Fort Calhoun nuclear power plant - Wikipedia

Fort Calhoun houses spent fuel rods in a 40 foot deep spent fuel pool next to the reactor, and when the pool had nearly reached capacity in 2006, OPPD began to store spent fuel rods above ground in dry cask storageas well. The storage was not designed to house spent fuel permanently, but when plans for Yucca Mountain nuclear waste repository were terminated, OPPD stated that they are "prepared to safely store material on-site as long as necessary".^[2]

Events

See also: 2011 Missouri River Floods

On June 6, 2011 the Omaha Public Power District, as required by Nuclear Regulatory Commission guidelines, declared a Notification of Unusual Event^[11][12] (minimal level on a 4 level taxonomy) due to flooding of the Missouri River.^[13] The Missouri River is above flood stage and is expected to rise further and remain above flood stage for several weeks to a month. Contractors have been busy installing sandbags and earthen berms to protect the facility from flooding.^[13] According to officials, the plant was built to withstand a 500 year flooding event and though by June 14, 2011, much of the facility was surrounded by the swollen Missouri River, Omaha Public Power District officals were confident that enough redundancies were in place to ensure adequate safety.^[14] It was reported on June 17, 2011 that the plant was in "safe cold shutdown" mode and that four weeks worth of additional fuel had been brought in to power backup generators, should they be needed. The Army Corps of Engineers indicated that with average precipitation, the Missouri River would not go above 1,008 feet (307 m) above sea level and OPPD officials stated that the current flood protection efforts would protect the plant to 1,010–1,012 feet (310–308 m) feet above sea level. Officials indicated the spent fuel pool is at 1,038.5 feet (316.5 m) above sea level.^[15]

On June 7, 2011, an electrical component in a switch gear room caused a small fire with Halon extinguisher activation which forced a partial evacuation.^[16] The fire was no longer burning when the on site fire brigade arrived and according to officials, the public was never in any danger. The fire impacted pumping of coolant water through the spent fuel pool. Cooling was interrupted for 90 minutes while the estimated time for the pool to reach boiling temperature was over 88 hours.^[17] In response, the Omaha Public Power District declared an alert^[18][12] (second level on a 4 level taxonomy). The evacuation was the first at the facility since 1992, when 20,000 US gallons (76,000 l; 17,000 imp gal) (ca. 76 t) of coolant leaked into a containment building from the reactor.^[19][20]

On June 23 a helicopter contracted by OPPD to survey transmission lines made an unplanned landing 1.5 miles south of the plant. Reports described it as an unplanned landing although photographs showed it on its side in a field. Nobody was injured.^[21] The Federal Aviation Administration had declared a "temporary flight restriction," in a two nautical mile radius, centered on the Fort Calhoun nuclear facility. This restriction went into effect on June 6, 2011, at 4:31 PM, and remains in effect "until further notice."^[22] Officials noted that the June 6 FAA directive was actually a reminder to a standing order creating no flight zones over all U.S. nuclear power plants which had been in effect after the 2001 9/11 attacks.^[23]

On June 26, at 1:30 a.m., a 8 feet (2.4 m) high, 2,000 feet (610 m) long flood berm surrounding portions of the plant, was punctured by a small earth mover ("Bobcat") and collapsed.^[24] The flood berm was water-filled and its collapse allowed flood waters to surround the auxiliary and containment buildings at the plant, and also forced the temporary transfer of power from the external electricity grid to backup electrical generators.^[4] It was reported more than 2 feet (0.61 m) of water rushed in around buildings and electrical transformers.^[25] Backup generators were then used to ensure the facility maintained electrical power for cooling.^[26] The rupturing of the flood berm also resulted in approximately 100 US gallons (380 l; 83 imp gal) of petroleum being released into the river as many fuel containers were washed out. The fuel/oil containers were staged around the facility to supply fuel for pumps which remove water within the flood containment barriers. ^[27] The rubber berm was a secondary measure not mandated by the NRC and was put in place by OPPD to provide additional room for work immediately outside the reactor buildings.^[4]

According to OPPD, the plant is designed to withstand waters up to 1,014 feet above mean sea level. The river is not expected to exceed 1,008 feet. NRC officials were at the plant at the time and NRC statements said the plant remains safe. NRC Chairman Gregory Jaczko confirmed the plant's safety when he visited the plant on June 27.^[28][29]

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