The chairman of the US Nuclear Regulatory Commission (NRC), particle physicist Gregory Jaczko, has announced he is to resign. The announcement comes a year after congressional Republicans objected to his leadership in phasing out the proposed nuclear-waste repository in Yucca Mountain in Nevada. It is unclear when his resignation will become effective, with the Obama administration announcing its intention to nominate a new NRC chair soon, who must also receive Senate backing.

According to regulations, the NRC has five commissioners who regulate and license nuclear power, but the chairman has ultimate legal authority. Jaczko had spent seven years as a commissioner, including three as chairman, with his term set to expire in June 2013. "I have decided this is the appropriate time to continue my efforts to ensure public safety in a different forum," he declared in an official statement. "This is the right time to pass along the public-safety torch to a new chairman who will keep a strong focus on carrying out the vital mission of the [NRC]."

"Serious damage"

Jaczko's time as chairman had recently been hit by a number of accusations over the handling of the $10bn Yucca Mountain facility – a site that Congress had designated as the sole potential location for a national deep underground nuclear-waste dump before funding for the repository was terminated in 2011. After allegations by commission staff that Jaczko had "unilaterally and illegally" stopped a safety-evaluation report on the facility's design, last June Hubert Bell, the NRC's inspector general, accused Jaczko of "using forceful management techniques to accomplish his objectives" while noting that he had operated within the law.

In October Jaczko's four fellow commissioners – George Apostolakis, William Magwood, William Ostendorff and Kristine Svinicki – then wrote a letter to the White House accusing Jaczko of "causing serious damage" to the commission that could affect safety at US nuclear plants. Indeed, Bell is known to be preparing a report that is expected to repeat some of the commissioners' accusations.

Svinicki, the only female commissioner, told Congress last December that Jaczko had created a working environment in which women felt especially threatened. Jaczko has categorically denied that charge. Early this month the Obama administration nominated Svinicki, a former aide to Republican senators, for another term as an NRC commissioner.

Jaczko says that throughout his time at the NRC, the agency finalized new nuclear-safety regulations, completed the development and implementation of a safety-culture policy statement, as well as helping to make the NRC more open and transparent. "We stand as a stronger and more decisive regulator now because of these years of efforts," he says. Jaczko also took a leading role in the NRC's response to last year's nuclear incident at Fukushima, Japan.

Vermont Senator Bernie Sanders, a socialist who supports Democratic policies, praised Jaczko for "his efforts to hold the nuclear industry accountable". Republican Senate minority leader Mitch McConnell of Kentucky, however, said that "the only thing surprising about [Jaczko's] resignation is the fact that the Obama administration has remained silent for more than a year after allegations of Jaczko's offensive behaviour surfaced".