(AP/David Goldman)

Staff at the U.S. Naval Research Laboratory in Washington spent more than 9,000 hours during five months last year preparing and reviewing requests from its scientists and engineers to attend conferences and present research. The tab for taxpayers was $824,000.

The Energy Department’s Los Alamos National Laboratory in New Mexico spent $1.6 million to review similar travel and conference requests during one fiscal year, an increase of $1.4 million from the previous one.

And Los Alamos officials poured $708,500 into updating a travel and expense management system so they could track all the paperwork.

These expenses are among the extraordinary costs that federal agencies say they have incurred in the three years since the Obama administration severely clamped down on employee travel to training and other conferences, after a Las Vegas spending scandal.

[What happened with the GSA in Vegas stymies federal workers]

The Government Accountability Office identified the examples in a study this month of the 2012 policy’s effects on science, technology and engineering researchers at the Defense and Energy departments, which employ more than 129,000 of these experts.

GAO, the watchdog arm of Congress, concluded that travel restrictions at the two agencies have severely curtailed attendance at academic conferences, a frustration felt by employees across the federal government.

The scientific community, which complained early on to Congress and the White House that the travel curbs were diminishing government researchers’ standing in the United States and abroad, was hit particularly hard.

With only shaky assurances that their supervisors will approve their attendance at a conference with a reasonable lead time — or approve the request at all — “scientists and engineers are less likely to submit papers or accept speaking invitations,” GAO found in its 52-page report.

“They do not have assurance that a decision regarding attendance will be made in a timely fashion, DOD and DOE officials told us, because they may be concerned about their standing with peers in their technical communities,” auditors found. As a result, the Defense and Energy departments are worried about recruiting top talent and keeping scientists from leaving for academia or industry jobs.

But the report offers new details on the tangible costs to taxpayers of implementing the travel restrictions, which came after embarrassing revelations by the inspector general for the General Services Administration. Three hundred employees in GSA’s Public Buildings Service took a four-day junket in Las Vegas that featured a mind reader, after-hours parties in loft suites and a bike-building exercise. Lavish conferences held by several other agencies soon came to light.

Although the government has not released data on how much agencies spent on travel and conferences before the crackdown, White House officials have said that the restrictions have saved about $3 billion and have ensured that taxpayers are not paying for more boondoggles.

But employees and their bosses have struggled to work within a new bureaucracy created to make sure that the government spends money wisely.

Defense and Energy department officials have limited data on the labor costs of implementing the travel restrictions, which requires multiple levels of review, even for conferences costing less than $20,000. For those over $100,000, senior officials must sign off, and an event costing $500,000 or more requires a deputy secretary’s signature.

One Los Alamos official told auditors that for a recent American Chemical Society meeting, airfares increased $400 while the conference request was being reviewed, resulting in one attendee’s ticket increasing to $1,400 for a domestic round-trip fare because of a ­last-minute approval.

GAO reviewed the policy’s effect on research labs operated by each military department. At the Energy Department, auditors focused on the National Nuclear Safety Administration and its three national labs, Los Alamos, Lawrence Livermore in California and Sandia, also in New Mexico. The research missions include mitigating existing or emerging threats; developing new technologies to deter U.S. adversaries; managing and securing the nation’s nuclear weapons; and preventing the spread of nuclear weapons and related technology.

Both agencies created ­department-wide “management systems” to track conference expenditures, and some of the military departments and nuclear safety administration labs developed or modified their own systems, auditors said.

For example, Army officials estimated that the cost of deploying software called the “Army Conference Reporting and Tracking Tool” was $658,000. They described the tool as an online application designed to increase efficiency and decrease errors in the conference requesting and reporting process.

Approval for some conferences takes as long as nine months.

In January, the Office of Management and Budget told agencies they could delegate conference approvals to lower-level officials in an effort to make the process less cumbersome and time-consuming

But neither Defense nor Energy department officials told auditors they planned to do so.