Gregory Jaczko, chairman of the U.S. Nuclear Regulatory Commission, announced his resignation this week, but he is still making pointed comments about the need to strengthen regulations to ensure nuclear power plants are safer.

“I think the Fukushima event was a wake-up call, hopefully for everyone,” Jaczko said in a news conference today, referring to the earthquake- and tsunami-triggered nuclear plant accident in Japan on March 11, 2011,

“I think there were people throughout this industry who had come to the belief that an accident of that magnitude simply was never going to happen, that we had really come to the point at which we’d eliminated that,” Jaczko said. “I’ve always tried to do my job without making that assumption.”

There are hopeful signs for improvement, Jaczko said. After the disaster in Japan, he said, there has been a shift in the industry and within the NRC to “put more focus on safety.”

However improvements have been too slow, he argued. “I think we don’t do a good enough job identifying issues [and] bringing them to resolution in a timely way,” since they sometimes take 10 to 15 years to improve, Jaczko said. “It’s not getting the issues resolved so the public can feel comfortable, it’s not freeing up resources to tackle the next round of issues that will come in front of us. So that’s an area where we need to continue to make progress.”

Jaczko has been known for taking a more cautious approach than the other commissioners.

In one of his most contentious moves, Jaczko canceled the review of a plan to store nuclear waste at Yucca Mountain, a federal site in Nevada. Under the plan, highly radioactive waste would be transported from across the country to the site, then buried underground to protect people and the environment while the radioactivity died down over many thousands of years. But this waste repository has been bedeviled by controversy, and gained many opponents.

In his actions on Yucca Mountain and his strong response to the Fukushima disaster, Jaczko has come under fire for alleged aggressive behavior and an abrasive management style. The complaints have led to two internal investigations.

When asked about these conflicts, Jaczko said little in the news conference, but explained his outlook this way: “We want debate, we want discussion, we want to have engaging conversation…. I’m a passionate person [and] I care passionately about nuclear safety, so I enjoy the opportunity to engage my colleagues in debates and discussions.”

George W. Bush nominated Jaczko to be one of the NRC’s five commissioners, and he has served on the commission since 2005, and as chairman since 2009.

Jaczko’s resignation is contingent on a new chairman being named and confirmed by Congress, he said at the news conference.

The White House said on May 21 that it would nominate his replacement “soon.” Jackzo’s term is due to end in June 2013, but if a new chairman is not confirmed by Congress by then, “I’ll deal with those issues at that time,” Jackzo said today.

Senate majority leader Harry Reid, a Nevada Democrat and longtime staunch opponent of Yucca Mountain as a nuclear waste repository, said that he would be fine with Jaczko—one of his own former aides—remaining in his position indefinitely. “We hope to have a replacement before” the end of Jaczko’s term, Reid said. But he added, “if something doesn’t work out, he can always be re-nominated.”