After Japan's Fukushima nuclear plant melted down in 2011, Nathan Sanfilippo joined a team at the Nuclear Regulatory Commission charged with evaluating what went wrong and determining how to prevent a similar disaster in the United States.

Developing a strategy for the country's safety and Japan's recovery is the sort of assignment that Sanfilippo says allows him to leave work at the end of the day feeling as if his contribution makes a difference.

Sanfilippo and his colleagues at the Rockville-based agency rated their employer among the top federal agencies for job satisfaction in the annual Federal Employee Viewpoint Survey administered by the Office of Personnel Management.

"The leadership here has done a good job of taking the mission of the agency and involving everyone on the staff in that mission," said Sanfilippo, a 33-year-old materials engineer who started working at the commission after his graduation from Penn State 11 years ago.

"There is a lot of trust in the capabilities of individuals."

The NRC, which regulates nuclear power plants and materials, placed second behind NASA in this year's voluntary survey for overall satisfaction.

Seventy-four percent of NASA workers reported that they were satisfied, compared to 72 percent at the NRC.

The Woodlawn-based Social Security Administration showed an overall employee satisfaction of 65 percent.

The Department of Housing and Urban Development and the National Archives and Records Administration tied at 49 percent for the lowest overall satisfaction.

Nearly all respondents in this year's survey indicated that they were willing to put in extra effort at their jobs and that they feel that their work is important, but year-to-year comparisons show a significant decline in satisfaction, according to an analysis by the OPM.

Federal workers have been subjected to a three-year wage freeze, furloughs and other cuts. The web-based survey was conducted before the government shutdown in October.

Across the federal government, 59 percent of workers said they feel satisfied with their job. That indicator dropped four points from 63 percent last year, and is down seven points from 2011.

The results from 37 large agencies were tallied into a Global Satisfaction Index.

"The results show employees are ready and willing to meet the challenges they face and are steadfastly accountable for achieving results and knowing what is expected of them on the job," Katherine Archuleta, the OPM director, said in a statement.

More than 376,500 employees responded to the survey. Employees in 81 agencies were asked their opinions, but the OPM factored only the results for the 37 largest into the Global Satisfaction Index.

Drew Halunen, a spokesman for the National Federation of Federal Employees, said agencies can look toward morale boosters such as work recognition programs to improve job satisfaction.

"While federal employees are not receiving monetary incentives … as they would in the private sector for great work, agencies could develop programs that actively recognize the work of the dedicated federal workforce that it employs," Halunen said in an email. "This kind of recognition is underutilized in most federal agencies.

"But realistically, federal worker satisfaction will be hampered so long as they are continually refused pay adjustments each year to offset cost-of-living increases. Being used as a political punching bag coupled with hemorrhaging employment benefits is leading to reduced satisfaction rates."

Sanfilippo, a native of the Pittsburgh area who lives in North Bethesda, said working for a federal agency has changed since he was hired around the turn of the millennium.

"It is tough; it was a lot easier when you had resources at your disposal, and the agency was in that place for a number of years," Sanfilippo said. He said the NRC has rewarded its employees in "creative" ways, such as by helping them to better balance work and life.