Albuquerque, N.M. ? The director of the Los Alamos nuclear weapons lab announced his departure Friday after two tumultuous years during which he made enemies with his hard-nosed efforts to stop financial abuses and security lapses.

Pete Nanos will be replaced May 16 by an interim director who will oversee the lab until the University of California’s management contract with the government expires in September.

Nanos did not specify why he was leaving. His tenure was the shortest since the lab was created during World War II to build the atomic bomb.

“While there have been many challenges, I believe there have been many more successes, not so much because of what I may have done, but because of the men and women who care so much about this great institution,” he said in a statement.

Nanos’ boss, University of California President Robert C. Dynes, said Nanos did a “remarkable job under extraordinary pressures and circumstances” and that Los Alamos was a “stronger, safer and better-managed laboratory today.”

Some lab workers celebrated news of Nanos’ departure at a restaurant.

“Every table is packed, and the beer is flowing,” said Todd Kauppila, who was fired for his role in the case of two classified computer disks that were mistakenly thought to be missing — an incident that infuriated some lab employees.

Nanos, a former Navy vice admiral, inherited a host of problems at Los Alamos, including credit card fraud and equipment theft. He took office vowing to “drain the swamp” and restore public confidence.

Nanos replaced top managers, instituted new purchasing rules and took inventory of lab property — moves that garnered high marks from the state’s congressional delegation and Gov. Bill Richardson, who is a former energy secretary.

Last summer, when the two classified disks supposedly vanished, Nanos shut down all classified work and blamed “cowboys” who disobeyed rules on the handling of sensitive material.

It was finally determined the disks were not missing at all; there was an inventory error. The Energy Department said the seven-month work suspension cost as much as $367 million.