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Nebraska's Fort Calhoun Withstands Record Flood

Nuclear Energy Insight

Fall 2011—For much of the summer, the Fort Calhoun nuclear energy facility in Nebraska was an island in the middle of a vastly swollen Missouri River. An unexpectedly large spring runoff from the mountains to its north and higher-than-average rainfall during the spring caused extreme flooding in portions of Nebraska and Missouri.

undefinedFort Calhoun remained dry. The highest water in the unprecedented flood was below the level that the Fort Calhoun reactor is designed to withstand.

The U.S. Army Corps of Engineers, which manages a series of dams along the river, and the independent U.S. Nuclear Regulatory Commission acknowledged that there was no threat to the reactor from water rising around Fort Calhoun. Nonetheless, some worried about the safety of the plant. Omaha Public Power District (OPPD), which owns Fort Calhoun, and the NRC knew the facility was never in danger based on daily checks of the plant’s key safety systems.

“The plant did exactly what it was designed to do,” said Jeff Hanson, OPPD’s manager of public information.

The flood was a planned runoff by the Corps of Engineers, which gave advance warning to OPPD. The notice gave the operator time to make the facility even safer. In addition to layers of safety protection at the plant, OPPD installed an aquaberm around the facility—an eight-foot-tall, water-filled barrier that resembles a giant inner tube surrounding the reactor containment structure and auxiliary buildings. This berm further protected the reactor from rising water from the Missouri River.

Working With the NRC
Fort Calhoun illustrates the efforts of nuclear energy facility operators to enhance safety measures.

In 2010, the NRC asked OPPD to review Fort Calhoun’s flood preparations. “The NRC’s question was, ‘You have this plan, but is it going to work?’ We had to go look, then do the things the NRC had suggested,” Hanson said. As a result, OPPD installed more portable pumps, added new metal flood plates around some of its buildings and verified the readiness of other flood protection, including sandbags.

The work was collaborative, with Fort Calhoun devising the plan and undertaking a supplemental inspection to ensure everything worked as it should. In late August, waters around the Fort Calhoun facility receded and the company terminated its declaration of an “unusual event,” the lowest of the NRC’s emergency status levels.

Fort Calhoun was refueling at the time of the flood, so the reactor already was shut down. Operators hope to bring it back on line to begin producing clean, emission-free electricity by the end of the year.

Read more articles in Nuclear Energy Insight and Insight Web Extra.