WASHINGTON (Reuters) - Republicans on the U.S. nuclear power regulator approved a stripped down safety rule on Thursday that removes the need for nuclear plants to take extra measures based on recent science to protect against hazards such as floods and earthquakes.

FILE PHOTO: A Reuters reporter measures a radiation level of 9.76 microsieverts per hour in front of Kumamachi Elementary School inside the exclusion zone in Okuma, near Tokyo Electric Power Co's (TEPCO) tsunami-crippled Fukushima Daiichi nuclear power plant, Fukushima Prefecture, Japan, February 13, 2016. REUTERS/Toru Hanai/File Photo

The Nuclear Regulatory Commission, a board with three Republican seats and two Democratic seats, approved the rule on a 3-2 vote along party lines. Dissents are rare on the NRC and the two members who hold Democratic seats strongly disagreed with the approval.

They said the Republican decision could allow plants to avoid protections against risks of natural disasters that have become apparent with science methods that have evolved since most plants were built about 40 years ago.

A draft rule that included the measures was formed following the 2011 nuclear disaster at Japan’s Fukushima Daiichi plant that was damaged by an earthquake and tsunami, forcing more than 160,000 people from their homes. The draft was presented to the commission in 2016.

Commissioner Jeff Baran, a Democrat, said NRC staff had included the extra safety measures in the draft after years of work, but Republicans had jettisoned them.

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and earthquake hazards that could occur at their sites, the NRC will allow them to be prepared only for the old out-of-date hazards typically calculated decades ago when the science of seismology and hydrology was far less advanced than it is today,” Baran said after the vote.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

NRC Chairman Kristine Svinicki, a Republican, said after the vote that the commission’s work since 2011 has resulted in “tangible safety improvements at every U.S. nuclear power plant.”

Svinicki said that although the Democrats were concerned that the rule ignores flooding and earthquake hazards, “in the view of the commission majority this is not the case.” Regulations already in place already address the issues, she added.

A nuclear power safety advocate said new information showed that plants may experience bigger floods and earthquakes than they are now required to withstand, and that it is possible the commission will not require nuclear plants that face greater hazards to make upgrades.

“Nuclear plants must be protected against the most severe natural disasters they could face today - not those estimated 40 years ago,” said Edwin Lyman, acting director of the Nuclear Safety Project at the Union of Concerned Scientists.