The Nuclear Regulatory Commission is defending its efforts to tighten safety measures at U.S. reactors in a report sent to Congress late last week.

NRC Chairman Gregory Jaczko told Senate and House appropriators the commission has taken "decisive, well-informed regulatory actions" in response to the magnitude-9.0 earthquake and tsunami that crippled Japan's Fukushima Daiichi plant on March 11, 2011.

"I want to assure you that the NRC will continue its diligent efforts to work in an open, transparent manner as we continue to implement the lessons learned from the Fukushima accident," he wrote.

Congress included a provision in the 2012 omnibus spending bill that orders NRC to meet or accelerate safety changes outlined by agency staff in an Oct. 3 paper (Greenwire, Jan. 17). Appropriators also asked the agency for a written update on the one-year anniversary of the Japanese accident.

The NRC accelerated its proposed timeline and issued three orders to address the top-tier safety issues last month.

The orders call on plant operators to shore up emergency backup equipment by 2016 to protect reactors from earthquakes, floods and other natural disasters. Operators must also install equipment on spent-fuel pools to gauge temperature and water levels during an emergency, and ensure vents can release heat and steam to prevent explosions (E&ENews PM, March 9).

The NRC also asked plant operators to reevaluate seismic and flooding hazards at each site using up-to-date information and modeling, and conduct inspections to ensure their facilities can withstand long periods without power. The commission expects to complete a rule in 2014 to address what a nuclear plant operator must do to prevent a meltdown if a reactor loses electricity during an emergency.

But lawmakers have been sensitive to criticism from the Union of Concerned Scientists and the American Nuclear Society, which say the commission isn't moving fast enough to revamp its regulatory framework or expand evacuation zones.

Sen. Bob Casey (D-Pa.) on Friday asked Jaczko in a letter to immediately re-examine the standard 10-mile evacuation zones around nuclear power plants. Casey said the NRC, a year after the Japanese disaster, has yet to release a review of the evacuation zones in the United States.

"One year after Japan's disaster, it is time that millions of Pennsylvanians living in close proximity to nuclear power plants know that the unique characteristics of each plant have been taken into account in the development of evacuation plans," Casey said. The senator also said the NRC should consider imposing evacuation zones crafted for individual plants.