Атомная электростанция Форт-Калун: история и текущий статус

The Fort Calhoun Nuclear Generating Station is a shut down nuclear power plant located on between Fort Calhoun, and Blair, Nebraska adjacent to the Missouri River between mile markers 645.6 and 646.0. The utility has an easement for another which is maintained in a natural state. The power plant is owned by the Omaha Public Power District of Omaha, Nebraska. When operational, the plant accounted for 25 percent of OPPD's net generation capabilities. The plant's single Combustion Engineering pressurized water reactor generated 484 megawatts of electricity. This was the smallest rated capacity among all operating commercial power reactors in North America, and as a single unit plant, this also qualified it as the smallest rated capacity nuclear power plant. OPPD's two Nebraska City coal fired plants at 682 (opened 2009) and 649 (opened 1979) MW are both significantly larger. Fort Calhoun houses spent fuel rods in a 40 feet (12 m) 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 storage as well. In total, the Ft. Calhoun reactor has of high level nuclear waste. 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". The plant underwent refurbishment in 2006 by having its steam generators, pressurizer, reactor vessel head, low pressure turbines and main transformer replaced. In 2003, the plant had its operating license renewed for an additional twenty years. With the renewal, the license for Fort Calhoun was extended from August 9, 2013, to August 9, 2033. The 2011 Missouri River floods surrounded the plant with flood water. The nuclear reactor had been shut down and defueled in April 2011 for scheduled refueling. A fire caused electricity to shut off in the spent fuel pools resulting in 90 minutes without cooling qualifying as a "red event", signifying a high level threat to Fort Calhoun operations. The flood and resulting fire was called "one of the most serious safety incidents in recent years" and resulted in a three year cold shut down of the plant. In August 2012 OPPD signed a deal for Exelon Nuclear Partners to manage the plant although OPPD would maintain ownership. In February 2017, OPPD ended the service contract with Exelon by paying a $5 million fee, but will also be subject to "wind down" fees. The plant was shut down on October 24, 2016. In 2010, the population within 10 miles of Fort Calhoun was 20,639; the population within 50 miles was 953,410. The closest major city is Omaha, with a population of 408,958, whose center is 18 mile (29 km) from the plant.

The Nuclear Regulatory Commission's estimate of the risk each year of an earthquake intense enough to cause core damage to the reactor at Fort Calhoun was 1 in 76,923, according to a NRC study published in August 2010.

A flood assessment performed by the Nuclear Regulatory Commission in 2010 indicated that the Fort Calhoun Nuclear Generating Station, "did not have adequate procedures to protect the intake structure and auxiliary building against external flooding events." The assessment also indicated that the facility was not adequately prepared for a "worst case" flooding scenario. A number of potential flood water penetration points were discovered that could have impacted the raw feed water supply to the cooling system, the auxiliary water supply and main switchgear (electrical) room. By early 2011, corrective measures had been implemented.

On June 6, 2011 the Omaha Public Power District, as required by Nuclear Regulatory Commission guidelines, declared a Notification of Unusual Event (minimal level on a 4 level taxonomy) due to flooding of the Missouri River. The Missouri River was above flood stage and expected to rise further, and to remain above flood stage for several weeks to a month. Contractors installed sandbags and earthen berms to protect the facility from flooding. It was reported on June 17, 2011 that the plant was in "safe cold shutdown" mode for refueling and the anticipation of flooding, 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 1008 feet (307 m) above sea level and OPPD officials stated that the current flood protection efforts would protect the plant to feet above sea level. Officials indicated the spent fuel pool is at 1038.5 feet (317 m) above sea level. 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. 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 an hour and a half while the estimated time for the pool to reach boiling temperature was over 88 hours. In response, the Omaha Public Power District declared an alert (second level on a 4 level taxonomy). The evacuation was the first at the facility since 1992, when (ca. 76 t) of coolant leaked into a containment building from the reactor. On June 23 a helicopter contracted by OPPD to survey transmission lines made an unplanned landing south of the plant. Reports described it as an unplanned landing although photographs showed it on its side in a field. Nobody was injured. The Federal Aviation Administration had declared a "temporary flight restriction," in a 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." 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. On June 26, at 1:30 a. m., an 8 feet (2 m) high, 2000 feet (610 m) long water filled rubber "flood berm" that surrounded portions of the plant was punctured by a small earth mover ("Bobcat") and collapsed. The collapse of the flood berm 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. It was reported more than 2 feet (1 m) of water rushed in around buildings and electrical transformers. Backup generators were then used to ensure the facility maintained electrical power for cooling. The rupturing of the flood berm also resulted in approximately 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. 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. On July 11 OPPD installed a new 8 feet (2 m) inflatable berm as a replacement. According to OPPD, the plant is designed to withstand waters up to above mean sea level. The river was not expected to exceed 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. On June 30 one of the pumps used to remove seepage caught fire when a worker was refilling it with gasoline. The worker put the fire out with a fire extinguisher but was burned on his arms and face and he was airlifted via helicopter to Lincoln, Nebraska. OPPD said the fire was in an auxiliary security building area and not in the reactor area and that the plant was never in danger.

Before restarting OPPD spent $180 million recommissioning the plant, and cleared a list of 450 corrective items issued by the NRC. The utility company raised rates twice whilst the plant was down, 5.9 percent in 2012 and 6.9 percent in 2013, citing these costs among other things. The newer problems discovered in 2012 inspection were not included in the calculations. After three years in cold shutdown, the plant regained full power again on December 26, 2013. Two weeks later on January 9, 2014, the plant had to stop producing power again after workers discovered a damaged sluice gate.