WASHINGTON – The chairwoman of the Nuclear Regulatory Commission assured a Senate committee that the nation’s nuclear power plants “continue to operate safely” but drew the ire of a key lawmaker who asserted the agency isn’t doing enough to assure the public’s safety.

Allison Macfarlane, appointed to the commission by President Obama almost two years ago, told the Senate Environment and Public Works Committee that safety standards implemented in wake of the Fukushima nuclear plant breakdown in Japan in March 2011 are progressing as planned.

“The NRC continues to monitor the implementation of the required safety enhancements,” Macfarlane said. “We are seeing the reactors with upcoming fall outages preparing to make modifications to safety systems to provide additional supplies of electrical power and multiple ways to inject cooling water into the reactors and spent fuel pools. They are also positioning additional portable equipment that is arriving at the sites.”

After the Fukushima incident, Macfarlane said, the NRC required reactor licensees to prove they were capable of protecting their facilities from natural disasters. The plants, she said, “are making progress.”

“Additionally, plants have now begun installing additional reliable instrumentation to monitor water levels in the spent fuel pools following a beyond-design-basis event,” she said. “Overall, licensees are making significant progress in implementing our Fukushima-related requirements.”

But in an unusual rebuke from a member of the president’s own party, Sen. Barbara Boxer (D-Calif.), the committee chairman, charged that the NRC has “lost sight” of its stated missions to “ensure the safe use of radioactive materials for beneficial civilian purposes while protecting people and the environment.”

Boxer said the Fukushima Near-Term Task Force, made up of NRC senior staff, recommended 12 measures to upgrade safety in the wake of the Fukushima meltdowns. To this point, the NRC has completed its own action on only four of those proposals and has failed to require reactor operators to complete implementation of any measures. Some reactor operators are still not in compliance with the safety requirements that were in place before Fukushima.

These implementation delays, Boxer said, place “the safety of the American people at risk.”

“Not only does NRC allow that fuel to be stored in the spent fuel pools indefinitely, NRC is considering requests from decommissioning reactor operators for exemptions from emergency response measures designed to protect nearby communities,” Boxer said. “While the Nuclear Energy Institute claimed in a letter sent to me yesterday that these exemptions are granted only when ‘special circumstances’ exist at a facility, the truth is that NRC has never once denied one. It rubber-stamps them every single time a reactor shuts down.”

Boxer expressed particular concern over what she characterized as “the installation of defective equipment” at the San Onofre Nuclear Generating Station in her home state of California, asserting that NRC staff is preparing to allow the re-start of one of the reactors before it had received answers to the safety questions submitted to the facility’s owner, Southern California Edison.

The plant is located in an earthquake zone and a tsunami zone. A fire came within half a mile of the facility so an investigation into San Onofre, she said, is important “to avoid disastrous problems like this in the future.”

“In order for the nuclear industry to maintain the confidence of the American people at a time when it is increasingly challenged by safety and economic concerns, the agency charged with regulating the nuclear industry must always make public safety its number one priority,” Boxer said. “NRC’s recent track record does not inspire confidence.”

During questioning, Boxer asked Macfarlane if the NRC intends to exempt San Onofre, which currently is shut down, from certain safety requirements. Macfarlane refused to answer directly, sparking the chairwoman’s ire and placing Sen. David Vitter (R-La.), the committee’s ranking member, in the unusual position of defending an administration official from the opposing party.

At one point, Boxer pressed Macfarlane on the 12 task force recommendations, asking whether any of them have been implemented and answering her own question by saying, “They haven’t.”

Macfarlane, through repeated interruptions from Boxer, sought to explain that the NRC has prioritized the recommendations and that some should be in place by the end of 2016. But Boxer insisted on eliciting a yes or no answer.

Vitter eventually stepped in.