Promptly following Senate approval of her nomination, and just seven weeks after her predecessor announced his resignation, Allison Macfarlane was sworn in as the leader of the country's top nuclear regulator.On Monday, she assumed the post from former Nuclear Regulatory Commission Chairman Gregory Jaczko, who announced his resignation in May amid allegations of abusive behavior made by his colleagues and fellow commissioners. He consistently denied bullying those he worked with, while an NRC inspector general report confirmed a number of people at the agency said they felt intimidated during his time as chairman.Macfarlane will serve the remainder of Jaczko's term, ending June 30, 2013.“The agency faces multiple challenges. I look forward to working collegially with my fellow commissioners and the excellent, dedicated staff at the NRC to address these issues,” she said in an NRC statement announcing her joining the commission.A geologist, Macfarlane holds a lengthy resume in academia and most recently became involved in national nuclear policy as a member of the Blue Ribbon Commission on America's Nuclear Future. That advisory body made recommendations for disposing of tons of spent nuclear fuel now stored at individual nuclear plants around the county. Her previous public service included participation on National Academy of Sciences panels on non-proliferation issues and nuclear energy. Some of her research published in a 2006 book examined technical challenges to the now-defunded Yucca Mountain waste repository in Nevada.According to the NRC, she is the first person with a background in geology to join the commission. She is the 15th person to lead the NRC and the third woman to do so.