NRC Keeping an Eye on Water Levels along the Mississippi and Missouri Rivers

Victor Dricks
Senior Public Affairs Officer, Region IV

Heavy rains and subsequent flooding across America’s heartland are being carefully watched by the NRC and the operators of nuclear power plants located along the Missouri and Mississippi Rivers, although none of the plants are expected to be adversely affected.

Flooding is one of the many natural hazards that nuclear power plants must be prepared for. As a condition of their operating license, every nuclear power plant must demonstrate the ability to withstand extreme flooding and shut down safely if necessary – requirements that have been updated and strengthened following the Fukushima accident in 2011.

arkansasAccording to the National Weather Service, the threat of significant flooding is expected to persist for another two weeks in parts of Nebraska, Missouri, Arkansas, Mississippi and Louisiana – all states with operating nuclear power plants. Each of these plants has emergency diesel generators that can supply backup power for key safety systems if off-site power is lost. And all plants have robust designs with redundancy in key components housed in buildings with watertight doors.

In Nebraska, water levels are high along the Missouri River in the vicinity of Fort Calhoun and Cooper Nuclear Station, but not high enough to require any mitigating actions by plant operators.

In Missouri, the Callaway plant is not expected to be affected by any of the heavy rains and flooding that have plagued other parts of the state.

Arkansas Nuclear One, in Russellville, has not been affected by heavy rains and no impact is predicted. But some local roads that lead to evacuation routes were flooded, prompting local law enforcement officials to post detour signs.

At Grand Gulf in Mississippi, levels on the Mississippi River continue to rise, with a crest expected on January 15. The projected river levels, however, are not expected to have any effect on site operations.

At River Bend in Louisiana, the situation is similar. There, the Mississippi River level is expected to peak on January 18, at a level that will not affect site operations. Further downstream, levels on the Mississippi River near the Waterford nuclear plant are expected to crest at a level two feet below where the operator would need to take some actions at the site.

Walkdowns (3)Richard Smith, the Acting Chief of Region IV’s Response Coordination Branch, said his staff is getting periodic updates from the National Weather Service on conditions that might affect any of the region’s nuclear plants. Additionally, the NRC is relying on its resident inspectors, who live in the communities near the plants where they work each day, to independently verify that precautionary flooding procedures taken by plant operators are being properly implemented.

“We’re following events closely here in the Region,” Smith said, “and if anything changes significantly our on-site inspectors will be able to confirm that the operators are taking appropriate protective actions.”

 

Looking For Better Ways to Determine Severe Weather Hazards

Thomas Nicholson
Senior Technical Advisor
Office of Nuclear Regulatory Research

 

The NRC staff evaluates flood hazards when we review applications for new nuclear facility sites. In addition, we re-examine flooding at operating nuclear power plants — a result of what we learned from the 2011 tsunami flooding at Fukushima Dai-ichi in Japan. These evaluations cover a range of flood events including extreme storms that produce intense local rainfall. The NRC works with other federal agencies to better understand events caused by severe weather as we develop ways to better evaluate possible flooding issues at these sites.

weatherBefore the Fukushima event, the NRC staff informed the Federal Subcommittee on Hydrology of the urgent need to update the National Weather Service’s reports for estimating extreme rainfall events. We use these reports as the basis for our flood design and protection studies. As a result, the subcommittee formed a task force and later the Extreme Storm Events Work Group. The work group is looking at the best practices being used to study extreme storms, and developing estimation procedures and guidance.

The Extreme Storm Events Work Group has an impressive membership. In addition to the NRC, it includes the National Weather Service, U.S. Army Corps of Engineers, U.S. Bureau of Reclamation, Federal Energy Regulatory Commission, Natural Resources Conservation Service, Tennessee Valley Authority, and the U.S. Geological Survey. The work group meets monthly to talk about ongoing activities and products federal agencies are developing to help monitor, model and publish rainfall estimates.

Based in large part on the group’s work, we held a three-day workshop last year on probabilistic flood hazard assessment. The workshop brought together more than 250 international experts and included presentations and panel discussions on extreme rainfall events, coastal storm surge flooding, river flooding, tidal waves, flood-induced dam and levee failures, and combined flood events.

More recently, the work group held a workshop at the National Weather Service to define needed extreme storm products for the nation. These products will greatly assist the federal agencies that are moving towards a risk-informed approach for assessing flooding hazards. NRC staff members are benefiting greatly by their interactions with their federal counterparts in the work group.

Nuclear power plants are built to withstand local extreme weather, but we are always learning how safety margins can be improved even more. By working with weather experts in other federal agencies, we can build on what they’re doing and our nuclear power plants will benefit from this collaboration. We can’t stop flooding from happening, but we can make sure the facilities we regulate are prepared to deal with it safely.