WASHINGTON (AP) -- The embattled chairman of the Nuclear Regulatory Commission resigned Monday after a tumultuous three-year tenure in which he pushed for sweeping safety reforms but came under fire for an unyielding management style that fellow commissioners and agency employees described as bullying.
Gregory Jaczko stepped down ahead of a potentially blistering report due out soon from the agency's inspector general, which has been investigating his actions for more than a year.
Jaczko, 41, led a strong response to the nuclear disaster in Japan and was a favorite of industry watchdogs, who called his emphasis on safety a refreshing change from previous agency chiefs who were close to the nuclear industry or who came from it.
But scientists, fellow commissioners and many rank-and-file staffers said Jaczko had created a chilled working environment at the NRC, which oversees safety at the nation's 104 commercial nuclear reactors.
In an extraordinary public rebuke, four fellow commissioners sat next to Jaczko last December and told Congress he was an intimidating bully whose actions could compromise the nation's nuclear safety. The four commissioners said women at the agency felt especially threatened.
The commissioners -- two Democrats and two Republicans -- sent a letter to the White House last fall expressing "grave concern" about Jaczko' s actions, which they said were "causing serious damage" to the commission.
No disciplinary action was taken against Jaczko, who strongly denied the allegations.
An inspector general's report released last summer said Jaczko had intimidated staff members who disagreed with him and withheld information from members of the commission to manipulate their decisions on critical votes. A follow-up report is due in the next few weeks.
Jaczko said in a written statement that it was the right time to step down, adding that he hoped his successor would keep a strong focus on safety. Jaczko said he will continue to lead the commission until his successor is confirmed.
Jaczko did not mention the bullying allegations in his statement, but said he was "truly humbled by the agency's success" in responding to issues ranging from the Japan crisis to severe incidents at U.S. reactors caused by flooding, earthquakes and tornadoes. "In addition to this vigilant oversight, together we identified and began to implement lessons learned from Fukushima and completed our rigorous safety reviews for the first new reactor licenses in 30 years," he said.
White House spokesman Clark Stevens said Monday that President Barack Obama appreciates Jaczko's service and intends to nominate a new chairman soon.
Jaczko, a Democrat and former aide to Senate Majority Leader Harry Reid of Nevada, was the agency's public face during its response last year to an earthquake and tsunami that triggered nuclear meltdowns at the Fukushima Dai-ichi nuclear plant in Japan. He also took responsibility for recommending that U.S. citizens living in Japan evacuate an area larger than what U.S. communities near nuclear facilities prepare for, a decision that lawmakers and the NRC's advisory board questioned.
Jaczko, who has served on the NRC since 2005, was named by Obama to lead the independent agency in 2009. Since then, he has made a series of decisions to delay or halt work on a proposed nuclear waste dump at Nevada's Yucca Mountain, a project Obama had made a campaign promise to kill.
Jaczko's actions have been criticized by congressional Republicans, his own scientific staff and the NRC's inspector general. The IG report found that Jaczko acted within his authority and broke no laws. But it also concluded that to get his way on the issue, he failed to be forthcoming with other commissioners.
Reid, the leading opponent of the Yucca Mountain nuclear waste site, praised Jaczko's service to the commission on Monday.
"He dedicated his tenure to improving the safety of nuclear energy, and his leadership during the Fukushima nuclear crisis protected millions of Americans," Reid said in a statement.
Sen. James Inhofe, R-Okla., the senior Republican on the Senate Environment Committee, said Jaczko's decision to resign was the right one. With his resignation, "the NRC can focus on its mission of safety without the distractions of Jaczko's inappropriate behavior," Inhofe said.
Janet Kotra, a senior scientist and project manager on the proposed Yucca waste dump, called Jaczko's resignation an "enormous relief." A 28-year NRC employee, Kotra said the agency's reputation as an independent safety authority had been greatly damaged under Jaczko.
"Now, the NRC can begin to rebuild its reputation," she said.
Inhofe and other Republicans said Jaczko's impending departure reinforced the urgency of Senate action to confirm Republican Kristine Svinicki to new term on the NRC.
Obama nominated Svinicki, a nuclear engineer and former Senate GOP aide, for another term earlier this month despite objections from Reid and Sen. Barbara Boxer, D-Calif., chair of the Senate Environment Committee.
In his three years as chairman, Jaczko was often the lone dissenting vote on the five-member panel, including a recent vote to approve the first nuclear power plants built in the U.S. in more than 30 years. Jaczko opposed a license for the Atlanta-based Southern Co., saying he wanted to wait until the commission approved safety changes prompted by the Japan disaster.
Marvin Fertel, president and CEO of the Nuclear Energy Institute, an industry group, said he recognized Jaczko's commitment to set high safety standards.
"We have had differences with the chairman on how best to achieve our mutually shared safety goals. But to his credit we've always had open lines of communications and a willingness to respectfully discuss the issues," Fertel said in a statement.
Dale Klein, a former NRC chairman and commissioner who served with Jaczko, said Jaczko had turned the agency "upside down." Klein, a Republican, was appointed to lead the agency by President George W. Bush in 2006 and left the NRC in 2010.
"It has been unusual that you have a chairman that so often loses on a 4-to-1 vote. That is not leadership," Klein said in an interview. "I hope a new chairman can get picked quickly and NRC can get on with its task of protecting the public and the environment."
Associated Press writer Dina Cappiello in Washington contributed to this story.