Fort Calhoun NPP containment buildings and electrical transformers surrounded by 70cm of water, as temporary flood berm collapses
The breach in the inflatable berm protecting the Fort Calhoun nuclear power plant occurred at about 1:30 am (1:25am) local time Sunday, the Nuclear Regulatory Commission (NRC) said.
An aerial view of Fort Calhoun Nuclear Power Plant taken on June 16, 2011 showing the extent of flooding at the station. Photo: U.S. Army Corps of Engineer
Reactor shutdown cooling and spent-fuel pool cooling were unaffected, the NRC said.
The plant, operated by the Omaha Public Power District, has been off line since April for refueling.
Emergency diesel generators were activated after the breach, but normal electrical power supply was restored by Sunday afternoon, the agency said.
Containment buildings at the Fort Calhoun plant are watertight, and the reactor cooling system and spent-fuel pool cooling ponds were unaffected, NRC added.
The 2.7m (8 foot) high, 600m long inflatable flood berm surrounding the plant collapsed after being punctured by heavy equipment.
Fort Calhoun, which is about 30 km (19 miles) north of Omaha, was shut down for refueling on April 7 and has not since been restarted. It remains under the Unusual Event declared on June 6.
The 480-megawatt plant which is located north of Omaha shut down about 10 weeks ago to refuel, but has remained shut since due to flooding, according to Omaha Public Power District (OPPD).
The Fort Calhoun NPP has a single CE pressurized water reactor generating about 480 megawatts of electricity, the smallest commercial power reactor in North America.
OPPD is “a customer-owned utility,” which provides electricity to about 346,000 customers in all or parts of 13 counties in east and southeast Nebraska.
Flooding along the Missouri River to continue until mid-August
Water release from the reservoirs and dams along the Missouri River is expected to continue until at least mid-August, resulting “in near-record flooding along portions of the Missouri River.”
The following probability figures are calculated by FIRE-EARTH on April 8, 2011
- Japan (880)³
- United States (865)
- France (855)
- Taiwan (850)
- Belgium, China, Finland, India, South Korea, United Kingdom, Ukraine, Russia, Slovakia, Czech Republic, Armenia, Slovenia, Croatia, Romania, Hungary, Bulgaria, Spain, Pakistan, Argentina, Brazil, Mexico, South Africa, Canada (810)
- Germany, Sweden, Netherlands (800)
- Switzerland (750)
- The list represents a snapshot of events at the time of calculating the probabilities. Any forecast posted here is subject to numerous variable factors.
- Figures in the bracket represent the probability of an incident occurring out of 1,000; the forecast duration is valid for the next 50 months.
- Probability includes a significant worsening of Fukushima nuclear disaster, and future quakes forecast for Japan.
- A nuclear incident is defined as a level 5 (Accident With Wider Consequences), or worse, on the International Nuclear and Radiological Event Scale (INES). See below.
- Safety issues considered in compiling these lists include the age, number of units and capacity of nuclear reactors in each country/state, previous incidents, probability of damage from human-enhanced natural disasters, e.g., earthquakes, tsunamis, volcanic activity, hurricanes, tornadoes, storms, wildfires, flooding… ]
- The Blog’s knowledge concerning the extent to which the factors described in (3) might worsen during the forecast period greatly influences the forecast.
(UPDATED: June 26, 2011)
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