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On June 6, 2011, the Fort Calhoun pressurized water nuclear reactor 20 miles north of Omaha, Nebraska entered emergency status due to imminent flooding from the Missouri River. A day later, there was an electrical fire requiring plant evacuation. Then, on June 8th, NRC event reports confirmed the fire resulted in the loss of cooling for the reactor's spent fuel pool.

Electrical Fire Knocks Out Spent Fuel Cooling at Nebraska Nuke Plant
by John Sullivan
Special to ProPublica June 9, 2011, 11:20 a.m.

A fire in an electrical switch room on Tuesday briefly knocked out cooling for a pool holding spent nuclear fuel at the Fort Calhoun nuclear plant outside Omaha, Neb., plant officials said.

The safety of deep pools used to store used radioactive fuel at nuclear plants has been an issue since the accident at Japan's Fukushima nuclear plant in March. If the cooling water a pool is lost, the used nuclear fuel could catch fire and release radiation.

As ProPublica reported earlier, fire safety is a continuing concern at the country's 104 commercial reactors, as is the volume of spent fuel piling up at plants.

Officials at Fort Calhoun said the situation at their plant came nowhere near to Fukushima's. They said it would have taken 88 hours for the heat produced by the fuel to boil away the cooling water.

Workers restored cooling in about 90 minutes, and plant officials said the temperature in the pool only increased by two degrees.

The fire, reported at 9:30 a.m., led to the loss of electrical power for the system that circulates cooling water through the spent fuel pool, according to a report from the Nuclear Regulatory Commission. A chemical fire suppression system discharged, and the plant's fire brigade cleared smoke from the room and reported that the fire was out at 10:20 a.m., the NRC said.

Mike Jones, a spokesman for the plant's owner, the Omaha Public Power District, said Fort Calhoun has a backup pump to provide water to the spent fuel in case the main system is lost. That pump, which runs on a separate power supply from the rest of the plant, was inspected and standing by on Tuesday, but plant operators restored main power to the pool before the emergency pump was needed, he said.

Fort Calhoun's single reactor has been shut down since April for refueling. The plant had already been operating under a heightened level of alert because of nearby flooding on the Missouri River, the NRC said. The cause of the fire remained under investigation this morning.

http://www.theoilage.com/fort-calhoun-n ... t3752.html

http://cryptome.org/eyeball/ne-npp-floo ... -flood.htm
Nebraska, le Missouri des centrales nucléaires des conditions d'inondation du fleuve

La station de Fort Calhoun énergie nucléaire à Fort Calhoun, au Nebraska, actuellement fermée pour le ravitaillement, est entourée par les eaux de crue de la rivière Missouri, mardi, Juin 14, 2011. Le mardi, les rejets au barrage Point Gavins dans le Dakota du Sud a frappé le montant maximum prévu de 150 000 pieds cubes d'eau par seconde, ce qui devrait accroître la rivière Missouri 5-7 pieds au-dessus du niveau d'inondation dans la plupart du Nebraska et en Iowa. AP [La rivière Missouri est en bas à droite.]

Nebraska Nuclear Plant Lost Cooling System After Fire

WASHINGTON—A nuclear power plant north of Omaha, Neb., on Tuesday briefly lost the ability to cool a pool of used nuclear fuel after a fire at the site, the U.S. Nuclear Regulatory Commission said.

The NRC said the plant recovered cooling ability without activating backup systems and "temperatures in the pool remained at safe levels." The public was not in danger because the plant has been shut down since early April for a refueling outage, the agency said.

Spent fuel pools in the U.S. have received increased scrutiny after a recent crisis in Japan involving potentially overheated nuclear fuel and the release of dangerous radiation.

The agency declared an alert, the second of four emergency classes, at 9:40 a.m., 10 minutes after "an indication of fire" in a building at the plant. The NRC didn't disclose the cause of the fire. Automatic fire control systems activated and the fire was out by 10:20 a.m., the agency said. The plant is operated by the Omaha Public Power District.

Nuke plant lost spent fuel pump in suspected fire

ATLANTA (AP) — A nuclear power plant in Nebraska briefly lost the pump used to cool spent nuclear fuel during a suspected electrical fire.

Utility officials said the fire Tuesday damaged an electrical system used to run a pump at the Fort Calhoun Station that recirculates water in a pool holding hot, radioactive nuclear fuel that has been used.

The pump was out of commission for an hour before the system was restored. Omaha Public Power District spokesman Mike Jones said the company had backup equipment but didn't need to use it. Jones initially said that plant operators deliberately took the pump offline to respond to the fire.

If a pool pump fails for several days and is not fixed, cooling water could boil away and eventually cause radioactive releases.

...Workers restored cooling in about 90 minutes, and plant officials said the temperature in the pool only increased by two degrees.

The fire, reported at 9:30 a.m., led to the loss of electrical power for the system that circulates cooling water through the spent fuel pool, according to a report from the Nuclear Regulatory Commission. A chemical fire suppression system discharged, and the plant's fire brigade cleared smoke from the room and reported that the fire was out at 10:20 a.m., the NRC said.
....

No danger seen at reactor

Friday June 17, 2011

Despite the stunning sight of the Fort Calhoun nuclear reactor surrounded by water and the weeks of flooding that lie ahead, the plant is in a safe cold shutdown and can remain so indefinitely, the reactor's owners and federal regulators say.

“We think they've taken adequate steps to protect the plant and to assure continued safety,” Victor Dricks, spokesman for the Nuclear Regulatory Commission, said Thursday.

Tim Burke, vice president at Omaha Public Power District, said the plant's flood barriers are being built to a level that will protect against rain and the release of record amounts of water from upstream dams on the Missouri River.

“We don't see any concerns around the Fort Calhoun Nuclear Station,” Burke said at a briefing in Omaha Mayor Jim Suttle's office.

The nuclear plant, 20 miles north of Omaha, was shut down April 9 for refueling. It has not been restarted because of the imminent flooding.

..........

...Perhaps it's just as well that Fort Calhoun got into trouble last year with federal regulators over flood preparedness. During routine inspections in June 2010, the NRC concluded that deteriorating conditions during catastrophic flooding could make sandbagging near the river difficult.

Regulators required OPPD to improve flood defenses and signaled in April that those improvements were taking the plant in the right direction.

......

Elizabeth Ishan Cory, a spokeswoman for the Federal Aviation Administration, said the flight restrictions at Fort Calhoun are intended to keep curiosity seekers out of the immediate vicinity. Planes can still fly near the plant if they have flight plans and are in contact with air traffic controllers. Smaller aircraft are restricted in how close they can get to the plant.

Otherwise, there's a risk of midair collisions that could jeopardize operations on the ground.

“When you keep the area above the ground safe, you're going to keep the people on the ground safe, too,” Cory said.

......Nuclear expert Arnie Gundersen said that he doesn't expect a melt-down, as the diesel generators are situated higher above the ground than at Fukushima, so - unless the water rises further than expected - they should keep working:

.....

A l’origine des faits, une crue du Missouri

Tout a commencé le 6 juin, quand une alerte est lancée en raison d’une crue imminente du Missouri. En raison de fortes pluies additionnée à la fonte des neiges, le barrage de Point Gavins, situé en amont, a dû relâcher une très importante quantité d’eau. Une vague déferle sur le Missouri et inonde les alentours de la centrale. Le lendemain, un feu se déclare dans la salle des commutateurs. Les fumées toxiques entraînent l’évacuation de la centrale. Heureusement, le système d’extinction automatique vient à bout du feu. Mais des câbles alimentant les pompes du système de refroidissement ont été endommagées. La centrale perd son système de refroidissement pendant plusieurs heures.

Fort Calhoun, une centrale nucléaire déjà pointée du doigt

La centrale de Fort Calhoun est une centrale équipée d’un réacteur à eau pressurisée. Le réacteur a été arrêté au mois d’avril, pour la recharge du combustible. Le combustible usagé est stocké dans une piscine, pour achever son refroidissement (opération qui dure plusieurs mois, voire une année). Elle contient probablement aussi du combustible neuf, en attente de chargement dans le réacteur.
Comment se fait-il que cette centrale, pourtant rénovée en 2006, ait perdu son système de refroidissement suite à une simple inondation ? On imagine les centrales nucléaires équipées de multiples générateurs de secours et prêtes à affronter les risques élémentaires liées à leur position en bord de l’eau. Il semblerait que ce ne soit pas le cas… En 2010, l’Autorité de sureté nucléaire américaine avait publié un rapport indiquant que la centrale de Fort Calhoun n’avait pas de procédures de protection contre les inondations. Un comble !