Lawmakers told Friedman they were concerned about a July 2012 security breach at a federal nuclear weapons complex and an IG report that detailed expensive contractor travel fees.

How the agency remedies the breach at its Y-12 National Security Complex in Oak Ridge, Tenn. is an important test in how DOE improves its relationship with contractors, Friedman said.

An August 2012 DOE Inspector General report found “multiple system failures on several levels” allowed three trespassers who “defaced the building” to approach Y-12 undetected.

The incident alarmed both Republicans and Democrats who worried DOE might be failing to adequately protect the nation’s nuclear weapons stockpile, which is one of the department’s central missions.

Friedman told lawmakers on Thursday that Y-12 “was thought to be the Ft. Knox of the weapons complex.” He said his office was closely monitoring DOE’s progress on strengthening its security protocol and its interactions with contractors at Y-12.

Senior DOE leadership has “gone to great lengths to make sure that the issues we identified at Y-12 have been addressed,” Friedman said.

While Y-12 is one of the more high-profile security blunders DOE experienced in recent years, Friedman said DOE’s trouble balancing its large contractor workforce with agency goals dates back to the 1940s-era Manhattan Project, the federal atomic bomb research program.

“It’s an issue which has not been resolved in the many years that I’ve spend looking at the Department of Energy system. That, to me, is the prime recommendation,” he said, adding that he has given DOE “almost a whole inventory of recommendations” on the topic.