Fort Calhoun defends against flood

27 June 2011

The Fort Calhoun nuclear power plant switched to diesel generators for a time yesterday amid the severe Missouri flooding that looks set to continue for another month. 


Fort Calhoun during 2011 Missouri flooding
Fort Calhoun during the floods
The power plant has been in cold shutdown since 9 April, when it closed for a routine refuelling outage. In the meantime, storms inundated the wider area causing the Missouri river to rise - with this being exacerbated by melting snow as well as emergency releases of water from upstream dams.


It was three weeks ago that the river rose to a point that Omaha Public Power District declared it an 'unusual event' to the US Nuclear Regulatory Commission (NRC) and this status still applies. The river level has now reached 36 feet (10 metres) above normal and surpassed the record set in 1993.


Fort Calhoun was designed for floods up to 1014 feet above sea level, and the current flood stands at 1006 feet. The official flooding alert will remain until waters recede to 1004 feet, but this may not happen for weeks.


Berms and temporary AquaDams have been installed around Fort Calhoun's main plant buildings as well as the electrical switchyard and administration area. These have prevented flooding of up to two feet (60 centimetres) in various important areas of the plant.


However, one part of an AquaDam suffered a puncture on 26 June allowing water to surround some of the plant buildings as well as the main electrical transformers. This prompted plant managers to disconnect from the grid and run plant safety systems from on-site diesel power. This status remained until checks confirmed it was safe to reconnect to the grid.


The NRC has said that normal and additional diesel tanks are full. Contingency measures are in place, such as sandbagging supplies, emergency food, firefighting kit and a spare diesel generator. 


Staff at the Cooper nuclear power plant, also on the Missouri, are taking action against rising river levels but that plant continues to operate at full power while observing the 'unusual event'.
Researched and written
by World Nuclear News