on April 7. Although workers have finished refueling, the facility will be kept offline until the flood waters recede.

Following an earlier report published by The Iowa Independent about flooding at the nuclear facilities, questions were raised about the placement of dry cask storage of spent nuclear fuel rods with some questioning if the facilities storing these rods were within flood protection barriers.

“They are not within the flood protection barrier,” Dricks said. “There’s no reason for them to be. Those are large, sealed canisters that are bolted down — no risk with the floodwaters.”

Spent fuel rods are first cooled in a spent fuel pool for a year before being placed in dry cask storage. The fuel is surrounded by inert gas inside a large container, typically steel cylinders that are either welded or bolted closed. That container is then surrounded by another protective layer — typically steel or concrete — as a further radiation shield. Additional technical information on the process of dry storage can be found in a December 2010 report by the U.S. Nuclear Waste Technical Review Board (PDF).

Because of their protected state, Dricks said, there is no danger associated with these storage casks being exposed to the ongoing flood.

“As I said, the situation is being monitored very closely by the NRC, and both Cooper and Fort Calhoun are following emergency protocols to keep the facilities and the public safe,” Dricks said, adding that there is no immediate danger of radiation leaks or any other catastrophic issues.

Walkways are necessary for workers to bridge the height of Aqua Dams and access buildings at Fort Calhoun Nuclear Station. (Photo: Walkways are necessary for workers to bridge the height of Aqua Dams and access buildings at Fort Calhoun Nuclear Station. (Photo: Omaha Public Power District

Both of the facilities have made extensive preparations to protect the sites against rising floodwaters. Cooper, located near Brownville, Neb., sits two-and-a-half feet above current river levels. It remains under an Unusual Event (the lowest of four levels of emergency notification) since June 19. NPPD officials have installed barriers to protect buildings and structures from flooding. A berm has been placed around the plant’s electrical switchyard for additional protection. It is not expected that floodwaters near Cooper will impact vital plant equipment.

Fort Calhoun, which has previously been given worrisome ratings by the NRC in relation to flood preparedness, now has a total of five inspectors and a branch chief on site to provide around-the-clock coverage of licensee activities.

Calhoun sits 19 miles north of Omaha, and also remains under an Unusual Event that was declared on June 6. An eight-foot high, 16-foot wide AquaDam has been placed around the facility, which provides protection for up to six feet of flood waters.

Both Cooper and Calhoun workers have stockpiled additional equipment, including diesel fuel to run emergency generators if necessary. Dricks said both plants have enough fuel to power generators for roughly one month. Power is important because fuel rods in the reactor core as well as spent fuel rods in the cooling pool need to be kept cool. If all power was lost, officials estimate that the pools surrounding the rods, which is kept at 80 degrees, would not reach boiling for roughly 88 hours.