Allison M. Macfarlane, chairman of the Nuclear Regulatory Commission, announced Tuesday that she will resign to take a teaching job at George Washington University.

Macfarlane, who still has more than three years left in her term, said she would leave Jan. 1 and become director of the university’s Center for International Science and Technology Policy. In an interview, she called it “a great offer,” but people close to her said she also stepped down to spend time with her ailing mother.

“I accomplished what I wanted to do at the NRC,” Macfarlane said, “and I really miss academia.”

Trained as a geologist and a former professor at George Mason University, Macfarlane has served as NRC chair since July 9, 2012, and has restored a more collegial atmosphere in an agency that had been roiled by controversy over the management style of her predecessor, Gregory B. Jaczko.

Macfarlane has also overseen the implementation of new safety measures prompted by the tsunami that severely damaged Japan’s Fukushima Daiichi nuclear complex in 2011. Those included additional protective equipment at reactor sites, sturdier seismic and flood protection at power plants, and progress on hardening venting systems at plants that had a design similar to Fukushima’s.

But Macfarlane has also lost several votes at the five-member commission, some of them of particular importance. She sided with the NRC staff’s recommendation that reactors add filtered vents that can capture radioactive materials while allowing steam and hydrogen to escape in an emergency. This was one of the failures at Fukushima. She lost that vote, 3 to 2.

She also voted to expedite the transfer of spent fuel rods from cooling pools to dry casks better able to withstand a disaster at nuclear power plants. She lost that vote, 4 to 1.

Macfarlane differed with the NRC staff over long-term waste storage, and she dissented from a commission statement because she felt that nuclear waste should be moved to a centralized repository and not be stored indefinitely at reactor sites. Under Macfarlane, a new rule on long-term storage was adopted to replace a rule thrown out by an appeals court in the District.

Macfarlane also faced demands from Congress, including both parties. Sen. Barbara Boxer (D-

Calif.) wanted the NRC to release internal documents about the San Onofre Nuclear Generating Station, where leaks in steam turbines led to the eventual closure of the reactors there.

Macfarlane’s announcement comes one month after the Senate confirmed two new commissioners, Jeff Baran, an aide to departing Rep. Henry A. Waxman (D-

Calif.), and Stephen Burns, a former NRC general counsel.

“We would certainly agree that she did an effective job of restoring collaboration and collegiality among the commissioners, which is important for the agency’s credibility,” said Steven Kerekes, a spokesman for the Nuclear Energy Institute.

In a statement, Macfarlane said: “I came to the Commission with the mission of righting the ship after a tumultuous period and ensuring that the agency implemented lessons learned from the tragic accident at Fukushima Daiichi, so that the American people can be confident that such an accident will never take place here.”