June 30, 2014
This Month, Hinman Remembers: Fort Calhoun Nuclear Power Plant Flooding
by Eve Hinman
In the spring, it was common that the mighty Missouri River floods as a result of intense seasonal rains and snow melting from the Rocky Mountains- causing the water to swell into the flood plains. After a particularly devastating flood in 1881, a series of six dams and numerous levees were constructed by the U.S. Army Corps of Engineers to tame the river. These controls supported increased farming and development in the surrounding areas. In the 1970s, two nuclear power plants were built along the river in Nebraska, just south of the dams, to serve the growing population. The Cooper Nuclear Power Plant, is just 19 miles from the city of Omaha and provides 25% of the power in Nebraska, while the smaller facility, Fort Calhoun Nuclear Power Plant sits upstream of the Cooper. In 1993 the spring flood broke through a number of dikes and levees around the Cooper plant, which caused a flood in the reactor building- disabling back up power systems and damaging equipment. There was also standing water in areas known to be radioactive. As a result of the investigations performed in the aftermath by the Nuclear Regulatory Commission, over 100 violations were identified and it took about a year for Cooper to reopen.
At the change of the millennium, the Corps of Engineers developed a new philosophy to mimic nature by releasing a burst of water from the dams in the spring, instead of controlling the river flow. This was done to protect the natural wildlife. As nature would have it, a decade-long drought occurred and the bursts of water released by the Corps in the spring did not cause unnecessary flooding.
In June 2011, the drought ended. Excessive snow and rain caused the Corps to release significantly more than their planned bursts of water due to fears of overtopping. The resulting flood caused extensive damages along the river. The Cooper Nuclear Power Plant was prepared after the 1993 flooding and performed well. Fort Calhoun Nuclear Power Plant, which was closer to the water burst released by Gavins Point Dam, however, did flood. The plant was previously shut down for refueling but a fire caused a power outage. The stored fuel could not be cooled for 90 minutes, which put the plant at risk of meltdown. Calhoun houses 600,000 to 800,000 pounds of high level nuclear waste in temporary, on-site storage. Concerns were heightened due to the Fukushima disaster less than six months prior to this event. As a result the Calhoun plant was shut down for 3 years so that adequate mitigation measures could be put into place. The total losses from the flood are estimated to be $2 billion.
There are a number of interesting observations related to this story which are recurrent themes in recent disasters:
- Increased populations close to major rivers or coasts are increasing the cost of disasters.
- Better coordination events amongst the various public entities using or controlling resources is needed (e.g. USACE and NRC).
- Disasters happen. We need to anticipate and prepare for them.
The good news is that all nuclear power plants are being reevaluated for both seismic and flood risks, which will better prepare us for future events.