An advanced auxiliary feed water storage tank, installed after the Fukushima nuclear disaster to resist similar effects, is seen at TVA's Watts Bar nuclear plant Wednesday, April 29, 2015, in Spring City, Tenn. TVA plans for the nuclear plant's second reactor unit to come online by the end of the year.

Federal regulators are backing away from the strictest rules proposed for U.S. nuclear plants to respond to worst-case instances of floods or earthquakes, contending that nuclear plants have already made significant improvements to ensure their safety.

In a rare split vote along partisan lines, the U.S. Nuclear Regulatory Commission voted 3-2 this week to strip proposed safety rules that would have required nuclear plants to take extra measures based on recent science to protect against hazards such as floods and earthquakes. The NRC said it had already tightened its standards for plants to protect equipment reliability from floods or earthquakes like those that created the tsunami and nuclear disaster at the Fukushima Dai-ichi nuclear plant in Japan, which forced more than 160,000 people from their homes in 2011.

The Tennessee Valley Authority was one of the first utilities to implement Diverse and Flexible Coping Strategies – known as FLEX in the nuclear industry – at all three of its nuclear plants to ensure backup diesel generators and other safety equipment were protected in a food or earthquake like those that damaged the Fukushima plant in Japan. TVA spent more than $400 million to install new FLEX buildings and other safety systems at its Watts Bar, Sequoyah and Browns Ferry nuclear plants since 2011 to ensure the equipment and backup power systems for its nuclear plants can still operate in the event of a flood or major earthquake.

The Unit 2 reactor at Watts Bar, where TVA spent nearly $200 million on building and dam upgrades in the wake of the Fukushima disaster, became the first and so far only new nuclear reactor brought on line in the 21st century when the unit became operational in 2015.

"We have FLEX buildings at each of our sites, where we house backup diesel generators, pumps and other equipment that can be used if our multiple off-site power sources are compromised," TVA spokesman Jim Hopson said. "In addition, we have access to portable equipment and resources from the National SAFER Response Centers located in Memphis, Tennessee and Phoenix, Arizona. These centers are capable of delivering complete sets of emergency equipment to help facilities respond safely to extreme events no matter what causes them."

NRC Chairman Kristine Svinicki, a Republican, said the commission's work since 2011 has resulted in "tangible safety improvements at every U.S. nuclear power plant."

But NRC Commissioner Jeff Baran, a Democrat, said NRC staff had included the extra safety measures in the draft after years of work to help protect the public from an incident like Fukushima happening at a U.S. commercial reactor

"Instead of requiring nuclear power plants to be prepared for the actual flooding and earthquake hazards that could occur at their sites, the NRC will allow them to be prepared only for the old out-of-date hazards typically calculated decades ago when the science of seismology and hydrology was far less advanced than it is today," Baran said after the vote.

Stephen Burns, a registered independent whom former President Barack Obama appointed to a Democratic seat on the commission, also voted against the measure.

Svinicki disputed the Democrats safety concerns about flooding and earthquake hazards, arguing that "in the view of the commission majority this is not the case." Regulations already in place already address the issues, she added.

But the Union of Concerned Scientists objected to the NRC backing away from the staff-recommended rules.

"Nearly eight years after the Fukushimi accident, the NRC continues to disregard a critical lesson: Nuclear plants must be protected against the most severe natural disasters they could face today—not those estimated 40 years ago," said Dr. Edwin Lyman, acting director of the Nuclear Safety Project at the Union of Concerned Scientists.

Nuclear plant operators have re-evaluated seismic and flooding hazards in the wake of Fukushima and Lyman said what they found is not reassuring. About two-thirds of U.S nuclear plants face hazards beyond what they were originally designed to handle, including higher flood levels from extreme precipitation, upstream dam failure and storm surge.

The reevaluated flood height for local intense precipitation for the Palisades plant in Michigan, for example, was more than 25 feet higher than the level considered in the plant's original design. Similar concerns were identified in many seismic risk evaluations.

"The NRC must require plant owners to upgrade their facilities based on the best current information, the most realistic analyses, and the potentially devastating impacts of increased flooding from climate change," said Dr. Lyman. "Failing to do so will leave some nuclear plants dangerously unprepared and needlessly invite disaster."

Despite changes in the final rules to be published by the NRC by spring, the regulators said they will require nuclear operators to be able to cool the reactor core and preserve resources needed to protect the reactor core based upon the lessons learned from Fukushima within two years.

"The NRC and its nuclear power plant licensees will continue post-Fukushima efforts outside of the rulemaking context, including analyses of whether additional safety improvements are necessary in response to updated site-specific seismic and flooding risk assessments," NRC spokesman Scott Burnell said Friday.

Contact Dave Flessner at or at 757-6340.