The head of the Nuclear Regulatory Commission has strategically withheld and controlled information to steer decisions his way on closing a proposed radioactive waste dump, according to an internal investigation.

The seven-month inquiry by the agency's inspector general says that NRC Chairman Gregory Jaczko was "not forthcoming" to other commissioners when he decided to shut down in October the technical review of the Energy Department's application for an underground nuclear waste dump at Yucca Mountain in Nevada.

But the investigation found no instances in which he broke the law, as some have alleged.

Republican leaders of the House Energy and Commerce Committee requested the report, which was obtained by The Associated Press.

Jaczko said the report's findings "reaffirm that my actions have been and remain consistent with established law, guidance and my authorities as chairman."

He called the shutdown of Yucca Mountain a complicated issue, adding that all NRC chairmen must make "difficult and sometimes controversial decisions."

Republicans and many Democrats outside Nevada favor creation of single storage site for nuclear waste, but the Yucca Mountain project is fiercely opposed by Nevada lawmakers, including Senate Majority Leader Harry Reid, who has vowed to do everything in his power to kill it.

President Barack Obama opposed the Yucca Mountain site in the 2008 campaign and has moved consistently to kill it since taking office in 2009.

Jaczko, who has chaired the NRC since May 2009, worked as a science adviser to Reid before joining the NRC in 2005.

The license for the Yucca Mountain, which has been in development for nearly 30 years and cost more than $15 billion so far, has been in limbo since last June, when a licensing board independent of Jaczko and the rest of the commission rejected the Obama administration's request to withdraw the project application. Jaczko has yet to schedule a final vote from the five-member commission on the matter.

In the meantime, the report says, Jaczko first told his staff to proceed with the review but in October changed course and instructed them to halt work on the project.

The 46-page report by NRC Inspector General Hubert Bell also delves into Jaczko's management style, saying he often lost his temper and badgered staff members who disagreed with his positions. A number of those interviewed said Jaczko would threaten to withhold foreign travel or to contact the Obama administration as means of gaining support on issues.

Jaczko knew his decision to shut down the technical review of Yucca Mountain, which would be used by the board to evaluate the license, "would be controversial and viewed as a policy decision for full commission consideration," the report says. "Therefore ... he strategically provided three of the four commissioners with varying amounts of information about his intention."

Lawmakers from both parties have criticized Jaczko for what they say is an overly secretive style and accuse him of acting unilaterally on the commission's behalf. They cite several examples, including Jaczko' s declaration in March that Japan's nuclear crisis constituted an emergency in the United States.

Their sharpest criticism is reserved for his handling of the divisive plan to shut down Yucca Mountain, about 100 miles northwest of Las Vegas.

The NRC is considering a request by the Energy Department to shut down the proposed waste site and has begun initial steps to implement the shutdown. Even so, Jaczko has said the five-member commission has not cast a final vote on the issue and has no timeframe to make a decision.

Three NRC commissioners told Congress last month that they have cast what they consider substantive votes on the matter.

That apparent contradiction mystified and enraged members of Congress, who said they cannot get a straight answer from the NRC on Yucca.

"The level of non-information is frustrating," said Rep. Lee Terry, R-Neb. "I'm very disturbed."

Rep. Joe Barton, R-Texas, accused Jaczko of "playing some kind of foot-dragging game" and intentionally delaying a decision on Yucca Mountain.

Before becoming NRC chairman, Jaczko was a member of Reid's staff. But he denied that the Nevada Democrat or anyone else influenced his decisions on Yucca Mountain.

"It was in no way a political action or intended to reference any other political figure or direction from any other political figure," he told the House Energy and Commerce Committee at a hearing last month.

In an unusual move, Jaczko sought to get ahead of the inspector general's report, which has not been released to the public, with a statement late Wednesday. He said the investigation reaffirmed that his actions have been consistent with the law and his authority as chairman.

But he acknowledged to the IG that he at times lost his temper and used "forceful" management techniques.

In an interview Thursday with the AP, Jaczko defended his tenure his as chairman and his sometimes hard-charging style, which he said comes from a deep-seated belief in the agency' mission to ensure safety of the nation's 104 commercial nuclear reactors.

"I believe passionately and strongly about nuclear safety, and I take that responsibility very seriously," he said.