Flood Berm Collapses at Nebraska’s Fort Calhoun Nuclear Power Plant

Flood Berm Collapses at Nebraska’s Other Nuclear Station Fort Calhoun

NRC chair tours Cooper plant

June 26, 2011

Associated Press - A berm holding the flooded Missouri River back from a Nebraska nuclear power station collapsed early Sunday, but federal regulators said they were monitoring the situation and there was no danger.

The Fort Calhoun Nuclear Station shut down in early April for refueling, and there is no water inside the plant, the U.S. Nuclear Regulatory Commission said. Also, the river is not expected to rise higher than the level the plant was designed to handle. NRC spokesman Victor Dricks said the plant remains safe.

The federal commission had inspectors at the plant 20 miles north of Omaha when the 2,000-foot berm collapsed about 1:30 a.m. Sunday. Water surrounded the auxiliary and containment buildings at the plant, it said in a statement.

The Omaha Public Power District has said the complex will not be reactivated until the flooding subsides. Its spokesman, Jeff Hanson, said the berm wasn’t critical to protecting the plant but a crew will look at whether it can be patched.

“That was an additional layer of protection we put in,” Hanson said.

The berm’s collapse didn’t affect the reactor shutdown cooling or the spent fuel pool cooling, but the power supply was cut after water surrounded the main electrical transformers, the NRC said. Emergency generators powered the plant until an off-site power supply was connected Sunday afternoon, according to OPPD.

NRC Chairman Gregory Jaczko said the loss of the berm at Fort Calhoun nuclear plant doesn’t threaten the safety of the plant.

“There are other structures and systems in place that can ensure they will continue operating safely,” Jaczko said.

Jaczko will tour the Fort Calhoun plant today. His visit was scheduled last week. On Sunday, he toured Nebraska’s other nuclear power plant, which sits along the Missouri River near Brownville. Cooper nuclear power plant is about 75 miles south of Omaha and run by the Nebraska Public Power District.

Jaczko said he can’t predict what the river will do this summer but that NPPD and OPPD seem to be taking appropriate steps to defend against flooding.

Jaczko spent much of his tour of Cooper asking NPPD officials and the NRC’s local inspectors questions about the plant and this year’s flooding. He said his visit was designed to gather information.

NPPD officials have been monitoring river levels closely during the flooding, and they have already brought in more than 5,000 tons of sand to build barricades protecting the Cooper plant, the onsite power substations and the plant’s access roads.

Accessing critical parts of the plant requires visitors to use ladders or steel stairs to climb over sandbag barriers both outside and inside the doors. When Jaczko saw one of Cooper’s two back-up diesel generators, he had to climb over three different sandbag barriers to get there.

The Cooper plant remains dry because it sits at an elevation above the river level. The base of Cooper and its storage area for used nuclear fuel is 903 feet above sea level while on Sunday the river was just above 899 feet.

Cooper would be shut down if the river rose to 902 feet above sea level, but officials say that is unlikely.

“This plant is designed to deal with a flood much higher than we are seeing — 906 feet,” Jaczko said.

Both nuclear plants issued flooding alerts earlier this month, although they were routine as the river’s rise has been expected. Cooper has been operating at full capacity.

Flooding remains a concern all along the Missouri because of massive amounts of water the U.S. Army Corps of Engineers has released from upstream reservoirs. The river is expected to rise as much as 5 to 7 feet above flood stage in much of Nebraska and Iowa and as much as 10 feet over flood stage in parts of Missouri.

The corps expects the river to remain high at least into August because of heavy spring rains in the upper Plains and substantial Rocky Mountain snowpack melting into the river basin.

Q&A with NPPD, OPPD

June 23, 2011

The Columbus Telegram - In an effort to address rumors and public concern, the Journal Star submitted this list of questions to OPPD and NPPD:

Q: People see photos of Fort Calhoun Nuclear Station surrounded by water and dikes near Cooper Nuclear Station being overtopped near Brownville. Are these plants at risk from the Missouri River floods?

OPPD: If you look closely in the photos, our plant, our substation and other buildings are dry behind berms, sandbag walls and AquaDams. The plant is secure from water to the 1,014 feet above sea level elevation (the river is now at 1,006). It also has diesel generators and additional fuel staged to provide power from on site.

NPPD: There have been at least five situations of flooding around the Brownville area since 1952, and Cooper Nuclear Station, which has experienced several floods since it began commercial operation in 1974, was built to withstand various natural disasters, including tornadoes and earthquakes. The site was elevated 13 feet above the natural grade to 903 feet sea level elevation to accommodate the maximum, probable flooding event. (Earlier this week floodwaters came within 18 inches of 902 feet - the mark at which Cooper would be shut down.)

Q: What steps have you taken to protect the power plants?

OPPD: In addition to the sandbagging, the berms and the AquaDams, more power lines were run to the training center and administration building. Concrete barriers were moved into place in some locations.

NPPD: Cooper initiated its flood procedure plan May 30. Plant staff have been filling sandbags and constructing physical barriers to protect the site's equipment in and outside of buildings, substations and electrical switch yards. Also, operations and security staff essential for 24-hour coverage are staying on site.

Q: Comparisons have been made between what happened to Japanese nuclear power plants and those in Nebraska because of their proximity to the Missouri River. Some people say Cooper Nuclear Station is particularly vulnerable because it has the same basic design as the Japanese reactors. (Note: This question does not apply to OPPD because its reactor is of a different design.)

NPPD: Extremely unlikely. The Midwest is not susceptible to a tsunami. ... Cooper is designed against flooding from the Missouri River, and NPPD is confident the safety systems are in place to respond to a major, natural disaster or crisis event. The accident at Fukushima Daiichi was initiated by two severe natural disasters ... an earthquake measuring 9.0 on the Richter scale (and) ... a tsunami.

It is true that both Cooper and the Fukushima Daiichi units are boiling-water reactors. However, it is misleading to make a direct comparison. The plant's General Electric BWR-4 design has been enhanced or modified to include steam-driven coolant pumps that operate independently from AC power. Station batteries are used for automatic operation, and procedures are in place to manually operate without DC power.

Cooper Nuclear Station also houses two permanent redundant safety-related automatic emergency diesel generators capable of powering all safety-related equipment. These diesel units would be the first to go online during an emergency loss of power. They would automatically start and load without operator action. Only one is needed, so the second is additional protection. We also installed a third emergency diesel generator during this past spring's refueling outage.

Cooper has enough fuel to run one diesel generator at least 40 days. A reserve fuel oil supply resides in underground bunkers to protect it from environmental conditions. These bunkers are anchored so as not to "float" if the river table were to rise. The bunkers collectively contain a minimum of 49,500 gallons. Cooper also has two fuel tankers on site, each of which holds 7,000 gallons.

Other equipment, such as fuel pool cooling pumps, four independent sets of batteries that provide DC power to safety-related equipment, a portable diesel generator to charge these batteries and a diesel-driven, portable fire pump, are also on site to provide additional generation and support.

Finally, Cooper has a "beyond-design-basis" strategy to mitigate against events like those that took place in Japan. To our knowledge, the Japanese do not plan for "beyond-the-design" basis.

Q: What happens if the Missouri River floods the reactor building?

OPPD: Fort Calhoun Station is protected to the 1,014-foot line, far above the current sea level elevation. With the containment building sealed, river water cannot enter it. ... The fuel in the spent fuel pool is underwater for a purpose, to stay cool. The top of the spent-fuel pool is at elevation 1,038 feet. The fuel in the containment building also is underwater by design.

NPPD: It is unlikely the Missouri River water will reach the reactor building. Our operational procedures and "beyond-the-design" strategies serve as protection, but we also have physically protected the reactor building from water. Four-foot-high barricades are in place both outside and inside the building. ... The water would have to be above 907 feet sea level elevation before it would intrude the building. That is an approximate 7-foot rise to the river's current water level. Even if water did intrude the building, it would be directed to floor drains.

Q: What is the likelihood that radioactive particles could enter the water or atmosphere from an accident caused by floodwaters?

OPPD: The fuel is safe and secure.

OPPD has made significant upgrades in flood preparation since NRC inspectors found fault with plans for Fort Calhoun last year.

"Because of the NRC findings last year, Fort Calhoun is better prepared to deal with the situation they are in now," Lochbaum said.

The fact that Fort Calhoun has been shut down since April also is helpful, he said, because less heat has been produced by the reactor core.

So if floodwaters were to interrupt the plant's cooling system, workers would have more time to restore cooling, Lochbaum said.

At the Fukushima nuclear complex in Japan, workers had about an hour before the tsunami hit. In this case, OPPD and NPPD had days and weeks to prepare, he said.

Lochbaum's biggest concern is a break in one of the six major Missouri River dams. The U.S. Army Corps of Engineers has made assurances the dams are safe.

"It depends on how far (the water has to travel) and how much water," Lochbaum said.

NPPD: Again, extremely unlikely. Cooper has physical and equipment barriers in place that would prevent any radioactivity from entering the water, the first of which is preventing the water from entering the building.

Q: If floodwaters do inundate Fort Calhoun, what is the risk to people living in the surrounding area?

OPPD: We feel that the plant is secure. The risk to the surrounding area will be provided by the flood, not our plant.

NPPD: We are taking the proactive and precautionary steps to minimize any risk.

Q: Have OPPD and NPPD received phone calls and emails from people concerned about the safety of both plants? What is your response?

OPPD: We have responded with facts on what we are doing to stay on top of the situation. We held a news conference last Friday to address concerns and questions from the news media.

NPPD: We have received a handful of emails. ... Nuclear power is a safe technology. Federal regulations, the industry's nuclear safety culture and history reinforce this. We have repeatedly withstood adverse conditions.

Q: What is the risk if both plants are shut down for months?

OPPD: Obviously, there is a financial impact, depending upon the price of replacement power and the amount needed. OPPD has other generating stations that are still providing power.

NPPD: There may be financial risks whenever a power plant is taken offline for a significant period of time, but NPPD has other generation resources it can call upon. ... It can also buy power on the market from other utilities.